The use of untapped plant genetic resources of wheat (Triticum spp.) can enhance its productivity. In the present study, we characterized 22,416 accessions of three different species of wheat conserved in the Indian National Genebank using 23 qualitative and 12 quantitative traits to develop a core set. These accessions were highly diverse on the basis of range, coefficient of variation, and Shannon–Weaver diversity index. Initial grouping was done on the bases of species and origin, and thereafter, agromorphological data were used to develop core sets for each species group using the heuristic approach with PowerCore. Finally, a composite core set was constituted comprising 2,226 accessions, which included 1,779 accessions of bread wheat (T. aestivum L.), 394 of durum wheat [T. turgidum L. subsp. durum (Desf.) van Slageren], and 53 of emmer wheat [T. dicoccon Schrank; syn. T. turgidum L. subsp. dicoccon (Schrank) Thell]. The core set was validated under field conditions. Also, the coincidence rate of range (CR) (bread wheat, 85.78%; durum wheat, 87.52%; and emmer wheat, 95.34%) and variable rate of the coefficient of variation (VR) (bread wheat, 174.9%; durum wheat, 136.5%; and emmer wheat, 105.81%) were more than the threshold values of 80 and 100%, respectively. The phenotypic correlations among different traits attributable to coadapted gene complexes and total variation shown by principal components in the entire set were also mostly preserved in the core set. The composite wheat core and the trait‐specific germplasm sets identified would serve as valuable resources for global wheat improvement programs.

Plant genetic resources, the source of genetic diversity provides a broad genetic foundation for plant breeding and genetic research, however, large germplasm resources are difficult to preserve, evaluate and use. Construction of core and mini core collections is an efficient method for managing genetic resources and undertaking intensive surveys of natural variation, including the phenotyping of complex traits and genotyping of DNA polymorphisms allowing more efficient utilization of genetic resources. A mega characterization and evaluation programme of the entire cultivated gene pool of wheat conserved in the National Genebank, India was undertaken. Wheat accessions with limited seed quantity, were multiplied in the off-season nursery at IARI Regional Station, Wellington during rainy season 2011 and the entire set of 22,469 wheat accessions were characterized and evaluated at CCS HAU, Hisar, Haryana during winter season 2011-12 for 34 characters including 22 highly heritable qualitative, and 12 quantitative parameters. The core sets were developed using PowerCore Software with stepwise approach and grouping method and validated using Shannon-Diversity Index and summary statistics. Based on Shannon-Diversity index, PowerCore with stepwise approach was found better than PowerCore with grouping. The core set included 2,208 accessions comprising 1,770 T. aestivum, 386 T. durum, and 52 T. dicoccum accessions as a representative of the total diversity recorded in the wheat germplasm. The core set developed will be further validated at different agro-climatic conditions and will be utilized for development of mini core set to enhance the utilization by wheat researchers and development of climate resilient improved varieties.

The experiment was conducted with 60 genotypes of bread wheat. These genotypes were grown in RBD using three replications during Rabi 2016-17 at Research Area of Wheat and Barley Section, Department of Genetics and Plant Breeding, CCS HAU, Hisar. To study the variability, correlation and path analysis, data were recorded for yield and its component traits i.e. days to 50% heading, days to anthesis, grain growth rate at 14, 21, 28 days (mg/g/day), plant height (cm), number of effective tillers/meter, flag leaf length (cm), flag leaf width (cm), flag leaf area (cm2), spike length (cm), number of spikelets per spike, number of grains per spike, 1000 grain weight (g), grain yield per plot (g), biological yield/plot (g) and harvest index (%). ANOVA showed highly significant differences among the genotypes for all the traits indicating adequacy of material and the traits studied for further assessment of genetic variability parameters. High value of GCV and PCV was recorded for grain yield per plot, followed by biological yield, indicating greater amount of variability among the genotypes. Highest heritability was recorded for days to 50% heading, followed by days to anthesis. Highly significant and positive association was perceived between grain yield and tillers per meter, plant height, number of grains per spike, number of spikelets per spike, flag leaf area, grain growth rate at 14, 21 and 28 days after anthesis, spike length, 1000 grain weight, biological yield and harvest index. The high direct effects were recorded for biological yield, harvest index, flag leaf breadth, number of effective tillers per meter and 1000 grain weight, in order.

Wheat grain yield is limited due to terminal heat stress. Inconsistency of the previous results reflects the interactions between genotypes and environments. In North West Plain Zone (NWPZ), where the hot, dry wind is frequent during grain filling, wheat cultivars suffer from loss of grain weight because of low grain filling rate. A field study was carried out under late sown conditions in NWPZ to evaluate the phenological variations using heataccumulated system and its relation with yield in twenty five wheat genotypes. Grain yield was positively correlated with days to heading, biological yield, harvest index and grain number per spike in both timely (TS) and late sown (LS) varieties, while grain weight and flag leaf area also showed positive correlation with grain yield in LS varieties. Grain growth rate (GGR) at 14 and 28 days after anthesis (DAA) showed positive correlations with grain weight in TS, and in LS genotypes flag leaf area was positively correlated with GGR at 14 DAA. Increasing days to heading resulted in higher grain yield, while increasing grain filling duration has little effect. PBW 343 and WH 711 in TS varieties and WH 1022 and PBW 373 in LS group had highest grain yields in their respective groups among the genotypes studied. These genotypes tended to have relatively longer pre-heading periods with medium maturity. The results of this study indicate that NWPZ adapted cultivars would have long pre-heading periods, moderate grain filling duration, high grain filling rates and mature early to avoid late-season drought and high-temperature stresses to attain high yields. Therefore, high yielding wheat cultivars adapted to subtropical environments can be develop by selecting the genotypes with medium maturity and a relatively long time to heading.

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