Tolerance diversity in Kabuli chickpea local germplasm ‬‏under terminal drought

Chickpea is mainly grown in the west and north west of Iran in dryland conditions, and in most areas, it is planted as post rainy season crop from March to late May. Due to irregular, untimely and insufficient rainfall in cultivated areas, this plant is usually suffering from drought during flowering and pod filling stages, which are the most susceptible stages of chickpea growth. Utilization of local genetic diversity that are useful sources of adaptation gene to environmental changes is a starting point and a functional approach to overcome this problem. Assuming the local chickpea accession conserved in National Plant Gene Bank of Iran (NPGBI) have appropriate diversity for terminal drought tolerance, a research was conducted with the aim of identify drought tolerant accessions and determining their yield potential under dryland condition.

Seventy Kabuli chickpea landraces were identified as tolerant accessions in different previous projects were done in NPGBI entered to this study. The experiment was held in Sanandaj and Karaj research station both in two different treatments. Control and drought treatments, through cutting off irrigation at flowering stage till maturity, in Karaj and dryland and complementary irrigation treatments, using two additional irrigations during flowering and pod filling, in Sanandaj station. The accessions were planted in the second half of March in augmented design, during 2016-17 growing season. Different agronomical traits were recorded, quantitative drought tolerance and susceptibility indices, were calculated and based of them accessions were grouped using the principle component and cluster analysis.

 Based on the results, a significant decrease in day to maturity, flowering period, canopy height and width, plant weight, pods number and weight per plant, seeds number per plant, plant yield, biomass, yield and harvest index were observed in drought stress conditions. There was considerable variation in yield and yield components, biomass and harvest index, among understudied landraces. Seed production increased by 9.7 and 1.3 times under irrigation treatment in Karaj and Sanandaj, respectively.Principal component analysis across tolerant and susceptible indices and considering eigen values greater than or equal to 1.0 showed that in both locations, two components together accounted for 92.32 and 99.33 percent of variation. The first component contributed most of the variability 52.18% in Karaj and 83.62% in Sanandaj was explained by variation in HM, STI, GMP and MP indices. The second component was explained by the diversity among genotypes for TOL and SSI indices. Hence, accession number KC.215172, KC.215286, KC215369 and KC.216010 in Sanandaj station and accession number KC.215286, KC.215727, KC215442, KC.215443, and KC.216023 in Karaj with higher amount of GMP and STI indices and lower amount of TOL and SSI were among more drought tolerance accessions.Cluster analysis based on evaluated traits and calculated drought tolerance and susceptibility indices, were divided accessions in to 3 clusters in Karaj. The cluster number three that TOl and SSI indices and the percentage of unfilled pods had lower values than the total average and plant weight, seed and pod number per plant, seed and pod weight per plant, biomass, yield, harvest index and STI and GMP indices have higher values than the average was called drought tolerant cluster. Accessions number KC.215727, KC.215442, KC.215710, KC.216023 were this cluster member.  The cluster number 4 that had high yield potential and high STI and GMP indices and including 24 accessions was drought tolerant cluster in Sanandaj. Accession number KC215369 was in this group.

Although it is possible to increase the yield of chickpea by changing the planting season from traditional spring planting to winter, but farmers still prefer spring planting. Therefore, it is necessary to produce suitable high-yielding cultivars for both seasons, because in this way, farmers have the opportunity to choose suitable cultivars for spring or winter planting, depending on their local environmental or climatic conditions. The mismatch between grouping of tolerant genetic accessions in two experimental locations was due to the lack of similarity of stress intensities between two locations. The intensity of stress was 0.89 in Karaj and 0.24 in Sanandaj and this issue affects the reaction of the accessions. Genotype × environment interaction is the most important challenge in breeding program. Therefore, description of interaction effects and finding out appropriate genotypes with specific or common adaptation for target environments is the most important aim for multi-year and multi-location assessments. Summarizing the results of both sites demonstrated accessions number KC.215286, KC.215442 and KC.215443 were superior genotypes at both locations.Totally, this study revealed the existence of desirable diversity in terms of agronomic traits and stress tolerance among local accessions of chickpea and highlighted the importance of paying attention to these accessions for advanced and complementary research to identify potentials of these valuable heritage.