JAGADISH, K. S.SHADHANAIKURAL, A.2017-03-062017-03-062009-09-12Th-9448http://krishikosh.egranth.ac.in/handle/1/5810003899Field screening of 106 sunflower genotypes revealed that the incidence of Thrips palmi ranged from 0.00 to 2.25/ plant and that of sunflower necrosis disease (SND) ranged between 0.00 to 100.00 per cent. Based on SND incidence,10 genotypes(GMU 685, 650, 664,662, 661,613, 676, KBSH53, KBSH 53 A & RHA 95-C-l) were shortlisted as highly resistant ,while another 10 genotypes viz., GMU-700, 637, 669, 632, 696, 682, 698, KBSH-44, Morden & CMS-17A were shortlisted as highly susceptible to SND. The 10 resistant entries recorded greater trichome density and length as compared to the 10 susceptible entries. Trichome density was significantly, negatively correlated with thrips population and SND. Similarly, trichome length was negatively correlated with the incidence of both thrips and SND, however, this correlation was non-significant. Majority of SND resistant entries possessed coarse lamina, while most of the susceptible entries exhibited smooth lamina. The total soluble sugar (TSS) content was lower in the 10 resistant genotypes as compared to the 10 susceptible genotypes, at 30, 45 and 60 days after sowing (DAS). TSS content was significantly- positively correlated with the incidence of thrips at 30th, 45th, 60th DAS and pooled mean of these 3 observations. SND incidence was significantlypositively correlated with the TSS content at 45th, 60th DAS and pooled mean. However, at 30th DAS this relationship was positive, but not significant. The total soluble protein content was lower in the 10 resistant genotypes as compared to the 10 susceptible genotypes, at 30, 45 and 60 DAS. Total soluble protein content was positively correlated (but non-significant) with thrips incidence at 45th and 60th DAS, but at 30th DAS it was significantly- positively correlated with thrips incidence. The pooled mean was negatively correlated with thrips incidence, but this relationship was non-significant. Similarly, the SND incidence was positively correlated with the protein content at 45th and 60 DAS and the pooled mean of 3 observations, but these correlations were non significant. However, at 30 DAS the relationship between SND and total soluble protein content was negative, but non significant. The total phenol content was higher in the 10 resistant genotypes as compared to the 10 susceptible genotypes, at 30, 45 and 60 DAS. The total phenol content was negatively correlated with thrips incidence at 45th, 60th DAS and pooled mean. However, at 30th DAS, this relationship was positively correlated but it was non-significant. Similarly, SND incidence was significantly, negatively correlated with the total phenol content at 45th and 60 DAS and the pooled mean. However, at 30 DAS this relationship was negative and non-significant Squared Euclidean distance dendrogram revealed a molecular diversity of 20 genotypes, wherein the cluster divided into two groups, the first group had 5 SND resistant genotypes (KBSH-53, KBSH-53A, GMU-676, GMU-664 and GMU-650) and the second had 15 genotypes with 14% dissimilarity. RAPD analysis, by using 5 random primers resulted in 28 different polymorphic levels, with maximum number of level of bands generated by the primer OPA-3.ennullThesis