CHAPTER 3 REVIEW OF LITERATURE

3.1. Crop: The banana is evolved in the humid tropical regions of North-Eastern Asia with as one of its centers of origin. The modern day edible are a mix of wild and cultivated, species and hybrids associated with acuminata and but is the most widespread of the species in section Musa (Daniells et al., 2001).The banana is the subsequent most essential fruit crop in India after that of mango. Its availability, affordability, variety, tastes, medicinal and nutritive values make it the much loved fruit among all people in the world. It is a very trendy fruit because of its low cost and more nutritive value. Banana is consumed in cooked or fresh condition from both as ripe and raw fruit. 3.2. Different varieties of banana: (Perrier et al., 2011) There are more than 400 varieties of bananas in the world, but only a few are commercially grown on a large scale in all over the world. These are , Giant Cavendish, Dwarf Cavendish Lacatan, Robusta, Gross Michel etc. There are other varieties like, Lady Fingers (or Baby bananas), Apple banana and with rare occurrence. The plantains of banana are green, large cooking variety about 30-40 cm long. Around 20 cultivars like , Dwarf Cavendish, Robusta, Monthan, Nendran, Red banana, Nyali, Safed Velchi, Mysore, Basarai, Shrimanti, Rajpuri, Ardhapuri, Rasthali, Karpurvalli, and Karthali are being mostly grown in India (Chandel and Agrawal, 2000). In India, banana is grown under diverse conditions and production systems. Selection of varieties therefore, is based on the various kinds of needs and situations. The Grand Nain is a very popular variety and most of the farmers preferred this variety for banana cultivation. Bunches of banana fruits have well spaced hands with straight orientation, and are bigger in size. The fruit Grand Nain variety developes attractive uniform yellow color with better shelf life and quality than other cultivars like Robusta, Williams and Gross Michel. Among the leading cooking varieties grown in India, Nendran in and Monthan in (Chandel and Agrawal, 2000) are very popular. Bananas are mostly dessert types used for table purpose, while plantains are cooking types or dual purpose varieties. The major and important varieties of banana belong to different genomic groups cultivated throughout the India are as follows (William, 1992):

10

Dwarf Cavendish (AAA): It was first known from China and widely cultivated, especially in the Canary Island, East Africa and South Africa. This variety is popular as commercial cultivar grown extensively as well as table and processing purpose in the states of , Maharashtra, Gujarat, Bihar, , and in India. From the group of Cavendish, 'Basrai' is a very foremost commercial variety in the Maharashtra. Their sizes of bunch, length of fruit are quite good though the keeping quality is less. The average bunch weight is about 15-25 kg banana with greenish in colour even the fruits are ripened. Another type i.e. Gandevi selection known as 'Hanuman' or 'Padarre' is gaining importance inspite of its longer crop duration. Dwarf Cavendish is an extremely successful banana cultivar but highly susceptible to Yellow Sigatoka spot disease in a commercial cultivation. Robusta (AAA): Robusta (AAA) is a semi-tall variety, mostly grown in Tamil Nadu with semi tall variety and also useful in Maharashtra, Karnataka and Andhra Pradesh for table purpose. It is a highly productive and to produce bunch of large size with about 25-30 kg weight and well developed dark green fruits turn bright yellow after ripened. Fruit of this verity is very sweet with a good quality. Robusta is highly vulnerable to Sigatoka leaf spot disease in humid tropics condition. Rasthali (AAB): It is a commercially growing medium tall variety from Tamil Nadu, Kerala, Karnataka, Bihar and Andhra Pradesh. The colour of fruit is yellowish green then pale yellow to golden yellow after ripened. Fruit is very tasty with a good aroma and mostly use for table purpose. It is susceptible to Fusarium wilt, so that requires cover to protect fruits bunch from sun cracking and formation of hard lumps in fruits. Poovan (AAB): It is a most important commercial cultivar grown throughout the country such as in Kerala, Tamil Nadu, Andhra Pradesh and North Eastern area. Tamil Nadu is the leading manufacturer of Poovan cultivar due to its climatic and soil situation. Poovan is also cultivated for leaf industry overall Tamil Nadu and in some areas of Kerala. Fruit is firm, slightly acidic and typical sour-sweet smell. Fruits turn to gorgeous golden yellow after ripening. The plus points of this variety are medium sized fruit bunch, closely packed, good quality. But it is highly susceptible to some viral diseases

11 such as Banana Bract Mosaic Viral (BBMV) disease and Banana Streak Virus, (BSV), which cause significant reduction in yield. Nendran (AAB): This variety is well popular in Kerala as well as commercial cultivation of Nendran has picked up quickly in Tamil Nadu in the recent past years. Nendran is known to display considerable diversity in plant height, pseudostem colour, absence or presence of male axis, bunch size (12-15 kg), etc. Fruits have a separate neck with broad green skin turning polish yellow after ripening. It is greatly susceptible to Nematodes, Borers and Banana Bract Mosaic Virus (BBMV). Red Banana (AAA): It is the most important and very costly variety of Tamil Nadu and Kerala. Red Banana is also accepted in Andhra Pradesh, Karnataka and some area of Western and Central India. In the state of Bihar it is well known as a Lal Velchi as well as in Karnataka as a Chandra Bale. It is a healthy plant with bunches of 20-30 kg weight with good managing practices. Fruits are sweet, orange yellow coloured and with a pleasant fragrance. It is very much susceptible to some diseases like Fusarium wilt, nematodes and Bunchy Top Virus. Ney Poovan (AB): It is the choicest diploid choicest cultivar, which is under commercial cultivation on a big scale particularly in Tamil Nadu and Karnataka. In the state of Kerala it is grown in backyards and now shifting to large scale cultivation. Ney Poovan is a slim plant bearing bunches of about 15-30 kg. Fruit is highly aromatic, tasty, powdery, rigid golden yellow with a very excellent quality. It is tolerant to Sigatoka leaf spot but susceptible to Banana Bract Mosaic Virus and Fusarium wilt disease. Virupakashi (AAB): It is a very best, vigorous and hardy variety in especially grown for table purpose in Palani and Shevroy hills of Tamil Nadu state. Fruits are a typical blended; possess a lovely aroma and wonderful taste. Virupakashi has many ecotypes like 'Sirumalai', 'Vannan', 'Kali' etc. well suited for cultivation in plains. It is susceptible to Banana Bunchy Top Virus (BBTV). Pachanadan (AAB): It is a popular variety for its cooling effects in hot tracts in summer especially cultivated from Tamil Nadu. After 11-12 months weight of bunch ranges from 12-15

12 kg. This variety is susceptible to wilt disease but tolerant to Sigatoka Leaf Spot and Banana Bunchy Top Virus (BBTV) diseases. Monthan (ABB): It is a fairly tall and robust plant bearing bunches of 18-20 kg after 12 months and widely cultivated variety for processing. Fruits are stocky, bold, knobbed and pale green in colour and the skin is usually green. The clones of Monthan namely 'Kanchi Vazhai' and 'Chakkia' are newly becoming popular in Tamil Nadu. It is also cultivated for production of in Trichy and Tanjore (districts) of Tamil Nadu. It has many enviable characteristics like immunity to Banana Bunchy Top Virus (BBTV) diseases, but it is very susceptible to Fusarium wilt disease of banana. Karpuravalli (ABB): It is grown in medium rich soils with good table purpose. It is commercial cultivated in Central and Southern districts of Bihar, Kerala and Tamil Nadu in India. Karpuravalli is the sweetest among Indian bananas and occasionally seeded depending on the seasonal variability. It has ash coated golden yellow and sweet fruits. It is highly susceptible to diseases like wilt disease and tolerant to Leaf Spot disease. Safed Velchi (AB): It is a very good quality fruit for table purpose mostly cultivated in the Thane and Nasik districts of Maharashtra and Karnataka. This is medium sized banana variety with slender yellowish green pseudostem, reddish petiole margin, big and sweet fruits. The weight of average bunch is about 12 kg that is about 160 fruits/bunch. Grand Nain (AAA): It is a Cavendish variety with highly yielding property introduced to India from Israel. The growth of plant is about 6.5 to 7.5 ft height. The fruits of Grand Nain banana variety are tasty to eat with good quality compared to our native varieties. characteristics of Grand Nain variety are high yield is about 30 kg per plant, long cylindrical fruits with less curvature, good quality, attractive yellowish green color. In India, three systems of banana cultivation are in use viz, irrigated or wetland cultivation, homestead or backyard cultivation and rainfed hill cultivation. There are large numbers of cultivars more than 50 that are commercially cultivated all over India. Important cultivars cultivated in world as well as especially in India includes Dwarf Cavendish (AAA), Robusta (AAA), Monthan (ABB), Poovan (AAB), Nendran (AAB), Red banana (AAA), Nyali, Safed Velchi (AB), Basrai (AAA),

13

Ardhapuri (AAA), Rasthali (AAB), Karpurvalli (ABB), Udhyam (ABB), and Grand Nain (AAA) etc. Exotic Varieties of banana: The exotic varieties of banana (Table. 3.2.1.) found in different countries are as follows: Table. 3.2.1. Exotic varieties of banana from different countries. Sr. No. Name of the Exotic varieties country 1 USA Dwarf Cavendish, Giant Cavendish, Pisang masak hijau, Ice Cream, 'Enano Gigante, Macho, Orinoco 2 China Dwarf Cavendish 3 South Africa Dwarf Cavendish, Golden Beauty 4 Australia Robusta, Williams, Cocos, East Africa 5 Bluggoe, Maricongo, Common Dwarf 6 Philippines Common Dwarf, Philippine Lakatan 7 Taiwan Giant Cavend 8 Brazil Robusta, Santa Catarina Silver, Brazilian

The most widely distributed banana cultivar is 'Dwarf Cavendish' (Ploetz et al., 2007). 3.3. Food and Nutritive value of banana: The banana has good nutritive value with excellent source of carbohydrate, vitamin B, potassium, phosphorus, calcium and magnesium etc. The banana fruit is very easy to digest, free from cholesterol and fat. Powder of banana fruit is useful as a first food of baby. It is also helpful to reducing risk of heart diseases and doctors also recommended for patients which are suffering from arthritis, high blood pressure, ulcer, gastroenteritis and kidney diseases. Plantains or cooking bananas are rich in starch and have a chemical composition similar to that of . Sugar content in banana has been reported to 12.23g/100g of total weight of banana. The banana fruit is one of the high calorie tropical fruit, which provides 90 calories of energy per 100g of fruit. Besides, it contains good amounts of health benefitting antioxidant, sugars, minerals and vitamins. Therefore, banana is the most important cash crop in the world.

14

3.4. Production of Banana: Global and Indian scenario: Global Scenario: The bananas are produced in 130 countries. The 12% of total world production is exported and 88% is consumed domestically. The present scenario of average productivity of banana in world is 20.7MT/hector (ha). Ten major countries contribute two-thirds to the total global production. India produces 25.6% , it is followed by China (10.2%), Philippines (8.9%) and Equador (6.8%). Other leading producers are Brazil (6.7%), Indonesia (6.0%), Angola (2.9%), Guatemala (2.6%), United Republic of Tanzania (2.4%), (2.1%) and others countries (25.9%) (Food and Agriculture Organization of the United Nations (FAO), 2014, for Indian horticulture database 2013). Banana and plantain, are continuously exhibiting a spectacular growth worldwide, primarily for their fruit, and to a lesser extent to make fiber, and as ornamental plant. India is the largest producer of banana in the world constituting almost 25.6% of total global production. The banana is fifth largest agricultural product in all over the world later than cereals, sugar, cocoa and coffee. There has been a considerable increase in productivity of banana between 2001 and 2009 in India and China owing to technological adoptions. The productions of banana in Ecuador, Columbia and Costa Rica have shown a declining trend throughout this period. The advantage of this fruit is its availability round the year. It is cultivated in 130 countries in tropical and sub-tropical regions of mostly developing economics in the world. The leading banana manufacturer countries in the world are India, Brazil, Equador, China, Philippines, Columbia, Srilanka, Indonesia, Costarica and Mexico which are accounting for 58 per cent of world contribution. The global production of bananas is estimated to be around 48.9 MT. India is the largest producer of banana with a production is about 25.6% of it. Perrier et al., 2011 used linguistic, genetic and archaeological data to decide the locations of banana groups. They suggested three contact areas of M. acuminata subspecies where the development of domesticated diploids took place. The northern areas of bananas are M. malaccensis, M microcarpa and M. errans in South East Asia, Borneo and the Philippines. The eastern contact area with M. errans and M. banksii between the Philippines and New Guinea and the Southern contact area with M. banksii, M. zebrina and M. microcarpa situated between New Guinea and Java. It seems clear that the islands of are the origin for all bananas and subsequently the

15 different groups migrated to different areas of the world. Banana production in Arabian countries accounts for 2% of the total world production of banana and 1.5% of total area harvested (FAOSTAT, 2010). Secondary and tertiary distribution followed and produced six identifiable geographical areas each with a high density of specific cultivars (Buerkert et al., 2009): (1) Genotypes AA and AAA in the triangle between Indonesia, the Philippines and Melanesia with an excellent density of AA cultivars in and around New Guinea. (2) Highland AAA bananas in the Great Lakes region of East Africa. (3) AAB plantains in the rainforest zone of Africa. (4) AAB Maia Maoli-Popoulu-Iholena cultivars in Oceania (5) AB and other AAB cultivars in South India. (6) ABB cultivars in the Vietnam and Philippines, Northeast and South India. Buerkert et al., 2009 hypothesized that the AAA (genotype) cultivar recently discovered in the Upper Tiwi Valley of Oman reached via East Africa, most likely Zanzibar, Madagascar or the Comoros islands where many AA and AAA cultivars are obtainable. The banana plants are dispersed mainly on margins of tropical rainforests (Wong et al., 2002). Rwanda is the highest banana consumptive country in the world (197 kg per capita per year) (Frison and Sharrock, 1999). Biodiversity International, 2012 analyzed eighty eight percent of bananas produced globally is consumed locally. Boivin and Fuller, 2009 stated that in general, data indicate that the early third millennium saw the overture of different crops including banana plant from Africa, South and Southeast Asia to the Arabian county. The global production of banana is around 103632349 MT out of which India contributes 25.6%. Besides India, other major banana producing countries are Ecuador, Philippines, Brazil, Indonesia and China. The table given below shows the major banana producing countries in the world (Table. 3.4.1).

16

Table. 3.4.1. Major banana producing countries in world Country Area in HA Production in MT Productivity MT/HA India 802566 29724548 37.0 China 400000 10550000 26.4 Philippines 454179 9225998 20.3 Ecuador 210894 7012244 33.3 Brazil 481116 6902184 14.3

Indonesia 105000 6189052 58.9 Angola 115749 2991454 25.8 Guatemala 66000 2700000 40.9 United Republic 442190 2524740 5.7 of Tanzania Mexico 72617 2203861 30.3 Others 1883780 26823720 14.2 World + (Total) 5034091 106847801 21.2

(Source: FAO Website -February 2015 (Data for 2012, 2013 N/A) and for India Data - (Data for 2013-14) Department of Agriculture & Cooperation).

Indian Scenario: In India banana is being cultivated in climate ranging from humid tropical to dry mild subtropics through selection of suitable varieties. Injury for banana occurs at temperature below 12ºC in winter season, high velocity of wind and heavy rainfall. In India banana ranks first in production and second in area of fruit crops. It accounts for 13% of the total area and 33% of the production of fruits. Within India, Maharashtra has the highest productivity of 65.70 metric tons /ha against national average of 30.5 tones/ha. (National Horticulture Board, India, 2008-09). India ranks first in banana production, contributing about 25.6% in world pool of banana Production (Biswas and Lalitkumar, 2010). Wahengbam et al., 2014 reported that banana is the one of the most significant fruit plant in Manipur which is associated with the culture. There are many indigenous banana varieties in Manipur as wild and cultivated forms, some banana Pseudostem and male buds are used as a medicinal plants for women. A little group is very costly because of their scarcity of

17 cultivation and used only in holistic purpose. Some of the wild species of bananas like Ensete glaucum, Musa magnesium, Musa cheesmanii, Musa balbisiana, Musa laterita, etc. have been recorded from the Manipur state in India. Bandyopadhyay, (2013) reported India with rich biodiversity of banana is the largest producer . But, India is absent in the world trade which is estimated at 14 million tons worth $4.7 billion a year. The contribution of banana to GDP of agriculture in India is 2.8%. Year wise area, production and productivity of banana in India are presented (Table. 3.4.2). In India the productivity of banana in the year 2012-13 was 34.2MT/ha whereas productivity of banana is maximum in state of Tamil Nadu (19.4%), followed by Gujarat (17.1%) . The other foremost banana producing states from India are as follows:

Maharashtra (13.6%), Andhra Pradesh (12.2%), Karnataka (9.5%), Bihar (6.4%), Madhya Pradesh (6.4%), West Bengal (4.1%) Assam (3.2%), Odissa (2.0%), and other states (6.2%). In the Maharashtra major banana producing districts are Jalgaon, Nanded and Parbhani (National Horticulture Board and Ministry of Agriculture, Govt. of India, 2013). Table. 3.4.2. Yearwise Area wise production and productivity of banana in India

Year Area Total Production Total Productivity (in Frt. (in '000 MT) Frt. production (in MT/ha) '000 area (%) ha) (%) 1991-92 383.9 13.4 7790.0 27.2 20.3 2001-02 466.2 11.6 14209.9 33.0 30.5 2002-03 475.3 12.5 13304.4 29.4 28.0 2003-04 498.6 10.7 13856.6 30.4 27.8 2004-05 589.6 11.9 16744.5 34.0 28.4 2005-06 569.5 10.7 18887.8 34.1 33.2 2006-07 604.0 10.9 20998.0 35.3 34.8 2007-08 658.0 11.2 23823.0 36.3 36.2 2008-09 709.0 11.6 26217.0 38.3 37.0 2009-10 770.3 12.2 26469.5 37.0 34.4 2010-11 830.0 13.0 29780.0 39.8 35.9 2011-12 796.5 11.9 28455.1 37.2 35.7 2012-13 776.0 11.1 26509.1 32.6 34.2 2013-14 802.6 11.1 29724.6 33.4 37.0

(Source: Director of Horticulture / Department of Agriculture & Cooperation 2013-14)

18

While statewise Area, Production and Productivity of Banana in India given in following (Table. 3.4.3). Table. 3.4.3. Statewise area, production and productivity of banana in India. Area in ‘000HA, Production in ‘000MT and Productivity – MT/HA State 2010-11 2011-12 2012-13 2013-14 Ar Prod PD Ar Product PD Are Product PD Area Prod PDY ea uctio Y ea ion Y a ion Y uctio n n Tamilnadu 125 8253. 65. 130 6736.4 51. 111. 5136.20 46. 118.0 5650. 47.9 .4 0 8 .4 7 36 1 4 00 Gujarat 64. 3978. 61. 65. 4047.8 62. 70.5 4523.49 64. 66.50 4225. 63.5 7 0 5 0 3 8 1 49 Maharashtra 82. 4303. 52. 82. 4315.0 52. 82.0 3600.00 43. 83.00 4830. 58.2 0 0 5 0 6 0 9 60 Andhra 79. 2774. 35. 82. 2899.6 35. 92.6 3242.80 35. 90.48 3166. 35.0 Pradesh 3 8 0 0 0 5 0 90 Karnataka 111 2281. 20. 91. 2351.5 25. 97.4 2529.60 26. 102.7 2675. 26.1 .8 6 4 6 7 0 0 1 63 Bihar 31. 1517. 47. 32. 1580.5 49. 33.0 1702.41 51. 34.31 1435. 41.8 9 1 6 1 2 6 5 78 Madhya 38. 1719. 45. 24. 1379.2 55. 25.7 1701.00 66. 26.27 1735. 66.0 Pradesh 1 6 2 8 6 6 0 00 Wesh 42. 1010. 24. 43. 1054.0 24. 44.7 1077.80 24. 45.50 1097. 24.1 Bengal 0 1 0 7 1 0 1 50 Assam 47. 723.6 15. 49. 745.3 15. 51.5 837.02. 16. 50.81 857.7 16.9 6 2 1 2 1 2 2 Odissa 26. 488.7 18. 27. 506.2 18. 27.4 521.31 19. 25.06 476.6 19.0 9 2 5 4 9 0 0 Others 180 2730. 15. 167 2839.5 17. 139. 1637.47 11. 159.8 3573. 22.3 .9 5 1 .5 0 49 7 9 33 (Source: Indian Horticulture Database, 2013/All India 2013-14 (Final Estimates), Department of Agriculture & Cooperation) The banana production-Maharashtra Scenario: (Table: 3.4.4)

19

Table. 3.4.4. District wise (major) scenario of banana production in Maharashtra

Sr. Name of Area (ha) Production (MT) No District . 1 Jalgaon 62752.41 5110196.14 2 Amravati 680.95 109445.14 3 Pune 948.26 625.62 4 Sindhudurg 191.36 789.10 5 Akola 600 30000 6 Buldhana 700 42000 7 Aurangabad 74.128 4077.04 8 Parbhani 3200 160000 9 Nanded 14000 8,40,000

In the Maharashtra Jalgaon district has the maximum hectares under this crop (Over 60,000 ha). Maharashtra stands first in the country with a production over 40 percent of the banana production of our country. The area under banana cultivation is 62 thousand hectares in Maharashtra. The banana is commercially cultivated in Thane district of Konkan, which is mainly concentrated in Vasai and `Palghar’ tehsils. The main banana varieties cultivated in the Maharashtra state are - Dwarf Cavendish, Grand Nain, Ardhapuri, Nendran, Basrai, Robusta, Lal Velchi and Safed Velchi. 3.5. Banana Plant- Sigatoka disease, causes and control: The Sigatoka disease of banana involves the complex of three associated ascomycetous Fungi such as Mycosphaerella musicola, Mycosphaerella fijiensis, and Mycosphaerella eumusae. The accurate distribution of these three species and their disease epidemiology remain unclear, because their life cycles and symptoms are quite similar reported by Arzanlou et al., 2007. Three species of Mycosphaerella are known to cause Sigatoka leaf diseases on banana leaves. The Mycosphaerella musicola causes yellow Sigatoka, Mycosphaerella fijiensis causes black Sigatoka and Mycosphaerella eumusae causes leaf spot on banana. The major disease of banana plant is yellow Sigatoka disease and was reported in Fiji in 1913 (Massee, 1914). The causative agent of Yellow Sigatoka disease which is ascomycete mold Mycosphaerella musicola (Pseudocercospora musae) was initially described as a pathogen of banana plant in Java in 1902 (Zimmerman, 1902).The causative agent of yellow Sigatoka is Mycosphaerella musicola which is the polycyclic pathogen that constantly produces its reproductive structures because of

20 their reproductive strategy. The disease development curve in a susceptible host may show exponential growth within a given time interval, provided that the environmental conditions are favorable. These environmental variables also influence the aerobiology of the fungal pathogen and the epidemiology of the Sigatoka disease. An understanding of the disease progression, so as to exactly identify the time required for the disease to reach its exponential phase, or maximum intensity, important to aid in the choice of control strategies and to verify their effects on banana plant (Rocha et al., 2012). There are two different types of conidia/spores are involved in the propagation of yellow Sigatoka, namely, conidia and ascospores present on conidiospore (Cordeiro, 1997)

a) Life cycle of Mycosphaerella musicola (www.slideshare.net)

21

b) M. musicola sporodochia with conidia c) M. musicola sporodochia without conidia (Henderson and Grice, 2008)

The conidia (asexual spores) are generally produced continuously in environments in high level of humidity. They are disseminated by the washing of the leaf surface by rain, which explains the severe infections occasionally occurred in the tiller under more mature banana plants. However, ascospores (sexual spores) produced at the same lesions from which conidia were released earlier, appear later and are compulsorily ejected from pseudothecia also owing to high comparative humidity and even in dry climates but due to greater periods of leaf wetness (Simmonds, 1966). The thickness of conidia in the air is related to the concentration of yellow Sigatoka, the decrease in the incubation periods and symptom creation always connected with changeable temperature and humidity level (Guyot and Cuille, 1958).The teleomorph and anamorph of this heterothallic and haploid fungus may be present on infected banana leaves. The long distance spread of the disease between plantations within a region has been attributed to airborne ascospores, while disease spread within plantations is caused by splash dispersal of mass-produced conidia of Mycosphaerella musicola (Meredith, 1970). Blomme et al., 2011 stated that the impact of diseases and pests, especially Sigatoka leaf spots disease has been recognized as a serious constraint to banana (Musa spp.) production in different parts of the world. The yellow sigatoka is a polycyclic disease and their reproductive structures are produced and disseminated continuously and may result in numerous disease cycles yearly (Zapater et al., 2008). Annual average of lesions development on banana leaves of yellow sigatoka caused by

22

Mycosphaerella musicola were calculated at 14 days intervals for 57 banana sites in North Queensland production region located in the wet tropics between Cardwell and Innisfail reported by Gerald et al ., (2003). Milgroom, 1995 proposed that populations shown to be very much differentiated due to limited gene flow and genetic float could hypothetically be managed separately. The identification of different area wise populations of Mycosphaerella musicola mold can be used to describe disease management units, and their importance may need to be implemented if diverse populations of Mycosphaerella musicola found in different regions in the world. The pattern of spread of Mycosphaerella musicola around the world has been well-documented (Mourichon & Fullerton, 1990) and spreading mechanisms for this pathogen on a regional scale are well understood. The Mycosphaerella musicola attacks almost all the commercially cultivated banana varieties in the India and the a large amount of harshly infected banana cultivars includes Rasthali, Poovan, Karpooravalli, Red banana, Robusta and Cavendish group while The Nendran is comparatively tolerant to this fungus (Chandra, 1991). The yellow Sigatoka disease was confined to the Australasia-Pacific region until 1933, when disease outbreaks were documented in different locations in Latin America, Africa, and Asia. A hypothesis explaining the pattern and mechanisms for the universal distribution of Mycosphaerella musicola was formulated by Stover, 1962 based on their record of detection. The yellow Sigatoka disease spread from Java, Indonesia to Fiji was attributed to the movement of contaminated leaves of the banana with uses of the packing material for transport of inter-island in this area. The extensive distance spreading from Fiji to Australia was proposed to have occurred by airborne spores produced by Sigatoka disease in Fiji. In the Australia, it was hypothesized that a huge number of airborne ascospores were carried westwards with the help of wind currents to eastern Africa and the Caribbean to start near- simultaneous infection outbreaks in these regions by Mycosphaerella musicola fungus. Stover, (1962) reported the strength of worldwide disease dispersal theory has not been examined and lacks its exact analysis. The number of conditions must be content for epidemics of this disease to develop after long distance spreading such as feasible inoculum, the presence of susceptible banana plants as a host where the spores to be landed and the most favorable environmental surroundings for germination, infection and reproduction by the Sigatoka disease pathogen. The Mycosphaerella musicola isolates were examined into four geographic populations

23 groups representing Latin America, Africa, Caribbean, Indonesia and Australia (Hayden et al., 2003). The Yellow Sigatoka caused the primary biotic problem for the Brazilian banana crop with high pathogenic variability among the isolates of Mycosphaerella musicola (Aparecida et al., 2014). The Yellow Sigatoka, which is caused by Mycosphaerella musicola or Pseudocercospora musae facing a great trouble in Brazil for the production of banana because of its high variation in pathogenic condition (Cordeiro and Matos, 2005). In India the Sigatoka disease is more widespread in the states like Tamil Nadu, Kerala, Maharashtra (Jalgaon district), Karnataka, Gujarat, Andhra Pradesh, West Bengal, Tripura and Uttar Pradesh where the highest disease severity (90-100%) was observed in cultivars such as Poovan (Mysore-AAB), Cavendish group (Grand Nain, Robusta, Mahalakshmi and Srimanthi), Hill banana (AAB), Nendran (AAB), Pachanadan (AAB), Monthan (ABB) etc. The disease is found mostly in the winter and rainy period, which coincides with superior vegetative and shooting stages of the crop. The improvement of necrotic patches on the leaves of banana plant resulted defoliation occurs and then delayed in the flowering, reduction in number of fingers and hands, untimely ripening of the banana fingers and peel splitting in the fruits will be occurred. The investigation conducted in Jalgaon district of Maharashtra in 2011 where the banana was grown in about 40,000 ha indicated that there were only 2-6 green leaves in most of the banana farm and in some farms there was completely absence of green leaf in the time of bunch maturing phase of banana (Ganga and Thangavelu, 2014). Noorulla et al., 2013 reported that the survey conducted in the seven major banana growing districts from Karnataka state in India implied occurrence of yellow disease in all banana growing areas. The yellow Sigatoka leaf spot caused by Mycosphaerella musicola is considered as one of the important diseases of banana in India. The economic losses owing to the disease have been very serious in some areas that banana production has ceased altogether, particularly where susceptible varieties were cultivated. A severe prevalence of Sigatoka was recorded in banana orchards of South Gujarat during 1976 to 1982 causing drying and defoliation of leaves and premature ripening of fruits in bunches on banana plants. In the state of Karnataka especially in northern Karnataka Sigatoka leaf spot is generally measured as serious belt of banana disease. For the control of Sigatoka leaf spot disease the two sprays used commonly viz. 0.05% propiconazole (very effective) and 0.1% carbendazim.

24

3.6. Banana plant associated N2 fixing bacterial endophytes: There are several definitions of endophytes such as microorganisms living within plant tissues for all or part of their life cycle without causing any visible symptoms of their presence reported by Wilson, 1993. Long et al., (2008) suggested that the endophytes are diverse microorganisms inhabiting in internal tissues of the plants which are defined as ‘microbes that colonize living, internal tissues of plants without causing any immediate, overt negative effects’. The presence of bacteria resident within the tissues of healthy plants was first reported as early as 1926 (Hallmann et al., 1997). The function of endophytic bacteria to fix nitrogen and promote plant growth has renewed the interest in such relations with plant and endophytes. The endophytic non-rhizobial diazotrophs like Gluconacetobacter spp, Azoarcus spp., and Herbaspirillum spp. have been isolated from kallar grass, rice and sugarcane respectively (Cocking, 2003). It is reported by Muthukumarasamy et al., 2002 that the nitrogen fixing endophytic bacteria like Gluconacetobacter diazotrophicus was found to be associated with banana, sugar cane, pineapple, sweet potato, mango, Cameroon grass and other plants. The endophytic bacteria (Agrobacterium, Aneurinibacillus, Bacillus, Enterobacter, Klebsiella, Lysinibacillus, Micrococcus, Paenibacillus, Rhizobium and Sporolactobacillus) were isolated from banana ‘Prata Ana’ roots (Souza et al., 2013). The diversity of endophytic bacteria from asymptomatic banana was different from that of Symptomatic plants (Hadiwiyono et al., 2013). Ngamau et al., 2012 reported species of Raoultella, Rahnella, Yokenella, Yersinia, Ewingella, Pseudomonas, Klebsiella Serratia and Bacillus known as nitrogen fixing microorganisms. The discovery of eight new nitrogen fixing bacteria, in addition to Herbaspirillum seropedicae, Burkholderia brasilensis, Herbaspirillum rubrisubalbicans, and Blomia tropicalis with bacterial isolates from banana and pineapple revealed the great diversity of nitrogen fixing bacteria related with these two fruit crops (Pedrosa et al., 2011). Mohanta et al., 2010 reported that endophytes promote plant growth, yield, suppress pathogens, solubilize phosphate and supply assimilable nitrogen to the plants. There are few reports of endophytes found in banana such as Bacillus and Pseudomonas spp were reported by Harish et al., 2008. The genera of larger incidence in diverse species from bananas are: Burkholderia, Pseudomonas and Enterobacter (Thomas et al., 2008).

25

Ting et al., 2008 reported Serratia spp from banana plant as good endophytes. Endophytes were discovered in Germany by Freeman in 1904 and identified an endophytic fungus in Persian darnel (annual grass). Some grasses with high endophyte content in the plant were often resistant to the attack by certain harmful insects. The actinobacterial endophyte with N-fixer Frankia that formed actinorhizae with 8 families of angiosperms .The endophytic bacteria promote plant growth and yield as well as suppress pathogens, solubilize phosphate and contribute assimilable nitrogen to the plants in Indian environment is reported by Rosenblueth et al., 2006. But there is no information available on their diversity as well as functional potentiality with regards to growth and nutrition in banana. In addition to possible supply of nutrients to banana plant some endophytes can work as biocontrol agents in banana e.g. Cao et al., 2004 reported isolation of endophytic actinomycetes from leaves and roots of banana (Musa acuminata) plants and their antimicrobial properties against Fusarium oxysporum sp. with positive significance. Martinez et al., 2003 reported Citrobacter, Enterobacter, Klebsiella and Rhizobium spp which have good nitrogen fixing efficiency. Subsequently they reported the patterns and sequences of 16S rRNA genes that allowed the identification of banana isolates as Herbaspirillum, Burkholderia and Ochrobactrum-related bacteria (Cruz et al., 2001). With the help of morphological and physiological characterization, bacteria similar to Herbaspirillum were identified from non-sterilized banana tissues that were different from species of Herbaspirillum isolated from gramineous plants as well as other banana diazotrophs not corresponding to Herbaspirillum were also encountered but their taxonomic association was not defined (Weber et al., 2001). Bacon and White, (2000) and Weber et al., (2000) reported that the micropropagated banana plants grew faster upon inoculation of Herbaspirillum and Burkholderia cepacia related endophytic bacteria. Weber et al., 1999 reported Azospirillum brasilense and Azospirillum amazonese from banana. They also reported Burkholderia spp. (1999) and Herbaspirillum spp. (2001) are banana plant endophytes. The Fusarium fungal endophytes from banana roots is reported by Niere et al., 1999 as possible biocontrol agent against Radopholus similis, a burrowing nematode and one of the major pathogens affecting banana production worldwide and causing banana root rot. Several diazotrophic endophytes, such as the plant-associated Azoarcus species, Acetobacter diazotrophicus or Herbaspirillum seropedicae, appear to be tightly associated with plant-associated fungi or plants (Hurek et al., 1997b). The PGPR

26 injection in bananas showed a significant amount of nitrogen fixation (Mia et al.,

2007) and N2 fixing bacteria were isolated from pineapple and banana (Musa spp.). Bacteria within the genera Agrobacterium and Rhizobium have the unique capacity nitrogen fixation in root nodules, to induce prolific root formation and autonomous crown-gall tumors on several higher plants including most of dicots, some gymnosperms and some monocots (Matthysse, 2006). Recently Dobereiner et al., 1993 suggested that the term "endophytic diazotroph" be used for microaerobically nitrogen fixing bacteria like Herbaspirillum spp. and Acetobacter diazotrophicus were isolated from seeds of rice, roots, stems, and leaves of sugarcane. The most predominant and studied endophytes belong to three major phyla (Firmicutes, Actinobacteria and Proteobacteria) and include members of Azoarcus (Krause et al., 2006), Acetobacter (renamed as Gluconobacter) (Bertalan et al., 2009), Bacillus (Deng et al., 2011), Enterobacter (Taghavi et al., 2010), Burkholderia (Weilharter et al., 2011), Serratia (Taghavi et al., 2009), Herbaspirillum (Pedrosa et al. 2011), Pseudomonas (Taghavi et al., 2009), Streptomyces (Suzuki et al., 2005) and Stenotrophomonas (Ryan et al., 2009). The biological atmospheric dinitrogen fixation by its protonation and reduction to ammonia is achieved in diazotrophic bacteria by the nitrogenase enzyme complex. Phytohormones play an important role in the signaling and regulating of plants growth and development. The phytohormonal substances such as auxins and gibberellins by different PGPB have been proposed as one of the mechanisms, besides N2 fixation, to explain plant growth promotion (Pedraza, 2008). Rothballer et al., 2008 reported in recent years, the application of endophytic bacterial bioinoculants supplying N requirement efficiently to the different host plants including cereal crops have drawn attention for increasing plant yield in sustainable mode. Additionally, some of the rhizobial isolates have also been found to colonize non-legume plant as an endophyte and benefit to their host. In the conditions of benefiting through nitrogen fixation, endophytic bacteria are considered to be better than that of rhizospheric one as they provide fixed nitrogen directly to their host plant and fix nitrogen more efficiently due to lower oxygen pressure in the inner part of plants than that of soil. The endophytic bacteria resides in the endosphere, the internal microenvironment of root, shoot and leaves and hence, these bacteria might interrelate more closely with the host plant and therefore, could be efficient biological control

27 agent in sustainable crop production and offer sole opportunity for crop protection and biological control (Melnick et al., 2008).

3.7. Antimicrobial potential of N2 fixing and PGP producing bacterial endophytes from banana: The biocontrol rhizobacteria that protect plants and crops from pathogens via promoting plant resistance or as an antimicrobial agents (Manivasagan et al., 2013). Some endophytes protect their hosts from infectious agents and adverse conditions by secretion of bioactive secondary metabolites (Strobel, 2002). The use of biological control agents as an alternative to fungicides is increasing rapidly in the present day agriculture due to the harmful effects of chemical pesticides. The members of genus Trichoderma and Pseudomonas have extensive been known for their potential to reduce the plant disease caused by fungal plant pathogens and they have gained significant importance as potential antagonistic microorganisms (Pant and Mukhopadhyay, 2001). Numerous reports have shown that endophytic microorganisms have capacity to control plant pathogens, insects and nematodes (Staniek et al., 2008). Antagonistic activity (Muthukumarasamy et al., 2000) and disease resistance induction (Arencibia et al., 2006) by Gluconacetobacter diazotrophicus endophyte have been unveiled. The Yellow Sigatoka disease Caused by Mycosphaerella musicola fungus is recognized and aggressively controlled in Australia with the help of intensive amount of fungicide treatments and removal of diseased banana leaves (Henderson et al., 2006). The control plant pathogens by biological method with antagonistic microorganisms is a non harmful method apart from chemical fertilizers (Harman, 1991) and is known to be a low-priced and effective eco-friendly method for the management of crop diseases (Cook and Baker, 1983). Among these the bacterial antagonists properties have the double advantage of quicker multiplication and higher rhizosphere capability hence, the Pseudomonas fluorescens have been successfully used for biological control of several harmful plant pathogens (Ramamoorthy et al., 2002) and also biological control of plant diseases by using PGPR strains mainly from the genus of Pseudomonas is an effective replacement for very costly chemical pesticides to suppress several plant diseases (Compant et al., 2005). Two strains of Serratia marcescens were also reported on controlling black Sigatoka disease of bananas in field level with the identical effectiveness as eco-friendly and conventional fungicides (Gonzalez et al., 1996). Vawdrey et al. (2004) evaluated the effectiveness of five mineral as well as four plant

28 oil and a plant derived marker on suppressing yellow Sigatoka of bananas. The most of the fungicides are useful to control of spots and very dangerous anthracnose diseases of banana plant. Several types of effective fungicides have been used for suppressing the banana diseases from which triazoles is an important one (Romero and Sutton, 1997). For many years, breeding for Sigatoka resistance has been considered as an important strategy to control this disease. Harelimana et al., 1997 used the toxins produced by M. fijiensis fungus for the screening of banana cultivars resistant to yellow Sigatoka of bananas. Jimenez et al., (1987) reported Pseudomonas sp. as a biocontrol agent against black Sigatoka of bananas. The mixtures of plant growth promoting and endophytic bacteria including Bacillus spp. used against bunchy top virus of banana with superior result has been reported (Harish et al., 2009). The plant growth promoting rhizobacteria have recently been shown to induce complete resistance against disease causing fungi, bacteria and viruses as well as to improve growth of plants. The application of arbuscular mycorrhizal fungi and PGPR together which have highly benefits to banana plants as well as the adaptation stage of micropropagated banana (Rodriguez Romero et al., 2005). The inoculums Mycorrhiza are the biofertilizer that is increasingly being utilized and accepted in agriculture industry of Malaysia. The big scale productions of biofertilizers are produced mainly for supplying nutrient, amelioration of toxic effect in soils, root pest and disease control, enhanced water usage and soil fertility (Abdul, 2009). The G. diazotrophicus and sugarcane relationship represents a model system for monocot–diazotrophic association and even though their interactions have not been entirely understood, different reports indicate that G. diazotrophicus is able to promote plant growth with the help of phytohormones production and also contributes nitrogen fixation. It was also observed that this bacterium has the capability to solubilize Zn and P compounds as well as to produce a bacteriocin that inhibits the growth of Xanthomonas albilineas causal agent of leaf scald disease in sugarcane (Pinon et al., 2002). The many endophytic bacteria possess a number of plant beneficial traits in vitro; few of those exhibit them in plants and only a few numbers of endophytes proved to be very effective plant growth promoting and/or biocontrol agents under farming conditions (Scherwinski et al., 2008; Berg, 2009). The plant diseases are responsible for yearly crop losses at a total value of more than 200 billion Euros (Agrios, 2005).

29

The considerable disease suppression was also reported for plants of wheat endophytically colonized with B. subtilis bacteria (Liu et al., 2009) and for banana plants pre-inoculated with endophytic Burkholderia and Pseudomonas (Fishal et al., 2010). The one third of rhizosphere bacteria produce AFMs and therefore may play an important role in the control of diseases caused by pathogenic fungi (Opelt et al., 2007).

3.8. N2 fixation and PGP production potential of N2 fixing bacterial endophytes from banana: The endophytic microorganisms have been reported from a variety of plants. In the study of banana, the somatic embryogenic cultures of banana (Musa accuminata - AAA) were found to have association with endophytic bacteria which were present initially in a covert state. The presence of bacteria was detected only in suspension cultures derived from the somatic embryogenic cultures of banana. The endophytic bacteria isolated from embryogenic cell suspension culture were identified as Bacillus sp and Ralstonia sp. The Ralstonia sp. showed the presence of various plant growth promoting potential including the production of indole acetic acid and siderophore ( Jimtha et al., 2014). In the current times, there has been a reversed interest in the search of plant growth promoting rhizobacteria (PGPR) for sustainable production of crops (Meera and Balabaskar, 2012). The microorganisms have very important role in agriculture in order to support in the exchange of plant nutrients and decrease application of harmful chemical fertilizers as much as possible. The plant Growth Promoting Rhizobacteria (PGPR) is able to exert a positive effect on leading plant growth (Noori and Saud, 2012). Nitrogen is a necessary plant nutrient, widely applied as N-fertilizer to improve yield of agriculturally essential crops. An interesting alternative to avoid or reduce the use of chemical N-fertilizers could be the utilization of plant growth promoting bacteria (PGPB) to enhancement of plant growth and yield of many plant species as well as several of agronomic and ecological importance. The PGPB belong to genera, including Azotobacter, Azospirillum, Herbaspirillum, Burkholderia, Gluconacetobacter, Rhizobium, Bacillus, Pseudomonas, and other endophytic bacteria. They are capable of promoting plant growth through different mechanisms including the biological nitrogen fixation, the enzymatic reduction of the atmospheric dinitrogen (N2) to ammonia, catalyzed by nitrogenase enzyme (Pedraza, 2008).

30

The number of nitrogen fixing bacteria including Azospirillum lipoferum, Azospirillum brasilense, Azospirillum halopraeferens, Azoarcus indigens, Azoarcus communis, Azovibrio restrictus, Azospira oryzae and Burkholderia tropica reported by (Peng et al., 2006). Bandara et al., 2006 reviewed that endophytic bacteria supply essential vitamins to plants. The production of auxin-like compounds increases seed production and germination along with increased shoot growth and tillering. Some endophyte infected on the host plant includes, osmotic adjustment, stomatal regulation, modification of root morphology, enhanced uptake of minerals and alteration of nitrogen accumulation and metabolism. The endophytic bacteria such as Azoarcus spp. have interesting features with respect to plant- microbe interactions (Engelhard et al., 2000). It has been also documented that bacteria occur in the internal tissues of healthy plants: endophytic bacteria have been described as spending most of their life cycle within the plant without causing symptoms of plant damage (Hurek and Hurek, 1998a). Several gramineous plants have been shown to be associated with endophytic nitrogen fixing bacteria such as Herbaspirillum seropedicae and Acetobacter diazotrophicus (James et al., 1994; James and Olivares, 1998) and Azoarcus spp. (Hurek and Hurek, 1998b). A potential use of diazotrophic endophytes for plant growth promotion, antagonistic effects or biological nitrogen fixation for a more sustainable agriculture has stimulated interest in studying these bacteria (Boddey, 1995; Triplett, 1996; Hurek and Hurek, 1998a). Diazotrophs that efficiently colonize the rice interior might have the potential to fix nitrogen (Hurek et al., 1997a). The PGPR species, Azospirillum was suggested to secrete gibberellins, ethylene and auxins (Perrig et al., 2007). The nitrogen fixation was the primary mechanism proposed to explain improved plant growth next to inoculation with Plant Growth Promoters. This was mainly because of an increase in number of nitrogenous compound and nitrogenase activity in inoculated plants (Bashan & Holguin, 1997). A significant positive effect on grain yield and nitrogenase activity in roots of barley was obtained due to combined inoculation of nitrogen fixer’s like Azospirillum lipoferum, Arthrobacter mysorens with phosphate solubilizing strain Agrobacterium radiobacter by Belimov et al., 1995. Nitrogen is an important plant nutrient in the agriculture field to fertilization with nitrogen products which widely and increasingly practiced to increase the production yield of food (Hurek and Hurek, 2003).

31

The PGPB are defined as free-living soil, rhizosphere, rhizoplane, endophytic and phylosphere bacteria that under certain conditions with beneficial for plants (Bashan and de-Bashan, 2005). They have capacity to promote growth of plants through different mechanisms, such as biological nitrogen fixation (BNF), phytohormone production, phosphate solubilization and siderophore production. The Indole acetic acid (IAA) is a naturally occurring auxin with broad physiological effects on plant. It can be implicated in plant pathogenesis or stimulates plant growth (Patten and Glick, 1996).The Indole acetic acid (IAA) is one of the most physiologically active auxins. IAA is a common product of L- tryptophan metabolism produced by several microorganisms including Plant Growth Promoting Rhizobacteria (Lynch, 1985) 3.9. Koch postulate studies with banana pathogen: The Koch’s postulates for the pathogenicity of M. theobromae (Turconi) Zare & W. Gams in which the pathogen caused banana cigar end rot disease reported by Masudi and Bonjar, 2012. Life has changed Since the 1880s when Robert Koch elucidated his guidelines, later to be called Koch’s Postulates for determining whether a microorganism is the cause of a disease reported By Fredricks and Relman, (1996). The original isolations of fungus were made on Potato Dextrose Agar medium by surface sterilization and plating the infected tissues or the lesions of plant. Single spore isolations were obtained and tested for their pathogenicity on healthy seedlings by following Koch’s Postulates. To fulfill Koch’s Postulates the samples of experimentally infected seedlings were removed and assayed to verify the incidence of the causal agent. The re-isolated fungus was cultured on Potato Dextrose Agar medium and cultural and morphological characteristics were recorded and compared to the original isolate. Typical disease symptoms on hypocotyls were initiated by third day after inoculation of the seedlings (Reddy and Faeth, 2010). In 1884 Robert Koch and Friedrich Loeffler formulated the four postulates that gave the theoretical and practical bases on which to establish a causal relationship between a microbe and a disease (Koch, 1884). In the study of were to firstly identify the pathogens associated with the leaf spot diseases on the two respective hosts and secondly to establish pathogenicity, thereby confirming Koch’s postulates (Koike et al., 2011). 3.10. Bioinoculant development using banana endophytes: The biofertilizers keep the soil environment rich in all kinds of micro and macronutrients via nitrogen fixation, potassium and phosphate solubilization or mineralization, release of plant growth regulating substances, production of

32 antibiotics and biodegradation of organic matter in the soil (Sinha et al., 2014). The environmental stresses are becoming a major problem and productivity is declining at an unprecedented rate. Our dependence on chemical fertilizers and pesticides has encouraged the thriving of industries that are producing life-threatening chemicals and which are not only hazardous for human consumption but can also disturb the ecological balance. Biofertilizers can support to solve the problem of feeding an increasing global population at a time when agriculture is facing various environmental stresses. It is important to realise the useful aspects of biofertilizers and implement its application to modern agricultural practices (Bhardwaj et al., 2014). The additional advantages of biofertilizers include longer shelf life causing no adverse effects to ecosystem. Diverse species of the genus Azospirillum including Azospirillum lipoferum, Azospirillum brasilense, Azospirillum amazonense, Azospirillum halopraeferens and Azospirillum irakense have been reported to improve productivity of various crops (Sahoo et al., 2014). The chemical fertilizers are industrially manipulated substances composed of known quantities of nitrogen, phosphorus and potassium, and their exploitation causes air and ground water pollution by eutrophication of water bodies (Youssef et al., 2014). A major focus in the coming decades would be on safe and eco-friendly methods by exploiting the beneficial microorganisms in sustainable crop production (Nina et al., 2014). Biofertilizer is a relatively safer, environmentally friendly and cost-effective approach as an alternative to reduce use of chemical fertilizers (Tan et al., 2014). The biofertilizers are from biological wastes and they are not hazardous to soil. They are very useful in that they help in enriching the soil with the beneficial microorganisms and these microorganisms produce useful organic nutrients for soil and help in fighting to plant pathogens. Besides accessing nutrients, for current intake as well as residual, different biofertilizers also provide growth promoting factors to plants and some have been successfully facilitating composting and effective recycling of solid wastes. Biofertilizers, depending on available or presence of effective microorganisms have come up as a replacement for chemical fertilizers to improve soil fertility and crop yield in sustainable agriculture. Symbiotic, free-living soil bacteria are named as plant growth promoting rhizobacteria (PGPR). They are included in important ecosystem developments and their activities includes in biological control of plant pathogens, nitrogen fixation, mineralization of nutrients and phytohormones production because

33 of these qualities, they occupy a unique place in the sustainability of agroecosystems (Tunde et al., 2014). The biofertilizers are a supplementary constituent to soil and crop management traditions viz., crop rotation, organic adjustments, tillage maintenance, recycling of crop residue, soil fertility renovation as well as the biocontrol of pathogens and insect pests which operation can significantly be useful in maintaining the sustainability of various crop productions (Sahoo et al ., 2013). The Azospirillum was shown to exert beneficial effects on plant growth and crop yields both in greenhouse and in field trials (Saikia et al., 2013). Biofertilizer help in increasing crop productivity with the help of biological nitrogen fixation, increased availability or uptake of nutrients through solubilization or increased absorption stimulation of plant growth through hormonal action or antibiosis, or by decomposition of organic residues. Additionally, biofertilizer as to replace use of hazardous chemical fertilizers reduces amount and cost of chemical fertilizers and thus prevents the environment pollution from extensive use of chemical fertilizers. The application of the biological and organic fertilizers, a low input system can be carried out, and it can be helped achieving sustainability of farms (Mohammadi and Sohrab, 2012). The endophytic bacteria of bananas in Kenya were isolated and identified as Serratia, Pseudomonas, Rahnella, Enterobacter, Yokenella, Raoultella, Klebsiella, Yersinia, Ewingella and Bacillus species. R. aquatilis and F. oryzihabitans were the most efficient in phosphate solubilization and siderophore production respectively as well as they also showed ability to fix free nitrogen which proposed as potential biofertilizers in banana production. The greenhouse and field investigations are however suggested for confirmation of this potentiality (Ngamau et al., 2012). When biofertilizers are applied as seed or soil inoculants, they multiply and participate in nutrient cycling and benefit crop productivity and the agriculturally useful microbial populations cover plant growth promoting rhizobacteria, N2 fixing cyanobacteria, mycorrhiza, plant disease suppressive beneficial bacteria, stress tolerance endophytes and biodegrading microbes (Singh et al., 2011). The plant growth promoting rhizobacteria (PGPR), such as nitrogen fixing microorganisms have been used as biofertilizer to stimulate growth of plant (Mia et al., 2010). Boraste et al., 2009 has reported that biofertilizers are low price, effective and renewable source of plant nutrients to supplement chemical fertilizers. In general, 60% to 90% of the total applied fertilizer is lost and the remaining 10% to 40% is taken up by plants in agriculture. In this regard,

34 microbial inoculants have paramount importance in integrated nutrient management systems to sustain agricultural productivity and unpolluted healthy environment (Adesemoye and Kloepper, 2009). The PGPR or co-inoculants of PGPR and AMF can advance the nutrient use efficiency of fertilizers. A synergistic interaction of PGPR was better suited to 70% fertilizer plus AMF and PGPR for P uptake. Similar trend were also reflected in N uptake on a whole tissue basis which shows that 75%, 80%, or 90% fertilizer plus inoculants were significantly comparable to 100% fertilizer (Adesemoye et al., 2009). The effect of the combined inoculation of the arbuscular mycorrhizal fungus Glomus manihotis and a rhizobacteria consortium of Bacillus spp. on micropropagated banana plantlets, during the acclimatization phase under routine nursery conditions was investigated by Romero et al., (2005). The inoculation in banana nursery showed better growth and seedling health and consequently increased the seedling survival rates (Guerra, et al., 2005). The inoculation of rhizobacteria viz. Azotobacter cryoococcum, Pseudomonas fluorescens and Azospirillum brasilense alone and in combination with root symbionts, Rhizobium sp. and Glomus mossae improved plant growth and reduced gall disease formation on chick pea (Cicer arietinum) (Siddiqui & Mahmood, 2001). Biofertilizers as microbial inoculants that can promote plant growth and productivity is internationally accepted as an alternative source of N- fertilizer. It is environmental friendly and can be used to ensure a sustainable banana production. In this biofertilizer technology new systems are being developed to increase the biological N2 fixation (BNF) with cereals and other non-legumes by establishing N2-fixing bacteria within the roots (Cocking, 2000). Shamsuddin et al. (1999) found increased amounts of P and K uptake in banana plants inoculated with PGPR. Inoculation of A. brasilense increased the dry weight, plant height, P absorption and lipid content in oil seed (Bashan et al., 2000). Nitrogen fixation and plant growth promotion by plant growth promoting bacteria are important criteria for an effective biofertilizer. The inoculation of associative and free living N2-fixing bacteria have been shown to produce beneficial effects on plant growth, thus they are termed plant growth promoting rhizobacteria (Kloepper et al., 1980; Bashan & Holguin, 1998). It was found by Glick et al. (1998) that PGPR could enhance the growth of plant by suppressing the expression of ethylene. The increased use of chemical fertilizer is undesirable, however because:

35

(1) Its production is an energetically costly process and most of the energy is provided by the consumption of non-renewable fossil fuels and (2) Considerable pollution is caused through both the production and use of mineral N-fertilizers and this is exacerbated by the relatively low efficiency of their uptake by the plants due to nonextensive root system (Ladha & Reddy, 1995; Ladha et al., 1997). PGPR inoculation increased the stomatal conductance and lowered the proline concentration in leaves of banana seedling grown under submerged condition. It also alleviated plant stress due to submergence, while leaf growth and chlorophyll content and new root formation were lowered under submerged condition (Shamsuddin et al., 2000). The mixed inoculation of Vicia faba L. with four different PGPR strains changed the total accumulation, concentration and/or distribution of the macro-and micronutrients (Rodelas et al., 1999). The combined application of Azospirillum, Azotobacter and inorganic nitrogen fertilizer resulted in taller plants, number of leaves and girth, but could not show yield improvement and root development in bananas compared to un-inoculated control (Wange & Patil, 1994). Combined inoculation of A. brasilense and the phosphate-solubilizing bacteria, Pseudomonas strica or Bacillus polymyxa on field grown sorghum significantly increased grain and dry matter yields and N and P uptake as compared with single inoculation of individual microorganism (Alagawadi & Gaur, 1992). 3.11. Plant growth promotion and disease control studies (pot culture/farm level): The application of PGPR (plant growth promoting rhizobacteria) as crop inoculants for biofertilization, phytostimulation, and biocontrol would be an attractive alternative to reduce the use of chemical fertilizers which also effective to environmental pollution (Ali et al., 2010). The indirect growth promotion occurs via the removal of pathogens by the production of secondary metabolites such as siderophores and hydrogen cyanide (Idris et al., 2010). This is the first report of B. subtilis as a biocontrol agent against the banana leaf spots caused by various pathogenic fungi (Mycosphaerella) in the banana field. The possible mechanisms for strain of B. subtilis to suppress the banana leaf spot diseases could be considered as follows: (1) The production of the unidentified antibiotic substances by the antagonist led to control of the banana leaf spots and

36

(2) The systemic acquired resistance of the banana plants might be induced by the antagonist. It is an important requirement to obtain a biocontrol agent with a higher environmental stress tolerance and a wide antagonistic spectrum against multiple pathogens causing banana leaf spots for a successful field biocontrol of the these diseases. The stress-tolerant ability of B. subtilis was found to be stronger than other endophytic bacteria lacking spores in their life cycles (Gang et al., 2010). The banana, an important fruit crop, requires more amounts of chemical fertilizers for their commercial cultivation, which is very costly and can be harmful to the environment, when used extremely. The plant growth promoting rhizobacteria mostly used for plant growth promotion, nutrient uptake and the inoculation also fixed N2 in association with banana roots subsequently increased the yield, improved the physical attributes of fruit quality and initiated early flowering (Mia et al., 2010). The application of biocontrol agents those are safe for the environment as become an important strategy in integrated pest management for enhancing plant productivity and safety of agro-products. Several antagonists such as Trichoderma harzianum (Alvindia and Natsuaki, 2008), Burkholderia cepacia (De-Costa and Erabadupitiya, 2005), Bacillus amyloliquefaciens (Alvindia and Natsuaki, 2009), Pseudomonas syringae (Williamson et al., 2008) are reported. Khan and Doty, (2009) reported as: (a) Many endophytic microorganisms provide advantageous effects to their hosts such as to prevention of disease development by antifungal metabolites and synthesizing novel compounds. (b) Most of bacterial endophytes have been shown to support plant growth and increase nutrient uptake by providing phytohormones (IAA, Gibberellic acid), compounds with low molecular weight, enzymes, antimicrobial substances like siderophores and antibiotics. The strain of B. subtilis had a broad antagonistic spectrum against all the prevalent fungal pathogens which are mostly appeared on the banana leaves in Jinling Township, Nanning city where the farm level study were carried out (Fu et al., 2007). The inoculation process stimulate the reproductive growth as shown by early flowering (3 weeks) and improved bunch yield (51%).The earliness of flowering is attributed to early development of plants with efficient water uptake and nutritional value. The study reported an additional 3 weeks saving in the maturation period of bananas. This indicated that PGPR stimulated plants for early

37 reproductive development through improvement of nutrient uptake as reported by Mia, (2002). The growth of stomatal conductance and lowered the proline concentration in leaves of banana seedling grown under submerged condition PGPR (Plant growth promoting rhizobacter) inoculation performed most important role. It also alleviated plant stress due to submergence, while chlorophyll content, leaf growth and new root formation were lowered under submerged condition which reported by Shamsuddin et al., 1999. The plant growth promoting microorganisms are a group of organisms that have very closely related with plants and can help plants to establish in degraded ecosystems, to enhance growth of plant and protect plants from some diseases (Germida et al., 1998). The inoculation process could stimulate the development of roots and their growth (Mia et al., 1998), which occurred almost in all dimensions of the roots namely in the production of primary and secondary roots, longer roots and better mass and their volume. The micropropagated banana plantlets from the 'Grand Nain' cultivar were inoculated with mycorrhiza and rhizobacteria either alone or combined and the results showed that combined inoculated plants showed growth parameters i.e., whole fresh weight, aerial shoot length, dry weight and leaf area, significantly higher than non- treated control bananas. The mineral content i.e., N, P and K in the plant was also significantly increased following combined application of both microorganisms with there is no any adverse effect on mycorrhizal colonization due to Bacillus spp inoculation could be detected. The plant growth promoting effects of PGPR are mainly resulting from physiological and morphological changes in roots of inoculated plant (Okon et al., 1988; Sarig et al., 1988). Similar results have been also demonstrated by Tiwary et al. (1998), who found that inoculation of banana sucker with Azospirillum twice (sucker + soil inoculation) resulted in optimum plant height and leaf size of the plants receiving 50% of the recommended nitrogen dose to the plants. However, inoculation of Azospirillum had no significant response in reducing the time required for shooting from banana planting. The Azospirillum inoculated plants produced higher number of bunch with compensated 50% of the suggested dose of nitrogen and the number of hands/bunch obtained were at par with double booster. The inoculation of Azospirillum to the banana plant produced maximum yield of banana (69.15 t/ha). A quite high amount of total suspended solids (TSS) and reduced sugar content were recorded with

38 biofertilizer of Azotobacter inoculated to banana plants. But they did not find any reliable results on acidity of the banana fruit as well as total sugar content in the fruit. The PGPR improved root growth and function with a potential mechanism without any kind of affects on banana plant were proposed by Fallik et al., (1994).

39