Investigating the water deficit stress tolerance in a segregating population of bread wheat using genotype × trait biplot

IntroductionWater deficit compared to other abiotic stresses is the most important factor limiting the growth and production in all crops, especially wheat. Investigating the response of crop plants under stress conditions is the best way to produce drought-tolerant cultivars and improve yield under stress conditions. The challenge of breeding for drought stress tolerance in all crop plants, is to achieve a rapid screening method of genotypes and genetic improvement of yield under these difficult environmental conditions. The objective of this experiment was to identify high-yielding and water deficit tolerant genotypes in an F4 generation population of bread wheat.Materials and methodsThe plant materials of this experiment were 90 genotypes of the F4 generation resulting from a cross between two bread wheat cultivars (Arta, a spring cultivar sensitive to salinity and drought stresses, and Arg, a tolerant cultivar to salinity and drought stresses). These genotypes along with the parents, were evaluated in split plots based on randomized complete block design with three replications under two conditions (normal irrigation and non-irrigation from the pollination stage) in the research farm of Faculty of Agriculture, Tabriz University, Tabriz, Iran, in 2014. Evaluating the genotypes were done by simultaneous application of stress tolerance index (STI) based on yield-related traits including grain yield (STI-Y), spike weight (STI-S), 1000-grain weight (STI-1000) and harvest index (STI-HI) and identifying the relationship between these indices using genotype × trait biplot analysis. The studied genotypes were ranked based on the relationships in the biplot, and the high yield and water deficit tolerant genotypes were identified.Research findingsThe results of biplot showed that the first two principal components explained 72% (46% and 26%, respectively) of total variance in the studied population. Acute and closed angle between the STI-Y, STI-S and STI-HI vectors indicated a positive correlation between these traits, while the open and obtuse angle between the STI-Y and STI-HI traits with STI-1000 showed a negative correlation between them. In contrast, an quadrant angle was observed between STI-S and STI-1000 vectors, indicating that these two traits were independent and uncorrelated. In total, according to the relationships in the biplot and based on the combination of STI-Y and STI-1000 vectors, genotypes No. 84, 45, 89 and 15 were identified and introduced as the highest grain yield and most water deficit tolerant genotypes.ConclusionThe results of this experiment led to identification of superior and promising genotypes with higher yield potential and more tolerance to water deficit stress. Genotypes No. 84, 45, 89 and 15, which were superior to the stress-tolerant parent, after the purification steps, can be introduced as suitable genotypes for cultivation under water stress conditions as well as in normal environments. These genotypes can be used as drought tolerant parental lines in future breeding programs.