Inheritance of sweetpotato resistance to sweetpotato weevils (C. brunneus and C. puncticollis)

Abstract

Sweetpotato weevils can cause up to 100% yield losses especially in hot and dry weather conditions. Use of resistant cultivars is the most sustainable strategy to control sweetpotato weevils. The requisite knowledge on inheritance pattern and gene action of field-based resistance to sweetpotato weevils needed to breed for resistance is unavailable. This study determined the inheritance pattern and gene action of field-based resistance to sweetpotato weevils. Eight parental clones varying in resistance to sweetpotato weevils were crossed in a half diallel mating design at the National Crops Resources Research Institute (NaCRRI). Due to high level of cross incompatibility and poor germination of seeds, only 27 families were generated. Performance of the diallel population (202 F1 genotypes) and eight parents for resistance to sweetpotato weevils, storage root yield (RYTHA) and dry matter (DM) content was assessed. Trials were conducted at NaCRRI, NaSARRI and Abi-ZARDI in 2017B and 2018A seasons. Significant differences were recorded in families, genotypes, family by environment interactions and genotype by environment interactions for WED1, RYTHA and DM. Sweetpotato weevil resistant genotypes with high yields and high dry matter content existed in the population studied. Diversity within families were higher than between families for resistance to sweetpotato weevils, yield and dry matter content. therefore, resistance to sweetpotato weevils, yield and dry matter content were genotype dependent rather than family dependent and with contribution from environmental factors. Therefore, selections for population improvement should be based on the performance of individual genotypes rather than families. Baker’s ratio (BR), narrow sense coefficient of genetic determination (NS-CGD) and broad sense coefficient of genetic determination (BS-CGD) were 0.46, 0.28 and 0.13, respectively. General combining ability (GCA) and specific combing ability did not significantly interact with environments. sweetpotato weevil resistance is moderately heritable and controlled by strong non additive gene actions. Rapid genetic gains for resistance to sweetpotato weevils could be accomplished by having many parent cross combinations. Parental genotypes “Anyina”, “Osapat”, “Tedelokerene”, and “New Kawogo” had favorable GCA effects and several specific favorable SCA effects for resistance to weevils; hence are promising parents to be used in population improvement for resistance to sweetpotato weevils.