Studies on Variability and Management of Spot Blotch of Wheat

Abstract

Wheat is a staple food for nearly 38 percent of world's population. Production of ~heat needs to be in~reased to fulfill the increasing demands in coming decades. To 1~crease the production, management of disease is a prime concern. Among the diseases, spot blotch of wheat caused by Bipolaris sorokiniana has become a major cause of concern for farmers and researchers as well in the post green revolution scenario. Applications of balanced dose of fertilizers and micronutrients have resulted in reduction of disease severity. At the same time knowledge about the variability of pathogens is another important point in the management of disease. In the present investigation molecular virulence diversity of 12 isolates of B. sorokiniana was carried out and also the effect of different micronutrients, fungicides, bio-agents and botanicals on spot blotch were studied under field conditions. Among 20 RAPD primers tested, 11 RAPD primers showed 1 00°/o polymorphism with an average of 20.25 bands per primer while 9 RAPD primers gave monomorphic bands. A total of 57 alleles were detected from 12 isolates of B. sorokiniana. The highest number of alleles were observed due to primer OPP-04 (seven alleles), followed by OEP-14 (six alleles) and OPW-05 (five alleles). According to dendogram B. sorokiniana isolates were grouped into two major distinct clusters i.e. cluster IIA and liB, cluster IIA consists of two isolates i.e. MeerutHallana and Hisar WH-542 with a similarity coefficient of 0.632 while cluster liB consists of remaining 10 isolates with a similarity coefficient of 0.84. Application of manganese followed by zinc, Boron, Molybdenum, Iron & Sulphur resulted in minimum disease incidence, severity and increasing yield. In case of fungicides, Carbendazim resulted in maximum reduction of spot blotch incidence and severity and gave highest yield followed by Mancozeb & Propiconazole. In case of b~o-agents . Pseudomon~s fluorescence found to be superior than Trichoderma harz1anum wh1ch resulted 1n highest reduction in incidence. It was almost equally e_ffe.cti~e in reducing ~pot blotch severity also. In case of botanicals maximum reduction 1n 1nc1dence was not1ced due to application of Eucalyptus leaf extract followed by neem leaf extract, where a~ neem cake was found to be effective for highest reduction of spot blotch seventy and Eucalyptus leaf gave the highest yield as compared to other botanicals.