Diallel analysis of turcicum leaf blight resistance and grain yield in maize and its implications for genetic improvement

A half-diallel mating design involving nine diverse maize genotypes was employed to investigate combining ability for resistance to Turcicum leaf blight (TLB) and for grain yield performance under both artificial inoculation and natural infection at two hotspot locations in India. Analysis of variance (ANOVA) revealed significant differences among parents and crosses for all studied traits, indicating substantial genetic variability. Diallel analysis revealed significant general combining ability (GCA) and specific combining ability (SCA) effects for disease-related traits as well as yield, highlighting the role of both additive and non-additive gene actions. Additive effects were predominant for TLB resistance, whereas non-additive effects mainly governed yield under both artificially inoculated and natural infected conditions. GCA effects identified P ₁ , P ₂ , P ₃ , P ₅ and P ₉ as key donors of additive alleles conferring TLB resistance, while P ₂ , P ₃ , and P ₅ consistently showed positive GCA effects for both disease resistance and grain yield across both disease conditions. Among the hybrids, P ₃ × P ₇ showed strong positive SCA effects for grain yield along with significant negative SCA effects for disease resistance. Other promising crosses, including P ₁ × P ₅ , P ₄ × P ₆ , P ₅ × P ₆ , P ₂ × P ₄ , P ₅ × P ₇ and P ₄ × P ₉ , also combined favorable SCA effects for grain yield and disease resistance. Hence, integrating GCA and SCA analyses could provide an effective strategy for identifying superior parental lines and hybrids, supporting the development of TLB-resistant, high-yielding maize cultivars. To check for stability and adaptability, these promising combinations should be validated through multi-location evaluation.