Combining ability for resistance to Turcicum leaf Blight in maize under highlands of Uganda

Abstract

Maize (Zea mays L.) production in the highland areas of Uganda is constrained by high prevalence of Turcicum leaf blight (caused by Exserohilum turcicum) hence the need to breed for resistance to this disease. Gene actions governing TLB has been studied in lowland and mid-altitude maize but no study has been done for the highland agro-ecologies of Uganda. This study was conducted to determine the general (GCA) and specific (SCA) combining ability of selected maize inbred lines and F1 hybrids with resistance to TLB. Eighteen single- cross hybrids and three checks were evaluated following an Alpha Lattice design with two replications in three highland agro-ecologies of Uganda namely: Bulegeni, Rwebitaba and Kalengyere. Results indicated high significant (P≤0.001) differences among test environments for grain yield, plant height, ear height, 50% days to anthesis and 50% days to silking, an indication that environments were distinct. The GCA and SCA effects were significant (P ≤ 0.001) for most traits, indicating the importance of both additive and non-additive gene effects. Genotypes CKMARS10022, CKL14546, AMH704-43, AMH703-35, AMH704-51, AMH10142-29, AMH10142-10, CKMARS10022 x CKDHL120671, CKLTI0028 x AMH704-43, CKLTI0028 x AMH703-35, CKLT10028 x AMH10142- 29, CKLTI0028 x AMH10142-10 and CKL14546 x CKDHL120671 showed negative SCA effects for TLB indicating their resistance for TLB. Genotypes which possessed negative combining ability are recommended for TLB breeding.