The correlation and combining ability of sole maize and maize-haricot bean intercropping were investigated through field experiments conducted at Bako and Hawasa in a Mid altitude Agro-ecology of Ethiopia to estimate combining ability of the inbred lines under sole maize and maize-haricot bean intercrop and to assess the correlation between traits under the two cropping systems. The results showed that general combining ability (GCA) and specific combining ability (SCA) for grain yield (GY) was highly significant under sole maize and bean intercrop. The results suggested that additive and non-additive gene actions were important in the inheritance of GY under the two cropping conditions. The rest of traits were governed by additive gene effect, except, anthesis date and plant height under intercrop inherited by additive gene action. Lines, L10 and L15 were the best combination for GY under sole and had reasonably good GY under bean intercrop. while, L9 and L17 were good combination for GY under maize intercropped. Crosses involving L9 and L17 had good GY under intercrop. Under intercropped, L14 x T1 and L20 x T1 had the highest SCA for GY. The correlation between sole maize and bean intercrop for each trait was significant and positive.

Keywords: General combining ability; Grain yield; Specific combining ability; Standard heterosis