In-Vitro Studies of Different Culture Media and Biocontrol Agents on Growth and Sporulation of Alternaria Alternata (Fr.) Keissler an Incitant of Broad bean (Vicia Faba L.) Leaf Blight Disease
Abstract
Studies on different culture media and biocontrol agents on growth and sporulation of Alternaria alternata (fr.) keissler causal organism of Broad bean (Vicia faba L.) leaf blight disease was conducted in vitro. Six culture media was tested for growth and sporulation of A. Alternata. It was found in that in liquid broth media, Potato dextrose broth (607 mg, dry weight of mycelium) and in solid media, maximum linear growth recorded in Potato dextrose agar (90 mm) with maximum number of spores 6.2 x 103 spores/ml. The antagonistic studies of 5 fungal biocontrol agents in dual culture technique found that all biocontrol agents statistically produced a significant antagonistic effect on linear growth and sporulation of A. Alternata. Maximum linear growth inhibition of Alternaria alternata was found in Trichoderma harzianum (17.5mm) with 89.6% inhibition and at par with Trichoderma viride (19.5mm) with 84.4% inhibition followed by T. hamatum (22.3 mm) with 74.1% inhibition and Gliocladium virens (21.0 mm) with 70.6% and minimum significant inhibition effect in T. koningii (22.8 mm) with percent inhibition of 67.2 over the check. Highest spore inhibition of was found in T. harzianum (89.6%) and T. viride (84.4%) followed by T. hamatum (74.1%) and G. virens (70.6%) while minimum inhibition was found in T. koningii (67.25). It was further observed that T. harzianum could overgrown the growth of pathogenic fungus within 2 days and for T. viride within 3 days whereas T. hamatum and G. virens took 5 days.
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Introduction
Broad bean (Vicia faba L.)is an important leguminous crop cultivated indifferent parts of mild sub-tropical and temperate regions of the world. In Manipur and northeastern state of India it is mostly grown as vegetable crop, where tender green pods were used as culinary purposes and mature seeds used as dals, snacks preparation and seed purposes. This important winter vegetable crop was often attacked by various diseases and out of eight major diseases recorded, blight disease caused by Alternaria alternata frkeissler is most serious (Gupta, 1985). The disease first appeared as small circular, brownish colour at the margin or tip of the leaf and progressed towards the midrib or the spots coalesce together to form into an elongated, irregular necrotic dark brown lesions. The affected young plants turn pale and leaf get drooping and wilted and die later. At present there is little information on physiology of the fungus associated with the blight disease and on management practices against this disease. Therefore the present investigation was taken up to study the effect of different types of culture media on the growth and sporuration of the pathogen and also to study the antagonistic effect of various bioagents against this pathogenic fungus.(Goswami and Mittal, 2002; Mittal et al., 2005 and Goswami and Mittal, 2004)
Conclusion
The data presented in the above Table 3, Fig. 4 & 5 is the antagonistic effect of biocontrol agents on the growth and sporulation of Alternaria alternata during dual culture test. It was found all biocontrol agents statistically produced a significant antagonistic effect on linear growth and sporulation of A. alternata. However, among the bioagents, maximum linear growth inhibition of the pathogenic fungi (A. alternata) was found in Trichoderma harzianum (17.5mm) with 89.6% inhibition over the check which was found at par with Trichoderma viride (19.5mm) with 84.4% inhibition followed by Trichoderma hamatum (22.3 mm) with 74.1% inhibition and Gliocladium virens (21.0 mm) with 70.6% and minimum significant inhibition effect was recorded in Trichoderma koningii (22.8 mm) with percent inhibition of 67.2 over the check. It was also observed that highest percent inhibition of sporulation of A. alternata was found in T. harzianum (89.6) and T. viride (84.4) followed by T. hamatum (74.1) and G. virens (70.6) while minimum percent inhibition was found in T. koningii (67.2). It was observed that T. harzianum could overgrown the pathogenic fungus within 2 days and T. viride within 3 days whereas T. hamatum and G. virens took 5 days. Our finding was in agreement with Basim and Katircioglu (1990) reported that in dual culture technique, bioagent Bacillus subtilis isolates could produce antagonistic activity against 7 (seven) fungal pathogens including Alternaria alternata. Similarly, Rajeshwari et al. (1998) reported that in dual culture test maximum inhibition of Macrophomina phaseolina was found in Trichoderma harzianum, Trichoderma viride and Gliocladium virens but least in Trichoderma koningii. Sudhakar et al. (1998) also reported that in dual culture technique Trichoderma viride was found superior in inhibiting the growth of Rhizoctonia solani, causal agent of rice sheath blight to Trichoderma harzianum. They also found lysis of the pathogen with the biocontrol agents.
