ROOT SYSTEM ARCHITECTURE AND PHYSIOLOGICAL TRAITS OF SOYBEAN GENOTYPES

Abstract

Soybean (Glycine max L.) is a major legume crop whose growth, productivity, and adaptability are strongly influenced by root architecture, physiological processes, and symbiotic efficiency. This study assessed the genetic variation of soybean varieties (Genetik-1, Sochilmas, Ehtiyoj, Xotira, Nafis) and breeding lines (Gen-8, Gen-9, Gen-19, Gen-26, Gen-40, BK-84, BK-98) across different developmental stages. Root morphological traits, nodule number, transpiration rate, and photosynthetic pigment content were evaluated under field conditions. The results revealed substantial genotypic differences. Among varieties, Ehtiyoj exhibited superior performance with the highest total root length (392.27 ± 90.68 cm) and root projection area (20.77 ± 2.51 cm²), indicating enhanced capacity for soil exploration. Genetik-1 also demonstrated total root length (364.07 ± 91.27 cm), while Sochilmas was distinguished by higher root volume (1.28 ± 0.14 cm³). In contrast, Nafis consistently displayed the lowest root development. Among breeding lines, Gen-8 and Gen-9 recorded the strongest root system development, while Gen-40 exhibited maximum root volume (1.51 ± 0.85 cm³). In terms of nodulation, Gen-26, Gen-8, and Gen-19 maintained high nodule numbers during reproductive stages, while traditional varieties showed limited persistence. Transpiration rate demonstrated that Gen-9, Gen-8, and BK-84 maintained higher water-use activity during vegetative and flowering stages, whereas Genetik-1 and Gen-19 showed reduced rates. Sochilmas, Nafis, Gen-19, and Gen-26 accumulated higher chlorophylls and carotenoids, contributing to superior photosynthetic efficiency. Overall, the findings confirm significant genetic variation among soybean genotypes. Breeding lines, particularly Gen-26, Gen-19, Gen-8, and Gen-9, exhibit enhanced traits for nitrogen fixation, water-use efficiency, and photosynthetic productivity, underscoring their potential in developing climate-resilient soybean cultivars.