Principal component and path analysis of agro-morphological traits of Kabuli chickpea genotypes (Cicer arietinum L.) under dryland spring-planting and autumn-planting

Legumes are the most economically important food source for humans due to their protein richness, especially in developing and underdeveloped countries. Chickpea yield in spring-planting under dryland cropping decreases due to increasing temperature and day length and the occurrence of end-season drought and exposure to important pest's activity. In autumn-planting, early flowering, escaping from pests and optimal use of annual rainfall help to significantly increase in grain yield. Increasing the growth period during autumn planting has been found to result in taller plant height, making mechanical harvesting more feasible. The success of a plant breeding program relies on implementing a suitable selection design that takes into account both correlated and non-correlated relationships. Recently, a significant positive correlation has been observed between grain yield and several traits such as the number of pods, number of seeds, 100-kernel weight, and harvest index in chickpea. These traits were also found to have a direct and significant effect on chickpea grain yield. Additionally, there was a high direct effect observed for pod number, number of seeds, 100-kernel weight, and single-seed weight on chickpea grain yield.

This research was conducted on 112 chickpea genotypes in dryland spring-planting (non-cold stress condition) and autumn-planting (cold stress) based on augmented design in Dryland Agricultural Research Institute located in Maragheh. Total pods number, number of empty pods, number of tow-seed pods, plant height, first pod height from soil level, number of pods with one seed, days to maturity initiation, days to 90% maturity, 100-kernel weight, pod diameter, pod length, biomass, harvest index, fertility percent and single-plant yield were meassured. The correlation analysis, stepwise regression and path analysis, and principal component analysis were used for identifying the relationships among agro-morphological traits.

In autumn-planting condition grain yield positively correlated with all traits except days to 90% maturity, but in spring-planting condition the correlation between grain yield and first pod height, days to maturity initiation, days to 90% maturity, 100-kernel weight, pod diameter and pod length were not significant. In spring-planting, 100-kernel weight and total pods number were negatively correlated. In both spring and autumn-planting, the 100-kernel weight showed a significant positive correlation with pod diameter and pod length. This indicates that genotypes with larger pods also tend to have larger seeds. Furthermore, in autumn-planting, there was a significant positive correlation between pod diameter, pod length, and grain yield. However, these correlations were not significant in spring-planting. Stepwise regression analysis was performed to assess the factors influencing grain yield in both planting conditions. In spring-planting, the number of total pods, 100-kernel weight, fertility percent, and the number of two-seed pods were found to have direct and significant effects on grain yield. On the other hand, in autumn-planting, the number of total pods, pod length, number of empty pods, 100-kernel weight, and the number of two-seed pods were included in the final model as predictors of grain yield. These results suggest that these factors play a crucial role in determining grain yield in their respective planting conditions. In spring-planting, the genotypes 108, 63, 65 and 99 had the highest number of total pods, number of single pods, biomass and plant yield and genotypes 55, 76, 81, 82, 84, 85 and 88 had the highest weight of 100-kernel, pod length and pod diameter. In autumn-planting, the genotypes 87 and 22 had higher biomass and grain yield, genotypes 45 and 65 had higher total pods and number of single pods, genotype 89 had higher total pods and biomass and genotype 94 had higher total pods, number of single pods, biomass and yield.

Correlation analysis results showed that in non cold stress condition (spring-planting), due to the short growth period, the significant relationship of most important agronomic traits with grain yield were not revealed and important components such as 100-kernel weight did not have enough opportunity to significantly affect grain yield. In spring-planting, total pods number had a high direct effect and correlation coefficient with grain yield, but the indirect effect of this trait through 100-kernel weight on grain yield was negative because increasing the number of total pods causes decreasing the kernel weight. In autumn-planting, despite the high direct effect of total pods number on grain yield, due to the indirect negative effect through the number of empty pods, the correlation coefficient of total pod number with grain yield was not very high. Finally in order to increase grain yield in chickpea genotypes in breeding programs it is recommended that under cold stress and non-stress conditions, selection should be based on the number of total pods per plant, which is a visible trait and easy to measure.