Estimation of genetic diversity and grouping of double haploid barley lines in terms of photosynthetic partitioning in normal and water deficit conditions

Grain growth in wheat depends on current photosynthesis and stem water-soluble carbohydrates (WSC). In semiarid regions with terminal drought, grain filling in cereals may depend more on stem water-soluble carbohydrates content than on current assimilates. Reduction in grain yield under water deficit condition is attributed to shorter duration of linear grain growth despite increased contribution of stem reserves to grain yield. The amount of stem reserves is measured either by changes in stem dry weight (indirect method) or by stem water-soluble carbohydrates content (direct method). Genotypic variation in the rate and duration of linear grain growth and in percent contribution of stem reserves to grain yield has a little evaluated in cereals and especially in the barley.

The objectives of this study were estimation of genetic diversity and grouping of double haploid barley lines in terms of photosynthetic partitioning in normal and water deficit conditions. Plant materials used in this experiment, include 72 double haploid lines along with Steptoe and Morex parents on a research farm of Mahabad University were studied in a simple lattice design with two replications in normal conditions and water deficit conditions 2016. Irrigation in stress and non-stress treatments was done after 90 mm evaporation from class a pan, depending on the temperature and evapotranspiration until heading stage. In water deficit stress treatment, irrigation was stopped at heading stage. Measuring of understudy traits were done after anthesis stage. In present study leaf partitioning, steam partitioning, spike partitioning, spike to steam ratio, remobilization, remobilization portion in grain yield, thousand kernel white, biological yield, grain yield and harvest index was measured.

Results showed that there was a significant difference between studied genotypes for all traits. Under normal conditions, significant positive and negative segregations for all traits other than biological and in water deficit significant positive and negative segregations for all under study treats were observed, furthermore in both conditions, the highest amount of narrow-sense heritability was calculated for harvest index traits and grain yield. The results of regression analysis of traits affecting grain yield showed that under normal conditions, two traits of 1000 grain weight and remobilization of photosynthetic materials (R2 = 89) identified as The most effective traits on grain yield. Under water deficit conditions, the harvest index, the remobilization portion in grain yield and remobilization (R2 = 0.82) were identified as the most effective traits on grain yield. In normal irrigation conditions, two traits of 1000 grain weight and remobilization of photosynthetic materials had a positive and direct effect on grain yield. However, under water deficit conditions, the harvest index and remobilization had direct positive effect and remobilization portion in grain yield showed a negative and direct effect on grain yield. Based on the results of cluster analysis, genotypes were classified into two groups under normal and three groups in water deficit conditions.

In present study photosynthetic remobilization of photosynthetic materials had a positive effect on grain yield variation in both conditions. Therefore, selection of genotypes with the highest amount of photosynthesis accumulation and remobilization could be an effective way to increase grain yield in both conditions. Based on the results of cluster analysis in normal conditions, genotypes located in cluster 1 and under water stress conditions of genotypes located in cluster 2 due to had the highest allocation and remobilization of photosynthetic materials and grain yield are recommended.