Line × Tester Analysis Reveals Genetic Effects on Yield Components and Digital Seed Morphology in Spring Wheat (Triticum aestivum L.)

Wheat yield improvement requires a thorough understanding of the genetics underlying its component traits. This study investigated the combining ability and interrelationships of agronomic and seed morphological traits in bread wheat using a Line × Tester genetic design. Five lines (3011, 3012, 3013, CB-239, Aas-11) and three testers (99172, 8200, 3029) were crossed to generate 15 F1 hybrids. Parents and hybrids were evaluated in a randomized complete block design with three replications. Data on agronomic traits (e.g., plant height, seeds per spike, 1000-grain weight) and digital seed traits (e.g., area, perimeter, circulatory) extracted via SmartGrain software were subjected to analysis of variance, combining ability analysis, correlation, and principal component analysis. Significant genotypic differences were observed for all traits. Variance analysis revealed the importance of both additive and non-additive gene actions. Line L3 was identified as a superior general combiner for seeds per spike and seed size, while tester T1 was the best combiner for seeds per spike. A strong positive correlation was found between 1000-grain weight and seed circulatory, whereas a significant negative correlation was observed between seeds per spike and circulatory, indicating a physiological trade-off. The first five principal components explained 79.59% of the total variation. The results demonstrate the value of digital phenotyping and highlight specific parents as valuable genetic resources for breeding programs aiming to overcome yield trade-offs and develop high-yielding wheat varieties.