Banyal, D.K.Kaur, Gurpreet2018-09-122018-09-122018-07http://krishikosh.egranth.ac.in/handle/1/5810072831The investigation entitled “Variability in Phytophthora nicotianae var. parasitica causing buckeye rot of tomato and its sensitivity to fungicides” was conducted at Department of Plant Pathology, CSKHPKV Palampur during 2016-2018. More than 25 samples of buckeye rot were collected from six districts of Himachal Pradesh and the pathogen was isolated and purified from 17 samples. The identity of the pathogen was confirmed on the basis of symptoms, morphological and cultural characteristics. The cultural and morphological variability divided the 17 isolates into 4 and 3 groups, respectively. Molecular data generated by ISSR markers exhibited genetic diversity in Phytophthora nicotianae var. parasitica isolates placing 17 isolates into 5 variant groups at 64 per cent similarity. All the isolates were sensitive to mancozeb 75WP (Indofil M-45), copper-oxychloride 50WP (Blitox-50) and metalaxyl-M 4%+ mancozeb 64%WP (Ridomil Gold) under in vitro. However, level of sensitivity of isolates varied within the same fungicide as well as between different fungicides as high, moderate and less sensitive. Evaluation of aqueous extract of botanicals namely Ocimum sanctum, Melia azedarach, Lantana camara, Eucalyptus sp. and Eupatorium adenophorum revealed that Melia azedarach inhibited maximum growth (70.00%) of Phytophthora nicotianae var. parasitica under in vitro. In vitro evaluation of bioagents viz., Trichoderma koningii (DMA-8), Trichoderma koningii (JMA-11), Trichoderma harzianum (SMA-5) and Trichoderma viride showed that Trichoderma koningii (DMA-8) gave maximum (53.42%) mycelial inhibition of P. nicotianae var. parasitica. Among 8 fungicides tested in vitro against P. nicotianae var. parasitica, iprovalicarb 5.5%+ propineb 61.25% WP (Melody Duo 66.75 WP) at 100 μg/ml, metalaxyl-M 4%+ mancozeb 64%WP (Ridomil Gold) at 250 μg/ml, propineb 72WP (Antracol) and cymoxanil 8%+ mancozeb 64% WP (Curzate 72 WP) at 500 μg/ml, mancozeb 75WP (Indofil M-45) and copper-oxychloride 50WP (Blitox-50) at 750 μg/ml and azoxystrobin 23% SC (Mirador) at 2000 μg/ml inhibited 100 per cent mycelial growth. In a field trial conducted during 2017 & 2018, it was observed that foliar application of iprovalicarb 5.5%+ propineb 61.25% WP (@0.25%) resulted in maximum (54.72%) disease control with 81.51 per cent increase in yield over check followed by metalaxyl-M 4%+ mancozeb 64% WP (@0.25%) which gave 50.63 per cent disease control with 78.34 per cent increase in yield. Copper-oxychloride 50WP (@0.30%), mancozeb 75WP (@0.30%) and propineb 72WP (@0.25%) were also found effective and gave 49.32, 43.61 & 43.07 per cent disease control with 76.84, 64.62 & 62.37 per cent increase in yield over check, respectively.ennullThesis