Singh, Satish KumarKUMARI, MANISHA2024-09-232024-09-232023M/PBG/210/2021-22https://krishikosh.egranth.ac.in/handle/1/5810214834A study was conducted at the wheat breeding farm, RPCAU, Pusa, Samastipur, Bihar, in rabi season of 2022-23. The objective was to evaluate different bread wheat lines for their response to drought stress under restricted irrigation condition. The research encompassed a range of analyses including variation assessment, genetic advancement, correlations, path analysis, molecular characterisation, and diversity evaluation. In both environments i.e., optimum or normal and stress conditions, 30 distinct genotypes were investigated. Randomized Block Design with 3 replications was used for both conditions to evaluate better performing genotypes under respective environmental conditions. The analysis of variance for both (optimum and restricted irrigation) conditions revealed significant variations among all the studied lines of wheat genotypes. The traits such as root mass/ unit soil weight (RM), no. of grains per spike (NGPS), leaf thickness (LT) and 1000 grain weight (TGW) has high heritability and genetic advance in both conditions. Whereas, grain yield per plant (GY) has high heritability as well as genetic advance only under restricted irrigation condition. Grain yield per plant (GY) was observed significantly and positively correlated with no. of effective tillers / plant (NTPP), no. of grains per spike (NGPS), soil moisture (SM), spike neck diameter (ND), canopy cover (CC), relative water content (RWC), root mass per unit soil weight (RM), leaf thickness (LT) and 1000 grain weight (TGW) in both i.e., optimum and restricted irrigation conditions. Whereas, it was negatively correlated with plant height (PH), days to 50 % flowering (DF), days to maturity (DM), canopy temperature (CT) and soil temperature (ST) under both scenarios. GY was non- significantly negatively correlated with days to 50 % flowering in both conditions. Canopy temperature and soil temperature has negative correlation with no. of grains /spike. However, soil temperature is positively correlated with drought susceptible index (DSI). These results showed that CT, ST and DSI is related to yield lose under restricted irrigation scenario. The traits like no. of effective tillers per plant, no. of grains per spike, relative water content and thousand grain weight are of prime importance in the selection process of grain yield improvement programme, as they show significant and positive association with yield per plant. Under restricted irrigated condition, no. of effective tillers per plant, no. of grains per spike and relative water content has positive and direct effect on grain yield. Although, other characters also contributed to yield indirectly via these traits. All 30 bread wheat lines were classified into 5 and 4 clusters in optimum and restricted irrigation conditions respectively. In case of non-stressed condition, highest inter cluster distance was found between cluster I and cluster III, while lowest inter cluster distance was recorded between cluster III and cluster V. Under restricted irrigation condition, highest inter cluster distance was recorded between cluster I and cluster II, while lowest inter cluster distance was found between cluster I and cluster IV. Genotypes NEST 18-25, 8th HPYT 454, 12th HPYT 554 and TAW-123 can be selected as a suitable donor parent for traits such as no. of effective tillers per plant, no. of grains per spike, leaf thickness and 1000 grain weight under optimum irrigation condition. Whereas, genotypes like NEST 18-25, 12th HPYT 600, NEST 19-25 and 38 SAWSN 3231 can be selected as a suitable donor parent for traits like no. of effective tillers per plant, no. of grains per spike, root mass per unit soil weight, leaf thickness, 1000 grain weight and grain yield per plant under restricted irrigated condition. A set of 21character specific SSR markers were used for diversity analysis at molecular levels in the subjected wheat genotypes. These markers have clear, sharp and scorable bands for all the used wheat genotypes. Based on dendrogram analysis all the 30 genotypes were classified into 6 clusters among which cluster II contained maximum no. of genotypes whereas, cluster VI recorded as mono-genotypic cluster as it has only one genotype. High similarity coefficient was found between 12th HPYT 489 and 42 ESWYT 3108 followed by 11th HPYT 405 and 8th HPYT 454.EnglishThesis