Yield Performance, Combining Ability and Stability of Early- to Medium-Maturing Doubled-Haploid Maize Lines in Eastern Africa.

Maize is a staple food crop in sub-Saharan Africa, where increasing productivity is essential for food security. This study assessed testcross performance and combining ability of early- to medium-maturity doubled haploid (DH) maize lines adapted to eastern Africa. A total of 732 testcross hybrids derived from 244 DH lines crossed with six testers, along with six commercial checks, were evaluated across eight locations. Agronomic and disease-related traits were recorded and analysed using mixed models, line × tester analysis and stability tools (AMMI and GGE biplots). Significant genetic variation (p ≤ 0.05) was detected among genotypes, environments and their interactions. Additive genetic effects were predominant, as indicated by high Baker's ratios (> 0.70) and narrow-sense heritability estimates (0.71-0.95), highlighting the importance of general combining ability (GCA) in hybrid prediction. Several lines, including CKDHL141370, CKDHL142389 and CKDHL143580, exhibited favourable GCA effects for grain yield and earliness, while also contributing to resistance against turcicum leaf blight and grey leaf spot. The top-performing hybrids, such as (CKDHL120312/CML312)//CKDHL142124, CKDHL143094 and CKDHL142908, yielded 7.4-8.2 t ha-1, representing a 29%-79% advantage over commercial checks. GGE biplot analysis explained 71.27% of the variation and identified several hybrids combined high yield with stability across environments. Overall, these results demonstrate that integrating line × tester and GGE biplot approaches is highly effective for identifying superior parental lines and predicting their hybrid performance. The identified superior hybrids warrant further validation in on-farm trials for potential commercialization to enhance maize productivity and resilience in sub-Saharan Africa.