Fungi Associated with Storage Rots of Colocasia Esculenta L. Tubers in Bhubaneswar City, Odisha

Home , Geotrichum candidum, Rhizopus oryzae

British Microbiology Research Journal 12(3): 1-5, 2016, Article no.BMRJ.23137 ISSN: 2231-0886, NLM ID: 101608140

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Fungi Associated with Storage Rots of Colocasia esculenta L. Tubers in Bhubaneswar City, Odisha

Akhtari Khatoon1, Ashirbad Mohapatra2 and Kunja Bihari Satapathy1*

1Department of Botany, Utkal University, Vani Vihar, Bhubaneswar-751004, Odisha, India. 2Sri Jayadev College of Education and Technology, Naharkanta, Bhubaneswar-752101, Odisha, India.

Authors’ contributions

Authors KBS and AM supervisors of this project and author AK student carried out project as component of requirements for Ph.D. of Utkal University. All authors read and approve the final manuscript.

Article Information

DOI: 10.9734/BMRJ/2016/23137 Editor(s): (1) Laleh Naraghi, Plant Disease Research Department, Iranian Research Institute of Plant Protection, Tehran, Iran. Reviewers: (1) M. Angels Calvo Torras, Autonomous University of Barcelona, Spain. (2) Anonymous, Kansas State University, Manhattan, USA. Complete Peer review History: http://sciencedomain.org/review-history/12810

Received 16th November 2015 Accepted 7th December 2015 Original Research Article Published 28th December 2015

ABSTRACT

A survey of fungi associated with post-harvest deterioration of Colocasia esculenta L. tubers was conducted in Bhubaneswar city, Odisha, India, in 2014-15. Rotten Colocasia esculenta L. tubers collected from five different markets: Unit-I market, Sahid Nagar, V.S.S. Nagar, Palasuni and Rasulgarh market located in Bhubaneswar city. The following fungi; Aspergillus niger, Aspergillus flavus, Geotrichum candidum, Rhizopus oryzae were isolated from rotten tubers. Of these, Rhizopus oryzae and Geotrichum candidum has highest percentage frequency of occurrence followed by Aspergillus niger while Aspergillus flavus has the least percentage frequency. Pathogenicity tests revealed that all the isolated fungi were pathogenic on Colocasia esculenta L. tubers; however Rhizopus oryzae and Aspergillus flavus were most pathogenic leading to rapid disintegration of the infected tubers within 20 days of inoculation. While Aspegillus niger was the least pathogenic. The use of improved Colocasia esculenta L. varieties, good storage facilities and adequate control measures need to be encouraged in order to reduce storage rot of Colocasia esculenta L. tubers.

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*Corresponding author: E-mail: [email protected];

Khatoon et al.; BMRJ, 12(3): 1-5, 2016; Article no.BMRJ.23137

Keywords: Taro tubers; fungi; storage rots; post-harvest losses; markets.

1. INTRODUCTION significance of the present work lies with the rapid incidence of postharvest decay of the Colocasia esculenta L. is used as a staple food vegetable and its management with special or subsistence food by millions of people in the reference to Odisha. developing countries in Asia, Africa and Central America [1]. It has much importance in ensuring 2. MATERIALS AND METHODS food security. Nutritionally, C. esculenta contains more than twice the carbohydrate content of 2.1 The Study Area potatoes and yield 135 k cals per 100 g [1]. It contains about 11% protein on a dry weight The study was conducted in the P.G. Department basis. This value is more than cassava, yam or of Botany, Utkal University, Bhubaneswar, sweet potato. C. esculenta contains 85-87% Odisha, India. Bhubaneswar city is located in the starch on dry matter basis with small granules 20.27° N and 85.84° E. It is in the eastern size of 3-18 μm and other nutrients such coastal plains, along the axis of the Eastern as minerals, Vitamin C, thiamin, riboflavin and Ghats Mountain. The city has an average altitude niacin better than other cereals [1]. Nowadays, of 45 m (148 ft) above sea level [12]. C. esculenta is considered as the fifth most Bhubaneswar has a tropical savannah climate. consumed root vegetable worldwide [2]. The annual mean temperature is 27.4°C (81.3°F); monthly mean temperatures are 22- Colocasia esculenta L. is an emergent, 32°C (72-90°F). The area has an average annual perennial, aquatic and semi-aquatic herbaceous rainfall of 1,542 mm. The highest monthly rainfall species belonging to the family Araceae, native was 330 mm (13 in), occurs in August [13]. to Asia. As a root vegetable, this plant is grown primarily for its edible corms [2]. Post-harvest 2.2 Collection of Samples loss of root and tubers has been of serious problem to farmers and warring against food security [3]. Colonization of the tubers by fungi Colocasia esculenta L. tubers showing will lead to reduction in consumption materials, symptoms of rotting were randomly selected from market value and production of mycotoxins [4]. five different markets: Unit-I, Sahid Nagar, V.S.S. Various fungus especially oomyceteous plant Nagar, Palasuni and Rasulgarh located in pathogens of C. esculenta have been reported to Bhubaneswar city. The tubers were collected and cause losses in its fields [5]. A major limiting kept separately in sterile polythene bags and factor in worldwide C. esculenta production is brought to the Microbiology laboratory of Utkal leaf blight disease caused by Phytophthora University, Bhubaneswar for phytopathological colocasiae [5]. Ceratocystis fimbriata is one of analysis. the major fungi that can be associated with its root rots causing rot of storage corms of 2.3 Isolation and Identification of C. esculenta worldwide [6]. Several common soil Associated Fungi borne microorganisms such as Phytophthora citricola, Phytophthora nicotianae, Pythium spp., The diseased tubers of Colocasia esculenta L. Fusarium oxysporum, Fusarium solani, were washed with tap water and surface Sclerotium rolfsii and Rhizoctonia sp. may also sterilized with 0.1% mercuric chloride solution for be responsible for the root rot of C. esculenta 2-3 minutes. The tubers were cut through by [7,8]. Pythium carolinianum is mostly associated means of sterile knife. Slicing was done starting with the rotting of wetland tubers rather than dry from the healthy portions. Pieces of 5 × 5 mm land tubers [9]. Phytophthora blight caused by were cut and placed on potato dextrose agar Phytophthora colocasiae and Pythium root and (PDA) medium and incubated at room corm rot caused by Pythium spp. are the most temperature for 24 to 35 hours. serious fungal diseases of C. esculenta [10]. Ceratocystis fimbriata was found to sporulate on Representative colony types were purified by edible corms of C. esculenta [11]. sub-culturing on fresh PDA plates. Pure cultures were transferred to slants of PDA. Pure cultures The present study was carried out to isolate and of the isolates were grown singly on PDA for identify fungi associated with storage rot of identification. The isolated fungi were identified C. esculenta tubers in Bhubaneswar city. The based on the isolates colonial characteristics on

Khatoon et al.; BMRJ, 12(3): 1-5, 2016; Article no.BMRJ.23137

culture plates and microscopic features in slide 3. RESULTS cultures. Using a sterile inoculating needle portion of each mycelial colony was aseptically 3.1 Isolation of Fungi from Rotten taken and placed on a clean microscopic slide Colocasia esculenta L. Tubers and teased in a drop of lacto-phenol cotton blue. The isolates were identified by the help of the A total of fungal pathogens isolated 4 available literature and further authentication was fungal pathogens were isolated from rotten made in the Department of Microbiology, Odisha C. esculenta tubers. The results indicated University of Agriculture and Technology, that Aspergillus niger, Aspergillus flavus, Bhubaneswar. Geotrichum candidum and Rhizopus oryzae

were responsible for rot of storage tubers in 2.4 Pathogenicity Test Bhubaneswar city. Rhizopus oryzae and Geotrichum candidum had highest percentage of Fresh and healthy tubers of C. esculenta were frequency of occurrence followed by Aspergillus washed with tap water and surface sterilized with niger, while Aspergillus flavus has the least 0.1% mercuric chloride solution for 2-3 minutes. percentage of frequency. The results are Cylindrical cores were removed from the tubers presented in Table 1 and Fig. 1. with the help of 5 mm cork borer. Four millimetre (4 mm) agar discs containing 7 days old cultures of the isolates were introduced into the holes and Table 1. Fungi isolated from rotten Colocasia sealed with the sterile Vaseline. Controls were esculenta L. tubers set up as described except that the inocula consist of uninoculated potato dextrose agar Sl. Fungi Frequency of blocks. All the treated tubers were put singly into no. occurrence (%) sterile polythene bags and inoculated at 28±2°C 1 Rhizopus oryzae 30.2 for 10 days. The tubers were cut through and 2 Geotrichum candidum 21.3 examined for the extent of rotting at the end of 3 Aspergillus niger 10.5 the incubation period. 4 Aspergillus flavus 4.6

Fig. 1. Fungi isolated from rotten Colocasia esculenta L. tubers

Khatoon et al.; BMRJ, 12(3): 1-5, 2016; Article no.BMRJ.23137

Fig. 2. Pathogenicity of the isolates on Colocasia esculenta L. tubers

3.2 Pathogenisity Test oryzae. Rhizopus oryzae resulted in highest frequency of occurrence i.e. 32.2% followed by The pathogenicity test revealed that all the fungal Geotrichum candidum (21.3%), Aspergillus niger isolates were pathogenic on colocasia tubers. (10.5%) while the least frequency was shown by R. oryzae was the most virulent fungus followed Apergillus flavus i.e. 4.6%. by Geotrichum candidum and Aspergillus niger was the least virulent fungus. The results The results of the pathogenicity test revealed that of pathogenicity test are shown in Table 2 and among the fungi that were isolated R. oryzae Fig. 2. was the most virulent one causing the diameter of rotting around 44 mm followed by rest fungi Table 2. Pathogenicity of the isolates on i.e. Aspergillus flavus (33 mm), Geotrichum Colocasia esculenta L. tubers candidum (24 mm) while Aspergillus niger was observed to be a least virulent one (14 mm).

Sl. no. Fungi Diameter of 5. CONCLUSION rot in mm 1 Rhizopus oryzae 44 The present study revealed that many fungi have 2 Aspergillus flavus 33 been found to cause storage rot of Colocasia 3 Geotrichum candidum 24 esculenta tubers during storage condition in 4 Aspergillus niger 14 Bhubaneswar city. These pathogens lead to enormous loss of these tubers not only in terms 4. DISCUSSION of quantity but also reduce its economic and nutritive value. Some of these fungi are capable Studies on the fungi associated with storage of producing mycotoxins which are hazardous to decay of Colocasia esculenta tubers in the health of consumers. As such urgent Bhubaneswar city revealed that four species of attention is required for the disease, thereby fungi were responsible for the post-harvest loss increasing the economic yield of the produce. of the crop such as Aspergillus niger, Aspergillus This will ensure substantial contribution of the flavus, Geotrichum candidum and Rhizopus crop to food supply and national economy.

Khatoon et al.; BMRJ, 12(3): 1-5, 2016; Article no.BMRJ.23137

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