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2014 - 20202
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Subject: Genetics and Plant Breeding × Author: Shruti × Start date: 2010 × Type: Thesis ×
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    Inheritance and mapping of Ascochyta blight resistance in chickpea (Cicer arietinum L.)
    (Punjab Agricultural University, Ludhiana, 2020) Shruti; Dhillon, S.K.
    To identify new sources of resistance to Ascochyta blight, a total of 100 genotypes including 9 checks were screened over a period of two years using field screening technique and cut-twig screening technique. Amongst these, 17 genotypes viz. FLIP 09294, GL 15007, GL 15010, GL 15011, GL 15012, GL 15014, GL 15016 GL 15019, GL 15020, GL 15021, GL 15031, GL 15032, GL 15033, GL 15036, GL 15043, GL 15044 and GL 15050 showed moderate resistance to Ascochyta blight during both the years of testing. Analysis of variance revealed significant differences amongst the 100 genotypes for almost all the yield and its attributing traits. On the basis of D2 analysis, these 100 genotypes including 9 checks were grouped into 11 clusters. Inter-cluster distance amongst these 11 clusters varied from 19.15 (cluster VII and cluster III) to 600.61 (cluster XI and IX) while intra-cluster distance varied from 0.00 (cluster IV and cluster IX) to 17.97 (cluster VIII). Harvest Index (56.46%), seed yield (8.59%), ascochyta blight score (6.28%), followed by biomass (5.03%), days to maturity (4.69%) and days to initiation of flowering (4.53%) contributed maximum towards genetic divergence. Selection for divergent parents based on these characters will be useful for developing potential hybrids and will increase the scope of isolating desirable recombinants in segregating generations. Concludingly, genotypes such as ICCV 15117, GL 15046, GL 15008, GL 15010, GL 15015, ICCV 15109, ICCV 15116 and ICCV 15311, FLIP 0962 will serve as suitable candidates for hybridisation or future breeding programmes. In order to understand the inheritance of Ascochyta blight resistance against the isolate 8 of race 6(3968) 5 F1s and 362 F2 plants derived from the cross PBG 7 x HC 5 were used and confirmation was done in F3 generation with pooled data. The study on genetics of resistance to Ascochyta blight in the cross PBG7 x HC 5 indicated dominance of susceptibility in F1, and segregation ratio of 15 (S): 1 (R) with χ2 value of 0.58 obtained in F2 indicated digenic recessive control to AB resistance in this cross. ddRAD-Seq of 75 RILs of this cross was undertaken to map the Ascochyta blight resistance in the cross PBG 7 x HC 5. A total of 2833 filtered polymorphic loci were used for linkage map construction through ddRAD-Seq. The maximum number of markers were mapped on CaLG04 (1227), while the minimum number of markers were on CaLG08 (75). One major QTL was identified for AB resistance on LG04 at 121 cM flanked by rs_NC_021163_1_3584639 and rs_NC_021163_1_7078480 at 115.97cM and 124.03 cM respectively. This QTL was characterised by high LOD (29.179) and high PVE% (29.66%). The SNP loci found to be linked with AB resistance in this study needs to be validated in different genetic background of other population to be used in marker-assisted selection.
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    ThesisItemOpen Access
    Phenotypic evaluation and molecular profiling of Brassica juncea (L.) lines carrying introgressions from Erucastrum abyssinicum
    (Punjab Agricultural University, Ludhiana, 2014) Shruti; Atri, Chhaya
    Introgression lines (ILs), created in Brassica juncea, following hybridization with Erucastrum abyssinicum were studied to catalogue their genetic diversity and crop performance under stressed ecologies. Molecular data generated following amplification with 72 SSR markers (35 (A genome) and 37 (B genome)) suggested the occurrence of high genetic diversity. ILs like JA-85, JA-128, JA-77, JA-30, JA-72, JA-96, JA-196, JA-95, JA-75 fell in Cluster 1 along with E. abyssinicum and were amongst those lines that carried a very large chunk of genomic information from the wild donor species. Graphical genotyping revealed that percent introgression varied from 12.5% to 40% with maximum introgression in JA-30, followed by other ILs like JA-85 (39.9%), JA- 53 (38.3%), JA-128 (37.4%), JA-75 (37.4%), JA-77 (36%), JA-96 (35.9%), JA-95 (35.1%), JA-72 (34.9%), JA-196 (34.1%), JA-245 (33.7%). Least introgression from the donor parent was recorded in JA-24 (12.5%). On the whole, maximum introgression was seen in chromosome 3 of ‘B’ genome which had 43.2 percent introgression from the donor parent. Morphological evaluation helped to identify useful ILs for earliness and components associated with crop productivity. Some of the ILs like JA-344 (number of primary branches), JA-92 (number of siliqua on main shoot), JA- 42 (siliqua length), JA-159 and JA-235 (seeds per pod), JA-192 (seed yield) performed equally well in both the environments. Grain yield was positively associated with flowering, plant height, leaf area index etc. which indicated that higher yield can be achieved by bringing changes in these parameters. GG Biplot analysis also confirmed a high level of variation for all the traits studied. Morphological data for test characters was also used to generate Euclidean distance graphs based on Mahalanobis D2 analysis and the ILs were clustered in 10 groups. The growing unpredictability of climate requires breeding of cultivars adapted to broad environments. Three ILs namely JA-59, JA-65, JA-240 were able to tolerate high temperature while 16 ILs viz. JA-22, JA-31, JA-35, JA-38, JA-45, JA-65, JA-127, JA-147, JA-149, JA-174, JA-193, JA-233, JA-331, JA-343, JA-352 and JA-36 could tolerate low temperature stress during flowering. These ILs can further be used in future breeding programmes suited for the development of varieties for stressed ecologies.