Yogesh KumarRoomi Devi2022-07-182022-07-182019-06https://krishikosh.egranth.ac.in/handle/1/5810185513The present investigation was carried out at CCS Haryana Agricultural University, Hisar during Kharif seasons of 2017 and 2018. A survey of cotton growing areas was done in north region of India viz. Haryana, Punjab and Rajasthan and whitefly samples were collected to find out the molecular variation among whitefly. MtCOI gene specific primers were used to amplify the mtCOI gene segment of extracted DNA of whitefly. Screening of forty cotton genotypes were done against whitefly and level of resistance was further correlated with different biochemical and morphological traits. Different crops like sorghum, bajra, pigeon pea, cowpea and sesame were grown as intercrops with cotton to know their effects on whitefly population. Efficacy of different pesticides were tested against whitefly. For this two spray were done at ETL and data was recorded before spray and 1st, 3rd, 7th and 10th DAS. Results revealed that in all the samples mtCOI gene segment were amplified at 1000bp band. Sequences were generated from these samples and aligned along with reference sequences all over the world representing seven different clades of B.tabaci to analyse phylogenetic relationship. It was found that our sequences belong to Asia II-1 and clustered in clade of representing Asia II-1 biotype from Northern region of India. During both the years population of whitefly commenced in month of June (24th SMW) and continued till harvest of crop (41st SMW) with two peaks. Observations during Kharif 2017, 2018 and pooled analysis of both the years showed that maximum population was recorded in ARBH 1601 (15.81, 9.76, 12.79 adults/leaf) and minimum in HS 286 (10.03, 5.21, 7.62 adults/leaf), respectively. Whitefly population showed significant negative correlation with maximum temperature and significant positive with morning relative humidity. Population of whitefly showed significant and positive correlation with total sugar content, trichomes density while non significant and positive with protein and chlorophyll content. Significant and negative correlation with phenol, tannin and leaf thickness. Intercropping system revealed significant suppression in all the intercropped treatments over the sole cotton crop. Pooled mean of both the years revealed that minimum population was recorded in cotton intercropped sorghum (3.69 adults/leaf) and maximum in sole cotton (10.82 adults/leaf). Pooled mean of both the years 2017 and 2018 showed that the flonicamid 50% WG @ 150 g/ha (68.65%) was the most effective insecticide while Verticilium lecanii 1.15WP @ 2.5kg/ha (41.11%) was least effective.EnglishThesis