Seed Germination, Viability, and Growth Dynamics of Intra-and Interspecific Hybrid Cotton Plants under Gamma Irradiation

The combined application of induced mutagenesis and hybridization is an effective approach for expanding genetic variability in cotton breeding; however, the interaction between gamma irradiation and hybrid performance remains insufficiently understood.In this study, dry seeds of the cotton (Gossypium hirsutum L.) analyzer line L-70 were exposed to 400 Gy gamma irradiation using a ^60Co source.The resulting M₁ plants were used as female parents in crosses with donor lines L-39, L-37, L-34, and L-35, as well as commercial cultivars Surkhan-108 and Surkhan-103.Seed germination, plant viability, plant height, and internode number were evaluated under field conditions using a randomized complete block design with three replications, and the data were analyzed using ANOVA (p < 0.05).Gamma irradiation significantly reduced seed germination (71.42% to 40.00%), plant viability (65.08% to 37.62%), plant height (91.44 to 79.12 cm), and internode number in the M₁ generation, confirming its inhibitory effect on early growth and development.The performance of F₁ hybrids was strongly genotype-dependent.The hybrid F₁ L-35 × M₁L-70 exhibited the highest germination (80.00%) and viability (75.24%), indicating a pronounced heterotic effect, while F₁ L-39 × M₁L-70 showed superior vegetative growth, reaching 101.25 cm at maturity and exceeding its parental line by 11.08 cm.In contrast, hybrids involving L-34 and L-37 displayed substantial reductions in germination, viability, plant height, and internode number, suggesting unfavorable allelic interactions and hybrid depression.The observed variation among hybrid combinations reflects the involvement of additive, dominance, and epistatic gene effects in the inheritance of these quantitative traits.Overall, the results demonstrate that the integration of gamma-induced mutagenesis and hybridization generates considerable phenotypic variability in cotton and can facilitate the identification of superior breeding materials.In particular, the combinations L-39 × M₁L-70 and L-35 × M₁L-70 were identified as promising genetic resources for the development of high-performing cotton cultivars with improved agronomic potential.

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