Genetic Analysis Of Performance Of Early Maize Inbred Lines Under Low-N and Striga-Infested Environments.

Breeding maize (Zea mays L.) hybrids for resistance/tolerance to Striga and low soil nitrogen (low-N) will reduce grain yield losses due to stresses in West Africa. Studies were conducted to determine the combining ability of IITA and CIMMYT inbreds and their performance in hybrid combinations under low-N and Striga-infested environments. One hundred and fifty hybrids derived from 30 inbreds using North Carolina Design II plus six checks were evaluated under low-N in Mokwa and Ile-Ife and Striga infestation in Abuja and Mokwa, Nigeria in 2011 and 2012. General combining ability (GCA) and specific combining ability (SCA) mean squares were significant for  yield and most other traits in Striga-infested and low-N environments, indicating that additive and non-additive gene action controlled these traits under each research environment. The GCA were higher than SCA for yield (68%), Striga damage at 8 (79%) and 10 (77%) weeks after planting (WAP), and number of emerged Striga plants at 8 (64%) and 10 (60%) WAP under Striga-infested environments, indicating that additive gene action controlled the inheritance of Striga resistance. The superior GCA_f for days to silking and GCA_m for ears per plant indicated that maternal and paternal effects modified the traits under Striga infestation but not under low-N environments. Inbred ENT 11 and TZEI 135 were identified as best tester under Striga infestation and TZEI 142 and TZEI 175 under low-N environments. Yield ranged from 775 kg ha^-1 for TZEI 168 x TZEI 54 to 4735 kg ha^-1 for ENT 11 x ENT 12 when Striga-infested and 1254 kg ha^-1 for TZEI 173 x TZEI 175 to 5541 kg ha^-1 for ENT 16 x TZEI 32 under low-N environments. Hybrid ENT 11 x TZEI 4 was the highest yielding and most stable across environments and should be commercialized to contribute to food security in the subregion.