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Theses

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2019 - 201912020 - 20231
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Subject: Genetics and Plant Breeding × Author: Choudhary, Raju Ram × End date: 2023 ×
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    ThesisItemOpen Access
    Population structure and genetic diversity studies for terminal heat stress tolerance in Indian mustard “[Brassica juncea (L.) Czern & Coss.]
    (CCSHAU, Hisar, 2023-02-03) Choudhary, Raju Ram; Ram Avtar
    Indian mustard is one of the most important oilseed crops and contributes more than 30% to the Indian vegetable oil pool. Heat stress is one of the major yield-limiting factors under changing climate conditions. Its impact is most severe at the reproductive stage, resulting in low seed yield. Therefore, assessment of genetic diversity, population structure, and molecular marker-traits associated with terminal heat stress tolerance in Indian mustard germplasm is necessary to accelerate the breeding effort. In the present study, a set of advanced breeding lines and genetic stocks representing 154 genotypes of Indian mustard were phenotyped for various morpho-physiological traits under control and terminal heat stress conditions. Besides, these genotypes were genotyped using 237 SSR markers. The results of the present study revealed significant effects of year, sowing date, and genotypes on various morpho-physiological traits under investigation. For the majority of the traits studied, high heritability and genetic advance were estimated. Trait association results revealed that seed yield/plant was significantly and positively correlated with plant height, number of primary branches/plant, number of secondary branches/plant, main shoot length, number of siliquae on the main shoot, siliqua length, number of seeds/siliqua, 1000-seed weight, photosynthetic rate, stomatal conductance, total chlorophyll content, and carotenoid content. DNA was isolated from all 154 genotypes by the standard method and subjected to SSR marker analysis. Out of total of 237 SSR markers, 111 were polymorphic. PIC values for all polymorphic SSR markers ranged from 0.013 to 0.627, with an average PIC value of 0.31. Unweighted Neighbor Joining-based dendrogram and population structure analysis divided the 154 genotypes into three clusters and two sub-populations, respectively. A total of 29 SSRs under timely sown and 33 SSRs under late sown environment were found to be associated with morphological and physiological traits by the MLM (Q + K) method. Chromosome B06 harbored the maximum number of SSRs (12), followed by chromosomes A08 (11) and A07 (five SSRs). Under terminal heat conditions, a total of 20 SSRs were specifically detected that were not associated under normal sown conditions. This meant that these particular genomic regions and QTLs were linked under extreme heat conditions. Overall, the heat-tolerant genotypes identified in this study and the SSR markers associated with terminal heat stress tolerance attributes will be helpful for the development of a heat-tolerant cultivar of Indian mustard through marker-assisted selection.
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    ThesisItemOpen Access
    Heterosis studies based upon Mori CMS system in Brassica juncea (L.)
    (CCSHAU, 2019) Choudhary, Raju Ram; Sheoran, R.K.
    Line x tester analysis was carried out to estimate heterosis and combining ability effects of 50 hybrids developed by crossing 10 Mori CMS lines with five restorer testers of Brassica juncea (L.). The F1 hybrids along with parental genotypes planted at Oilseeds Research Area, Department of Genetics & Plant Breeding, CCS Haryana Agricultural University, Hisar India during 2018-19 were evaluated for twelve characters, including days to 50 % flowering, days to maturity, plant height (cm), number of primary branches per plant, number of secondary branches per plant, main shoot length (cm), number of siliquae on main shoot, siliqua length (cm), number of seeds per siliqua, 1000-seed weight (g), oil content (%) and seed yield per plant (g). Analysis of variance revealed sufficient genetic variability among lines, testers crosses and line x tester for most of the traits. Presence of both additive and non-additive gene actions with preponderance of non-additive gene action in controlling yield and most of component traits so hybrid breeding would be the most appropriate breeding methodology. Four lines, namely, MA-8812, MA-9301, MA-8701 and MA-023 and one tester, MR-38 were found the good general combiners possessing highly significant positive GCA effects for seed yield per plant and component traits. Crosses MA-9301 x MR-44 and MA-9705 x MR-31 were showed significant SCA effects for seed yield per plant in desirable direction. Only two crosses namely MA-9301 x MR-44 and MA-8701 x MR-38 showed significant economic heterosis over standard check DMH-1. These crosses may be considered as most promising for further exploitation in breeding programmes and the parents involved may be converted to well adapted cytoplasmic male sterile or restorer lines.