STUDIES ON SPOT BLOTCH [BIPOLARIS SOROKINIANA (SACC.) SHOEM.] OF WHEAT AND ITS MANAGEMENT
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Date
2016
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Division of Plant Pathology, Sher-e-Kashmir University of Agricultural Sciences & Technology of Jammu, Main Campus, Chatha, Jammu-180009
Abstract
The investigation regarding variability and management of Bipolaris sorokiniana, the causal organism of spot blotch of wheat and the yield loss caused by it was carried out during the year 2014-15. The disease was reported in all the wheat growing areas of Jammu subtropics with the maximum AIDX observed in Kathua district with the range of 29.55-48.15 per cent, followed by Samba ranging from 29.28-45.82 per cent. However, minimum disease was observed in Jammu district (30.06-40.61%).
The pathogenicity of B. sorokiniana isolates (BS1 to BS10) on cv. Sonalika revealed maximum AIDX (49.10%)) in isolate BS9 and least in BS10 (25.42%). Cultural and morphological variability of B. sorokiniana isolates exhibited that the colonies were effuse grey-white to effuse black and velvety-white mycelial growth with regular to irregular margins. The colour of colonies varied from grey to dark brown and white to light grey. The number of septation in isolates ranged from 3.9 to 6.3 and spore size ranged from 35.07 to 60.53μm in length and 13.20 to 17.60μm in breadth. The shape of the spore was elliptical, slight curved and straight with tapered end. All the isolates (BS1 to BS10) showed excellent growth on PDA while on CDA and PCA medium they showed fair growth. On the basis of pathogenic response of B. sorokiniana isolates on different wheat genotypes, isolates BS2 and BS9 were categorised as highly virulent, whereas isolates BS7 and BS10 as least virulent. Isolates BS2, BS3, BS4, BS5, BS6 and BS8 were moderately virulent. The loss in grain yield varied from 9.43 to 27.88 per cent depending upon the disease severity in different genotypes, while in genotype Sonalika highest loss in 1000 grain weight (15.43%) was noticed followed by PBW-550 (13.14%) and least in HD-2967 (3.48%) was observed.
Sixty two wheat genotypes were screened against spot blotch disease under artificially inoculated field conditions. Wheat genotypes viz. HD-2967, HD-3043, HP-1102, HS-277, JAUW-598, PBW-660, PBW-692 and VL-907 were reported as resistant, while as, DBW-88, DL-784-3, DPW-621-50, HD-2733, HD-3059, HD-3086, HI-1563, HS-1138, HS-207, HS-375, HS-490, HS-507, HS-542, JAUW-584, JAUW-595, Narmada-112, RSP-561, VL-892, WH-1021, WH-1080, WH-1105, WH-1124, HS-507, RAJ-4037, HS-542, PDW-291 and PDW-314 were ranked as moderately resistant against B. sorokiniana.
Propiconazole and tebuconazole both at 0.01 per cent were most effective, completely inhibiting the mycelial growth of pathogen (BS9) followed by difenconazole (96.27%) at same dose, whereas, Trichoderma harzianum-1 proved best among the bioagents tested, inhibiting 77.90 per cent of mycelial growth of the pathogen under dual culture method. In field studies, propiconazole @ 0.1% significantly reduced the spot blotch disease (75.50%) and increased grain yield by 27.20 per cent of wheat followed by azoxystrobin, which also reduced disease severity (74.09%) and increased grain yield by 24.83 per cent of wheat.