Combining ability analysis of yield and resistance to late blight disease caused by Phytophthora infestans in Uganda

Abstract

Breeding for resistance to late blight disease caused by Phytophthora infestans (Mont.) de Bary in potato is the most economically, effective and ecologically sustainable method to control the disease and boost productivity. The study estimated combining ability effects of yield, yield related traits, late blight resistance and gene action controlling resistance to Phytophthora infestans. Eighteen F1 families generated from two sets of 12 parents, using a North Carolina Design II, were evaluated for relative area under disease progress curve (rAUDPC), yield and yield related traits in two late blight hotspot locations of Kachwekano and Kalengyere research stations. Trials were established using an alpha lattice design (6 x 5) with two replications. Both additive and non-additive genetic effects were important in controlling yield and late blight resistance. However, additive gene action was dominant. The general combining ability (GCA) to specific combining ability ratio (SCA); (GCA/SCA) for total tuber weight and late blight resistance was 0.53 and 0.62 respectively. Broad-sense heritability estimates were 0.78 for total tuber weight and 0.68 for relative area under disease progress curve (rAUDPC). This study showed some evidence of maternal effects for rAUDPC (1.45) and average tuber weight (ATW) (1.56), although these were not significant at P<0.05. Parents Kinigi, 392657.8, 396034.103, 396038.107, 395011.2, NKRK19.17, NKRN59.58 and 395017.14 had good GCA effects for both late blight resistance and yield related traits. Crosses of 392657.8 x 395017.14 and 396038.107 x NKRN59.58 had the highest SCA effects for yield related traits, while families Kinigi x NKRK19.17and 392657.8 x NKRN59.41 had the lowest SCA effects for rAUDPC. The relatively high heritability estimates and predominant additive genetic effects imply that genetic advances in resistance to Phytophthora infestans and tuber yield among these genotypes can be realized by selecting superior clones.