Studies on some aspects of maydis leaf blight of maize caused by Helminthosporium maydis Nisikado & Miyake
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Date
2008-06
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G.B. Pant University of Agriculture and Technology, Pantnagar - 263145 (Uttarakhand)
Abstract
Maize (Zea mays L.) is one of the important cereal crops in the world agricultural economy as food for man and feed for animal. Maize does possess tremendous potential in terms of food as bread, pops and gruel, feed for dairy, poultry and piggery agro-industries. Maize is vulnerable to numerous diseases at various growth stages in the field as well as during storage. Among them, maydis leaf blight of maize (MLB) caused by Helminthosporium maydis is an important disease particularly in warmer maize growing areas and causes significant yield losses. Some chemical control measures against the disease are there but a global voice of integrated management has created a strong need to work upon other avenues of disease management along with chemical management. The experiments were conducted on study of morphological characters of the pathogen, in vitro screening of antifungal activities of plant extracts and fungicides against H. maydis, evaluation of various fertilizers doses on the severity of the disease, testing the efficacy of fungicides for management of maydis leaf blight and screening of germplasm against maydis leaf blight of maize to find out the source of resistance against the disease. Microscopic study of the test pathogen (H. maydis) was done for the morphological characters of the pathogen. Hyphae were branched, septate and sub hyaline. Olive brown to
olivaceous conidiophores arose from these hyphae and emerged through the stomata singly or in groups of 2-3. The condiphores were simple, septate, erect and geniculate and measured 110-1796 μ in length and 6.2-10.8 μ in width. Conidia were light to olivaceous in colour and measured 30-112 x 10-16.5 μ. The dose of fertilizers i.e. NPK @ 100, 40, 40 kg/ha recorded minimum disease severity and maximum yield as compared to other combinations of NPK. Nine fungicides were tested for their fungicidal potential in vitro. Out of which propiconazole, chlorothalonil, triadimefon, mancozeb, saaf and thiram were found to be highly effective in reducing the radial growth of the pathogen.
Seed treatment @ 4 g/kg of seed and one foliar spray with propiconazole or chlorothalonil significantly reduced the disease severity and increased the yield. Two foliar sprays at 10 days interval with propiconazole @ 0.1% or chlorothalonil @ 0.2% also significantly reduced the disease severity and increased the yield. Plant extracts of garlic (Allium sativum), onion (Allium cepa) and datura (Datura alba) were found to be highly effective in reducing the colony diameter of H. maydis at the concentration of 20%. Out of 256 genotypes evaluated under artificial inoculation conditions, only one germplasm (POB.33 C3 142-1-6-1-1-4) showed highly resistant reaction and 54 entries/varieties indicated moderately resistant to resistant reactions against maydis leaf blight of maize.
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