Genotype Stability Index for Root Yield and Tolerance to Sweetpotato Weevil Cylas puncticolis: A Tool for Identifying Climate Smart Varieties

Abstract

Abstract Despite the ability of sweetpotato to grow in marginal areas, large differential genotypic responses have been reported under varying environmental conditions. Differences in pest and disease pressure contribute significantly to inconsistencies in performance of genotypes in various environments. Using a randomized complete block design, eight sweetpotato genotypes were evaluated in one location successively for five years (seasons) (2010-2015). Additive main effects and multiplicative interaction (AMMI) stability value (ASV) was used to identify best genotypes that combine stability with high resistance to sweetpotato weevil Cylas puncticolis and root yield across the five seasons (years). Stability of genotypes for weevil infestation and damage thereof, and fresh storage root yield were determined for each season. The data on each of these parameters were correlated with rainfall and temperature data for each and across five seasons. Results show variability in the ranking of genotypes’ stability for resistance to weevil infestation and associated damage. Significant negative correlation was recorded between total rainfall and sweetpotato weevil damage. However, AMMI analysis of variance indicates genotype main effects, environmental main effects and the interaction thereof were all significant for root yield and weevil damage. Genotype selection index assisted to identify at least three genotypes namely Kokota, Lunga, and Kalungwishi which combined stability for high root yield and tolerance to weevil damage.