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

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)(2011)(2012)(2013)(2014)(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.

Adaptation of sweet potato [Ipomoea batatas) (L.) Lam] genotypes in various agro-ecological zones of Malawi

“…This finding concurs with those of Chalwe et al (2017) whose study on sweet potato genotypes in Zambia showed significant AMMI analysis variance of genotype, environment and their interactions on root yield and weevil damage. Gedif and Yigzaw (2014) and Daba et al (2015) observed similar significant environment, genotype and genotype × environment interactions influence on yield of potato (S. tuberosum L.) and sesame, respectively, in Ethiopia (p≤0.01).…”

“…It is not uncommon for stability studies to recommend one or two genotypes from a test of many genotypes. Chalwe et al (2017) and Makunde et al (2017) both identified two out of eight and 48 genotypes respectively as most stable for root yield and weevil damage and root yield and drought tolerance, respectively. In a study done on winter wheat genotypes in Turkey, two were also reported as stable for all environments by Altay (2012).…”

“…GEI refers Tanzania bred, came through Kenya Semusa CIP, Nairobi to differential sensitivity of genotype performance from one environment to another (Chalwe et al, 2017). While modern plant breeders work to improve various attributes of crops ranging from pest and disease resistance to biofortification, yield improvement has remained the main drive for most breeding programs (Yahaya et al, 2015).…”

“…Sweet potato [Ipomoea batatas) (L.) Lam], like other crops suffers yield losses that are due to abiotic and biotics limitations (Tekalign, 2007;Kivuva et al, 2014;Chalwe et al, 2017) hence an understanding of the nature and magnitude of GEI among sweet potato genotypes is essential in both sweet potato breeding and variety release (Singh et al, 2006;Rukundo et al, 2013). From time in memorial, genotypic yield levels have been the focus of many sweet potato farmers but adaptation to environments and stability (consistency of yield) of the genotypes have always been the underpinning determinants of final yields (Eberhart and Russell, 1966;Bilbro and Ray, 1976;Rea and Vieira, 2002).…”

Selection of superior genotype of sweet-potato in Indonesia based on stability and adaptability

“…Some well-known methods include regression, additive main effect and multiplicative interaction (AMMI) and Genotype plus Genotype × Environment (GGE) Biplot methods (Finlay and Wilkinson, 1963;Yan et al, 2007;Hongyu et al, 2014). Several researchers also performed stability and adaptability evaluations by combining several test methods (Adebola et al, 2013;Kivuva et al, 2014;Chalwe et al, 2017). The AMMI and GGE biplot analysis are important methods in analyzing GEI that assist plant breeders to identify and select the superior genotypes in certain environments (Adebola et al, 2013;Amare et al, 2014;Kivuva et al, 2014).…”