Genetic Variation and Trait Associations of Grain Yield and Other Quantitative Traits for Identification of Promising Wheat (Triticum spp.) Accessions under Nitrogen Stress

Aims: Identification of superior genotypes combining high nitrogen use efficiency (NUE) and high grain yield under low nitrogen supply is imperative to the development of nitrogen use efficient wheat varieties for use by farmers in low input wheat production systems to combat the problem of nitrogen stress. The objectives of the study were to identify high yielding wheat genotypes under nitrogen stress and assess multiple morpho-physiological and yield related traits for their contribution and association to the adaptation of the accessions to nitrogen stress.

Methodology: This study assessed the response of 100 wheat accessions grown in an augmented randomized complete block design in 3 blocks under two contrasting nitrogen regimes: (1) Nitrogen stress (0 kg/ha N) and (2) recommended nitrogen supply (120 kg/ha N), in Dharwad, India during rabi 2014/2015.

Results: Significant genotypic responses were observed for most of the traits assessed in both treatments. Grain yield showed significant positive correlation with normalized difference vegetative index (NDVI), tillers per meter row, harvest index, biomass and NUE in both treatments. Several accessions showed adaptation to nitrogen stress by reducing their NDVI and total biomass production while increasing harvest index. Cluster analysis with Mahalanobis distance partitioned the accessions into four groups displaying high and significant inter-cluster distance, signifying that hybridization between nitrogen stress-adapted parents from the groups will produce the maximum genetic recombination for nitrogen stress tolerance in subsequent generations.

Conclusion: Accessions DDK 1025, HW 2004, HD 4709, HI 8592 and K 8020 with superior yields under nitrogen stress condition can be utilized as sources of tolerant genes in breeding programmes to improve yield performance under low nitrogen supply.