STUDIES ON TOXIN PRODUCTION, VARIABILITY AND MANAGEMENT OF TURCICUM LEAF BLIGHT OF MAIZE CAUSED BY Exserohilum turcicum (PASS.) LEONARD AND SUGGS. NATARAJ, K. DEPARTMENT OF PLANT PATHOLOGY COLLEGE OF AGRICULTURE, RAICHUR UNIVERSITY OF AGRICULTURAL SCIENCES, RAICHUR–584 104 JULY,
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Date
2014-07-30
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UNIVERSITY OF AGRICULTURAL SCIENCES, RAICHUR
Abstract
Turcicum Leaf Blight (TLB) caused by Exserohilum turcicum (Pass.) Leonard and Suggs is one of the important diseases affecting foliage with severe reduction in grain yield to an extent of 28 to 91 per cent. The maximum PDI of 51.39 was noticed in Davanagere and least was in Raichur (46.70 %) during Kharif 2013. Potato dextrose agar supported an excellent nutrient to all isolates for growth and development and least was in Richard’s agar. The potato dextrose broth supported an excellent dry mycelial weight to all isolates and least was in maize meal broth. Twenty five isolates were categorized into seven groups, based on cultural and morphological characters. Twenty five isolates were amplified with range of 500 to 520 bp length. Sixteen isolates were sequenced and deposited in the GenBank Maryland, USA database under the accession number KJ956045-KJ956060. The toxin was extracted and subjected to the analysis of UV, IR, HNMR and Mass spectroscopy which revealed the structural formula of the pathotoxin. In the bioassay of toxin, the maize hybrid HTMH-5106 gave resistant reaction, whereas the increased concentration enhanced the inhibition of seed germination and decreases in shoot and root length. In screening, four hybrids were moderately resistant. Remaining 19 were susceptible reaction. The contact fungicides, copper oxy chloride and propineb recorded maximum inhibition of mycelial growth. Among systemic fungicides, propiconazole, hexaconazole, difenoconazole, tebuconazole, triadimefon and hexaconazole 4 % + zineb 68 % showed 100 per cent inhibition at all concentrations. Among bio agents, Trichoderma viride (Tv-1) and (Tv-2) were found more effective. The seed treatment with captan @ 2 g/kg, first spray of hexaconazole 4 %+ zineb 68 % @ 0.15 per cent and second spray of P. fluorescens-RP-46 @ 0.5 per cent at 50 and 60 DAS was found more effective for controlling disease and subsequently gave higher yield.
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