Molecular Characterization of Variability for Drought Tolerance in Wheat (Triticum aestivum L. em. Thell)

One hundred six F₂ plants taken from the cross between DBW-17 (drought susceptible) and WH-1080 (drought tolerant) were evaluated for various morphological and yield (days to heading, days to anthesis, days to maturity, plant height, effective tillers/plant, grains/spike, 1000-grain weight, grain yield/plant, biomass/plant and harvest index) and drought related traits (coleoptile length, chlorophyll content and chlorophyll fluorescence) under drought condition at Research Area of wheat section, Department of Genetics and Plant Breeding, CCS Haryana Agricultural University, Hisar, India. The segregating F₂ populations displayed large variation for days to heading (90-102), days to anthesis (91-104), days to maturity (122-129), plant height (43-87cm), effective tillers/plant (4-20), grains/spike (10-87), 1000-grain weight (26.09-47.50g), grain yield/plant (7.53-32.81g), biomass/plant (20.50-89.00g), harvest index (30.22-50.82), coleoptile length (2.40-4.60cm), chlorophyll content SPAD (32.96-61.85) and chlorophyll fluorescence (Fv/Fm) (0.542-0.798). Two of the DBW-17 x WH-1080 F₂ plants, had exceptionally higher chlorophyll content (55.05 and 52.65), chlorophyll fluorescence (0.798 and 0.737) and coleoptile length (4.60 and 4.50). Transgressive segregation for coleoptile length, chlorophyll content and chlorophyll fluorescence was noticed in F₂ populations. Grain yield showed significant positive correlation with effective tillers/plant, grains/spike, biomass/plant and harvest index and significant negative correlation with days to heading and days to anthesis in F₂ populations indicating the feasibility of improving grain yield. A total of 85 SSR markers were used to screen parental genotypes, out of these 20 primers showed polymorphism in banding pattern. Database of SSRs was generated using 20 primers and SSRs amplification were scored visually based on presence or absence of the band. A total of 42 alleles were detected in 106 F₂ plants and one new recombinant allele (different from those present in parents) was detected, number of alleles per locus ranged from 1-3 with an average of 2.10 alleles per locus. NTSYS-pc based two dimensional PCA analysis showed scattering of the F₂ population between the two distinct parental genotypes. Genetic similarity analysis showed that parental genotypes were quite distinct from each other. The cluster analysis led to distribution of parents and their F₂ populations in to eight groups at the similarity coefficient value of 0.56. In the cross DBW-17 x WH-1080 the dendrogram constructed and clustered in eight major groups. The hierarchical cluster analysis revealed that the F₂populations along with their parents were mainly divided into two major clusters and sixteen subgroups. Major cluster I, included drought susceptible parent DBW-17 and major cluster II had tolerant drought parent WH1080. Similar finding were also revealed by PCA analysis.

*Email: rpsaharan@hau.ernet.in & rajsaharan7@gmail.com