Investigation of the correlation and causal relationships between grain yield and some important agronomic traits in corn lines under drought stress conditions

Objective
Corn is one of the most important cereal crops worldwide, playing a vital role in food security and various industries. However, drought stress and climate change are expected to impact agricultural production increasingly in the coming decades. Therefore, investigating the correlations and cause-effect relationships between corn grain yield and key agronomic traits under different drought stress conditions can help identify traits that most strongly influence grain yield and enhance the efficiency of corn breeding programs.
Materials and Methods
To study the relationships between grain yield per plant and agronomic traits, 40 advanced corn lines from the eighth generation (coded KSC704-S8-1 to KSC704-S8-40) were evaluated using a randomized complete block design with three replications under two different irrigation conditions.
Results
The combined analysis of variance for all studied traits revealed significant differences at the 1% probability level for both the effects of environment (moisture conditions) and line, indicating considerable variation among lines and between the two environments. Trait correlation analysis showed that grain yield per plant positively and significantly correlated with the number of grains per ear, hundred-grain weight, and grain width under both irrigation conditions. In stepwise regression analysis, when grain yield per plant was considered the dependent variable, the number of grains per ear, grain length, and number of ears per plant were sequentially included in the model under normal conditions. In contrast, the number of grains per ear and grain length were entered under drought stress conditions. In both cases, the models were significant at the 1% level. Path analysis further revealed that the number of grains per ear and grain length had the highest direct and positive effects on grain yield per plant under normal and drought stress conditions.
Conclusion
The findings indicate that the number of grains per ear, grain length, and ears per plant are the most important traits to consider as selection indicators for improving grain yield per plant in corn breeding programs.