Studies on karnal bunt of wheat with particular reference to its management by botanicals and bioagents
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Date
2006-06
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G.B. Pant University of Agriculture and Technology, Pantnagar - 263145 (Uttarakhand)
Abstract
Wheat (Trticum aestivum L.) is one of the primer food crop of the world. It is an important rabi cereal crop of family Poaceae. Wheat is vulnerable to numerous diseases at various growth stages in the field as well as during storage. Among them, the Karnal bunt caused by Neovossia indica (Mitra) Mundkur also referred as ‘New bunt’ or ‘Partial bunt’ was first reported from Karnal, India by Mitra in 1931. The disease affects both the quality and quantity of wheat grains. Wheat lots having 3.0 per cent infected grains are unacceptable for human consumption. The management of the disease is still a challenge to the scientists due to its complex disease-cycle and lack of information about the epidemiology of the disease. Thus, keeping this view and in order to understand the pathogen and disease better, the present investigations were undertaken to evaluate the cultural characters of N. indica insolate UP 262, effect of different pH on teliospore germination, radial growth and sporulation of N. indica, effect of plant extracts on teliospore germination of N. indica and antagonistic effects of soil mocro-organisms against N. indica.
A field experment was also conducted during rabi crop season , 2005-06 at Crop Research Centre, G.B. Pant University of Agriculture & Technology, Pantnagar to study the effect of fungicides, botanicals, bioagents and their integration against Karnal bunt of wheat for its management and their effect on yield components by using susceptible wheat cultivar UP 262.
The results revealed that out of three media tested, potato dextrose agar medium was found best for growth and sporulation of N. indica isolate. In broth media, glucose yeast extract agar medium supported fairly good growth but least sporulation, whereas potato dextrose broth supported higher sporulation of the isolate.
pH 5.5 was found optimum for teliospore germination. No teliospore germination was found below pH 4 or above pH 12. Optimum pH for growth and sporulation was found to be pH 6.0. pH 5.0 gave minimum radial growth and pH 4.0 gave minimum sporulation of N. indica isolate.
Botanicals (Neem, Ginger) completely inhibited the teliospore germination of N. indica isolate in standard extract (SE) and 1:10 dilution of SE.
Bioagents (T. harzianum, Aspergillus spp, Bacillus spp) inhibited the growth of the test fungus. T. harzianum did not allow N. indica to produce secondary sporida. Hyphac of N. indica interacting with .T. harzianum and Aspergillus spp. showed high vacuolation. Bacillus spp. inhibited the growth of N. indica when it came in contact with it and an inhibition zone was formed between the two. Hyphae of the test fungus showed abnormality as they got shriveled and curved.
Seed treatment with Tilt 25 EC @ 1 ml/ kg seed and Castor @ 5 mll/ kg seed produced 938.00 and 935.33 gm plot yield which exhibited 16.52 and 16.08 per cent yield increase over check respectively.
Castor @ 5 ml/ kg seed produced maximum no. of grains and weight of grains per ear. T. harzianum @ 4 g/ kg seed + Tilt 25 EC @ 1 ml/ kg seed produced higher length of ear heads followed by Eucalyptus globulus @ 5 ml/ kg seed.
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