Interspecific Hybridization for Enhancing Wilt Resistance in Cotton: A Genetic Approach Against Verticillium and Fusarium Wilts

Soil-borne pathogens, particularly Verticillium dahliae and Fusarium oxysporum f. sp. vasinfectum (FOV), represent a major constraint to global cotton (Gossypium spp.) production by inducing devastating wilt diseases. This study aimed to enhance cotton's resistance to these pathogens through intergenomic hybridization. Utilising elite cultivars (Gossypium hirsutum cv. Omad, G. barbadense cv. Termez-31) and the amphidiploid K-28, wild Gossypium germplasm (G. thurberi, G. raimondii) were introgressed into cultivated cotton to develop tetraploid (4×) and pentaploid (5×) hybrids. Resistance was evaluated through standardised inoculation under both controlled and field conditions (2022–2024). Key findings demonstrated that backcross progenies K-28 × Omad (O-117-125/18 and O-87-91/18) exhibited the highest resistance, with total infection rates of 10.5% and severe symptom rates of 2.5%–3.5%, significantly outperforming the control variety C-4727 (36.8% total infection). Notably, lines SP-1303 and T-1379 displayed broad-spectrum resistance against all five V. dahliae races, underscoring the efficacy of wild-species-derived resistance genes. The persistence of susceptibility in hybrids carrying the wilt-prone parent C-4727 (e.g., O-132-141/18: 29.5% infection) highlighted the crucial role of parental genotype selection. C-4727 is a high-yielding but Fusarium and Verticillium wilt-susceptible G. hirsutum cultivar, which has been widely used in breeding programs due to its agronomic potential despite its vulnerability to vascular wilt pathogens. Statistical analyses confirmed the dominance and heritability of resistance traits in introgressive lines, with low coefficients of variation (CV), which represent the ratio of the standard deviation to the mean (expressed as a percentage), ranging from 10.2% to 27.8%. This study establishes intergenomic hybridization as an effective breeding strategy for introgressing wilt resistance from wild Gossypium species into cultivated cotton. Resistant hybrids, particularly those incorporating the amphidiploid K-28, offer promising avenues for future breeding programs aimed at improving cotton's resilience against soil-borne pathogens.