Alternaria blight (Alternaria spp.) is an important sweetpotato disease in Uganda causing yield losses of over 50 % in susceptible genotypes. In Uganda, Alternaria bataticola and Alternaria alternata are the major species with A. bataticola the more aggressive of the two. The most effective control measure for this disease is the use of resistant genotypes. This study was conducted to determine the inheritance of resistance to Alternaria blight and the general and specific combining abilities of the available germplasm. Sixteen parental clones varying in reaction to Alternaria blight were crossed using the North Carolina II mating scheme. Due to incompatibility of some parents, two sets of compatible parents were formed. Differences among the families for Alternaria blight severity were significant while general combining ability (GCA) and specific combining ability (SCA) mean squares were highly significant (P < 0.001) for the disease with GCA sum of squares (SS) being more predominant at 67.4 % of the treatment SS for Set 1 and the SCA SS predominant at 54.0 % of the treatment SS for Set 2. This indicated that both additive and non-additive effects are important in controlling this trait. Some parents with high, negative GCA effects produced families with undesirable SCA effects and the reverse was also true. This implies that the best parents should not be chosen on GCA alone but also on SCA of their best crosses. The wide range in the area under disease progress curve for the families indicated that it was possible to select for highly resistant genotypes.
Genetic analysis of resistance to Alternaria leaf petiole and stem blight of sweetpotato in Uganda
Sseruwu G., P. Shanahan, R. Melis, G. Ssemakula. 2016. Genetic analysis ofresistance to Alternaria leaf petiole and stem blight of sweetpotato in Uganda. Euphytica210(3):393-404 DOI 10.1007/s10681-016-1703-5