Bull. Inst. Trop. Agr., Kyushu Univ. 39: 43-51, 2016 43 Biological control of leaf blight of wheat caused by Bipolaris sorokinian M.M. Hossain1)*, I. Hossain2) and K. M. Khalequzzaman3) Abstract Five different plant extracts including neem (Azadirachta indica), mehedi (Lawsonia alba), garlic clove (Allium sativum), rhizome of ginger (Zingiber officinales), seeds of black cumin (Nigella sativa), and BAU-Biofungicide (a Trichoderma based preparation) were used to evaluate the performance or effectiveness of those biological control agent on Bipolaris leaf blight of wheat and related pathogen (Bipolaris sorokiniana). Pathogenic reaction was observed in Bipolaris sorokiniana against different treatments by detached leaf method where leaf spot size was minimum (4.5mm) with BAU-Biofungicide and maximum leaf spot size (32.5mm) with control. Effect of seed treat- ment on wheat plant was evaluated by rolled paper towel method and BAU-Biofungicide, extracts of garlic clove and neem leaf at the value of 13%, 12% and 10%, respectively higher normal seedlings and BAU-Biofungicide also resulted 26.6% higher vigour index over control. Multiplication effect (seed treatment plus foliar spray of same treat- ment) of different treatments was examined to determine the efficacy for disease control. In pot and field experi- ments, though Bavistin and Tilt were most effective however, BAU-Biofungicide and extract of garlic clove were superior compared with the treatments used for controlling leaf blight of wheat. Multiplication effect of seed treat- ment plus foliar spray showed superior effect by BAU-Biofungicide including higher 1000-grain weight (43.92g) and grain yield (2.75 t/ha). Seed treatment with Bavistin and foliar spray with Tilt showed 1000-grain weight and grain yield by 47.12g and 3.0 t/ha, respectively. Our data also revealed that BAU-Biofungicide increased grain yield (29.87%) over control. Keywords: Detached leaf, BAU-Biofungicide, AUDPC and extract Introduction Wheat (Triticum aestivum L.) is considered as one of the most important cereal crops in the world and it became to the second most important in Bangladesh. The average yield of this crop is only 2.60 ton/ha in Bangladesh (BBS, 2012) and damage caused by disease become to the main constraints of high yield. Leaf blight caused by Bipolaris sorokiniana of wheat is the most common and severe dis- ease and the severity of the disease has been increased in an alarming proportion (Bazlur Rashid et al., 1987; Hossain and Azad, 1994; Alam et al., 1995). It causes foliar blight, seedling blight, head blight and common root rot of wheat (Hossain, 1991; Hossain and Khan, 1993; Hossain and Azad, 1994; 1) Senior Scientific Officer, Regional Agricultural Research Station, BARI, Jamalpur, Bangladesh 2) Professor, Department of Plant Pathology, BAU, Mymensingh, Bangladesh 3) Senior Scientific Officer, Spices Research Centre, BARI, Shibganj, Bogra, Bangladesh *Corresponding author: [email protected] 44 M.M. Hossain et al. Shahzad et al., 2009). This disease is major constraint of wheat cultivation causing severe reduction of yield up to 40% and 88% over control, under natural field condition and artificial inoculation, respec- tively (Hossain et al., 1998). The high morphological, physiological and genetic variability makes the control of this fungus due to a difficult task (Poloni et al., 2009) and the yield loss of this disease ranged from 10-21% (Hossain and Azad, 1992; Malaker et al., 2004). The use of chemicals, has been found very effective in controlling fungal diseases of plant, but some major problems threaten to limit the continuous use of fungicides. Many research workers have tried to find out safe and economical control of plant diseases by using extracts of different plant parts (Akhter et al., 2006; Bdliya and Alkali, 2008). Plant extracts and biofungicide are also available to treat seed (Koike et al., 2011) In several studies’ it has been found that plant extract increased seed germination and vigour index in different crops after application of plant extracts (Hasan et al., 2004; Chowdhury et al., 2005a). The application of Trichoderma harzianum has been identified as potential biocontrol agents for the man- agement of various crop diseases (Venn, 2011). This biocontrol agent has the potential to protect seed- lings against several plant pathogenic fungi (Kucuk et al., 2007; Hasan and Alam, 2007). Trichoderma spp. is effective to reduce the foliar disease severity on wheat plants compared with untreated plants (Muthomi et al., 2007; Hasan and Alam, 2007; Sing et al., 2008). Hossain and Sultana (2011) stated that the BAU-Biofungicide effectively manage the seed and seedling diseases of maize. Biological control represents a natural and ecological approach for controlling diseases the reduce the usage of chemical inputs and their effects on environment. It is more stable and longer lasting than the controls and is comparative with the concepts and goals of integrated pest management and sustain- able agriculture. Concerning to the health, safety and environmental effects of agricultural chemicals in our water, soil and food, the use of biological control need to be emphasized strongly. Biological control has now become one of the most exciting and rapidly developing areas in plant pathology, because it has great potential to solve many agricultural and environmental problems. Biological con- trol has been proposed as a replacement for chemical control of plant diseases. However, the present study was under taken to develop a suitable biological control approach for the management of leaf blight of wheat with out use any chemicals. Materials and Methods Collection of seeds, plant materials and BAU-Biofungicide The seeds of wheat variety Kanchan (highly susceptible to leaf blight) were collected from Regional Agricultural Research Station (RARS), Jessore. Five plant materials including leaves of neem (Azadirachta indica), mehedi (Lawsonia alba), garlic clove (Allium sativum), rhizome of ginger (Zingiber officinales) and seeds of black cumin (Nigella sativa) were collected from Botanical garden of Bangladesh Agricultural University (BAU) and local market of Mymensingh. BAU-Biofungicide (a Trichoderma based preparation) was obtained from the Disease Resistance Laboratory of the Depart- ment of Plant Pathology, BAU, Mymensingh. Biological control of Bipolaris sorokiniana 45 Seed treatment Required amount of seeds presented each treatment with plant extracts (at 1% suspension), BAU- Biofungicide (at 2.5% seed weight) and Bavistin (at 0.1%) separately over night by dipping method and then separate the seeds by air dried. 1% suspension of plant extracts. Plant extracts and BAU-Biofungi- cide were prepared according to the method of Hossain and Azad (1994) and Hossain (2011). Excised leaf method and rolled paper towel method were performed the according to the method of Hossain and Schlosser (1993) and Singh and Rao (1997). The preparation of B. sorokiniana inoculum followed CIMMYT method (Gilchrist, 1985). Sowing of seeds in pot Treated seeds were sown in pots (10 seeds /pot) at 2 cm depth in the soil with four replications. Irrigation and weeding were carried out and thinned to five seedlings. Preparation of pot soil was done following the method of Dasgupta, (1988). Experiments were conducted in the laboratory and experimental field of the Department of Plant Pathology, BAU, Mymensingh, Bangladesh. Completely randomized design with 4 replications in pot and randomized block design with three replications in field experiments were maintained. The plot size was 10 m2 and date of sowing was 6th December, 2011. Application of spray materials Plant extracts (1%), BAU-Biofungicide (2%) and Tilt 250 EC (0.05%) were sprayed at 12 days inter- val commencing just after appearance of disease symptom. Data collection and analysis Data on percent germination, percent abnormal seedlings, shoot and root length, yield and yield contributing characters were collected and analyzed. Vigour index (VI) was computed using the for- mula of Baki and Anderson (1973) as shown below: Vigor index= (Mean shoot length + Mean root length) x percent Germination Leaf blight severity was scored three times on double digit scale (00-99) reported by Saari and Prescott (1975) commencing from the water ripe to early dough stage (Zadoks et al. 1974). Disease data were converted to percent diseased leaf area (percent DLA) and then area under disease progress curve (AUDPC) was calculated according to the method of Sharma and Duveiller (2003). % DLA = D1/9 X D2/9 X 100 where, D1 = First digit, representing relative disease height D2 = Second digit, indicating disease severity on the foliage n AUDPCAUDPC == [(Y[(Yi+1i+ 1+ + Y Yi)i) xx 0.5]0.5] [[TTii+1+1 - Tii]] i=1 where, Yi = Disease severity at the ith observation, Ti = Time (days) of the ith observation and n = Total number of observations (at least 3 observations). 46 M.M. Hossain et al. Results and Discussion Pot and field experiments were conducted to determine the combined effect of seed treatment plus flower spray with 5 plant extracts and BAU-Biofungicide in controlling leaf blight of wheat in vitro. Inhibition of pathogenic reaction caused by B. sorokiniana by using five plant extracts and BAU- Biofungicide were investigated following detached leaf method by artificial inoculation of wheat vari- ety Kanchan with 6x104 conidia/ml in-vitro. No lesion was produced by the pathogen (B. sorokiniana) when Bavistin (0.1%) used on one and two month old seedlings. Only 4.5 mm lesion was produced in case of BAU-Biofungicide and 32.5mm in control (Table 1). The result of the experiment is in agree- ment with the findings of Galletti et al., (2008). Hossain and Ashrafuzzaman (1994) and Hossain et al (1997) reported that garlic clove and mehedi leaf completely inhibited the pathogenecity of B. sorokini- ana on the excised wheat leaf. Effect of seed treatment with different plant extracts and BAU-Biofungi- cide on percent germination, percent normal seedlings and vigour index of wheat seeds were investi- gate. All treatments showed increased germination significantly over untreated control in pot and in- vitro conditions.