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ThesisItem Open Access Introgression of mosaic resistance in popular short duration cassava varieties of Kerala through marker assisted selection(Deparment of Plant Breeding and Genetics, College of Agriculture, Vellayani, 2018) Darshan, S; KAU; Arya, KThe present study entitled “Introgression of mosaic disease resistance in to popular short duration cassava varieties of Kerala through marker assisted breeding”was conducted in the Department of Plant Breeding and Genetics, College of Agriculture, Vellayani, Kerala Agricultural University and Division of Crop Improvement, ICAR- Central Tuber Crops research Institute, Sreekariyam, Thiruvananthapuram, Kerala during the period 2014 - 2017 with the core objective of introgression of cassava mosaic disease (CMD) resistance to short duration varieties of cassava through marker assisted selection (MAS) and to study the inheritance of early bulking nature. The research work was carried out as four experiments. In the first experiment, Five early bulking high yielding lines viz, Sree Jaya, Sree Vijaya, Vellayani Hraswa, CI 889 and 9S 75 and three testers viz, CR 54A3, IMS2-5 and CI 273 with resistance to cassava mosaic disease were selected and planted in a pollination block and crossed in Line x Tester (LxT) design to produce hybrid seeds of 15 F1 combinations. Experiment II was conducted in two parts. Screening of F1 seedlings for CMD resistance and early bulking nature was carried out in the first part of experiment II, where hybrids along with the parents were evaluated. Analysis of variance revealed significant differences among the genotypes for all the traits studied. All the agronomic traits were recorded and inheritance of early bulking and its correlation with other traits were studied. The CMD incidence expressed significant and negative correlation with tuber yield per plant where as significant and positive correlation for all other traits with tuber yield per plant was observed among the F1’s. As a part of experiment II (b), seedlings without the CMD visual symptoms were subjected to multiplex PCR and the results revealed that among the parents Sree Jaya, Sree Vijaya, Vellayani Hraswa expressed presence of Srilankan Cassava mosaic Virus (SLCMV) and Vellayani Hraswa expressed the presence of both SLCMV and Indian Cassava mosaic Virus (ICMV). Among the crosses, Sree Jaya x CR54 A3 (L1x T1), Sree Jaya x IMS2-5 (L1xT2), Vellayani Hraswa x IMS2-5 (L3xT2), CI 889 x CI 273 (L4xT3) expressed the presence of SLCMV. Real time PCR (qPCR) assay for seedlings identified CI 889 (L4), 9S 75(L5), CR 54A3 (T1), IMS2-5 (T2) and CI 273(T3) among the parents and Sree Jaya x CR54 A3 (L1x T1), Sree Jaya x IMS2-5 (L1xT2), Sree Jaya x CI 273(L1x T3) and 9S 75 x CR54 A3 (L5x T1), 9S 75 x IMS2-5 (L5xT2) and 9S 75 x CI 273 (L5x T3) among the crosses as highly resistant, based on viral load present in the DNA sample. Based on the previous report ten CMD resistance linked markers were screened through BSA and five of which SSRY 28, SSRY 44 SSRY 40, SSRY 106 and SSRY 235 were selected. Among the CMD linked SSR markers studied, the maximum polymorphism was elucidated by SSRY 28, SSRY 44 and followed by SSRY 235. SSRY 28 is a strongly linked marker to CMD2 which is a dominant gene conferring resistance among the clones of combinations (L1xT1, L2xT2, L3xT1 and L3xT3) three of five markers revealed alleles associated with CMD2 gene In the third experiment to evaluate the early bulking clones, field was laid out in randomized block design (RBD) with three replications consisting of CMD resistant clones along with parental clones using miniset technique. Analysis of variance revealed significant differences among the genotypes for all the traits. Measurement of heterosis was carried out considering parent Vellayani Hraswa (L3) as check and results revealed that standard heterosis was positive and significant in the combinations Sree Jaya x CR 54A3 (L1xT1) and Sree Jaya x CI 273 (L1xT3) for all the yield contributing traits. The crosses Sree Jaya x CR54 A3 (L1x T1) and Sree Jaya x CI 273 (L1xT3) exhibited negative standard heterosis for CMD. Combining ability analysis showed significant gca, sca variances and gca, sca effects for all the traits. Moreover gca/sca variance ratio indicated preponderance of dominance / non-additive gene action for the inheritance of all traits. Among the lines, Sree Jaya (L1) exhibited positive and significant gcaeffect for tuber yield and yield contributing traits. Among the testers, IMS2-5 (T2) exhibited negative and significant gca effect for CMD. Among the crosses Sree Jaya x CR54 A3 (L1x T1) exhibited positive and significant scaeffect for girth of tuber and stem girth, 9S 75 x CI 273 (L5xT3) exhibited positive and significant scaeffect for tuber yield per plant, CI 889 x CR 54A3 (L4xT1) exhibited negative and significant scaeffect for CMD. In the last experiment, through bulk segregants analysis using 5 SSR markers linked to early bulking in cassava were selected out of 9 SSR markers selected. Among 5 SSR markers of CMD and early bulking nature two SSR markers (SSRY 28 and SSRY 106) associated with resistance to CMD and One SSR marker, ESTs (SSRY) 292 associated to early bulking nature has been identified. Among the crosses, clones from Sree Jaya x CR54 A3 (L1xT1), Sree Jaya x CI 273 (L1x T3) and 9S 75 x CR 54A3 (L5xT1) are being confirmed with CMD resistance as well as early bulking nature.ThesisItem Open Access Heterosis and combining ability analysis to leaf curl virus in chilli(Department of Plant Breeding and Genetics, College of Agriculture, Vellayani, 2014) Darshan, S; KAU; Seeja, GAn experiment on “Heterosis and combining ability analysis to leaf curl virus in chilli” was carried out in the Department of Plant Breeding and Genetics, College of Agriculture, Vellayani, Kerala Agricultural University during the period 2012-2014 to identify the best general combiners and specific combiners for developing superior cross combinations, the inheritance pattern of yield, yield attributes and qualitative traits and resistance to leaf curl virus disease. Six parents viz, Ujwala, Anugraha, Vellayani Athulya, Jwalasakhi, Pant C1 and Pusa Sadabahar were crossed in a diallel pattern and the resultant 30 hybrids were evaluated in full diallel fashion. The field experiment was laid out in randomized block design (RBD) with three replications. Analysis of variance revealed significant differences among the genotypes for all the traits. Measurement of heterosis was carried out considering parent Ujwala (P1) as check and results revealed that standard heterosis was positive and significant in the combinations, Vellayani Athulya x Pusa Sadabahar (P3 x P6), Pusa Sadabahar x Vellayani Athulya (P6 x P3), Pusa Sadabahar x Jwalasakhi (P6 x P4) and Vellayani Athulya x Jwalasakhi (P3 x P4) for all the traits. The crosses, Vellayani Athulya x Pusa Sadabahar (P3 x P6), Pusa Sadabahar x Ujwala (P6 x P1), Jwalasakhi x Pusa Sadabahar (P4 x P6) were exhibited positive and significant standard heterosis for yield and yield related traits. The cross Pant C1 x Vellayani Athulya (P5 x P3) exhibited negative and significant standard heterosis for incidence of leaf curl virus disease. Combining ability analysis showed significant gca, sca , rca variances and gca, sca effects for all the traits. Moreover gca/sca variance ratio indicated preponderance of dominance / non-additive gene action for the inheritance of all traits. Among parents, Pusa Sadabahar exhibited positive and significant gca effect for plant height, branches per plant, number of fruits per plant, yield per plot, total soluble protein, total carbohydrate, poly phenol oxidase, vitamin C, oleoresin and negative and significant effect for incidence of leaf curl virus disease. Among crosses, Vellayani Athulya x Pusa Sadabhar (P3 x P6) exhibited positive and significant sca effect for fruit weight and yield per plot whereas; Ujwala x Vellayani Athulya (P1 x P3) exhibited negative and significant sca effect for leaf curl virus disease incidence. Among the biochemical parameters studied, membrane integrity in terms of % leakage had positive association with LCV disease. Total soluble protein content, phenol content, total CHO content, poly phenol oxidase, vitamin C and oleoresin had negative association with LCV disease. Artificial screening was carried out in insect proof cage to confirm the resistance/tolerance to leaf curl virus disease among the superior crosses identified in the field experiment. Crosses Vellayani Athulya x Pusa Sadabahar (P3 x P6) and Pant C1 x Vellayani Athulya (P5 x P3) were exhibited tolerance for leaf curl disease incidence. From the present study Vellayani Athulya x Pusa Sadabahar (P3 x P6), Pusa Sadabahar x Vellayani Athulya (P6 x P3) and Pant C1 x Vellayani Athulya (P5 x P3) were identified as superior crosses and these can be used for improving yield and quality trait like resistance to leaf curl virus disease in future breeding programme.