Identification of high-yielding and stable Egyptian soybean genotypes for breeding across varied environments

This study evaluated the phenotypic stability of five Egyptian soybean genotypes (Giza 111, Giza 22, and lines 105, 127, and 129) across six environments comprising three water regimes of irrigation levels of 100% (normal), 75% (moderate drought), and 50% (severe drought) of field capacity, evaluated over two growing seasons (2023 and 2024). Morpho-developmental traits (germination percentage, days to flowering and maturity, plant height, hair number, defoliation percentage), yield components (branch number, seed size, pod number, empty pod number, 100-seed weight, seed yield per plant and feddan), and seed biochemical composition (protein and oil contents) were assessed. Morphological characterization revealed that Giza 22 and Line 101 exhibited superior germination rates, while Line 129 demonstrated maximum plant height and number of hairs. Giza 22 showed the earliest maturity date. For yield component analysis, Lines 127 and 129 achieved the highest seed yield, while Giza 22 displayed superior seed size and 100-seed weight, whereas Line 105 exhibited the lowest number of empty pods. The seed biochemical analysis demonstrated that Line 129 achieved maximum protein levels, whereas Line 105 attained the highest oil content. Furthermore, multi-trait stability assessment identified Giza 111 and Line 129 as phenotypically stable across multiple parameters, with Line 129 exhibiting optimal performance-stability equilibrium. This was corroborated by the weighted average of absolute scores from BLUPs (WAASB), where Line 129 recorded the lowest WAASB value, indicating superior multi-trait stability. Collectively, these findings suggest that Line 129 is a stable, high-yielding soybean genotype suited to variable conditions, including drought, making it a valuable resource for improving yield and stability in water-limited environments in Egypt. Further research should investigate the molecular and physiological traits behind its performance and the potential of Giza 111 in breeding for drought tolerance.