Line x tester analysis across locations and years in Sudanese x exotic lines of forage sorghum

Combining ability in forage sorghum [Sorghum bicolor (L.) Moench] was not as much investigated as in grain sorghum. In the present study, 4 local stocks (Testers) and 7 exotic stocks in A3 cytoplasm were crossed in line x tester fashion to investigate combining ability in forage sorghum. The hybrids and their parents were evaluated across two years (2002 2003) and at two locations in Khartoum State, Sudan. Forage yield, days to flower, plant height, leaf to stem ratio and stem diameter were studied. Significant general (GCA) and specific combining ability (SCA) effects in desirable direction were detected for most traits. The best general combiners for forage yield and earliness in flowering were identified. Both additive and non-additive gene actions were important in the expression of all characters with the preponderance of additive actions for days to flower, forage yield, stem diameter, leaf to stem ratio and non-additive actions for plant height. GCA effects were more stable over years than specific ones. Selection in early generations was suggested for characters predominately controlled by additive genes. Heterosis breeding was recommended for forage yield improvement. For leaf to stem ratio, selection must be based on more genetically diverse materials.