Replication Data for: Variance Component Estimations and Mega-environments for Sweetpotato Breeding in West-Africa

The current study was aimed at identifying mega-environments in Ghana and evaluating adaptability of superior sweetpotato genotypes from a targeted breeding effort. Three sets of genotypes were evaluated in multi-environment trials (MET). In the first part, twelve sweetpotato varieties were evaluated across nine environments representing the main agro-ecological zones in Ghana. Analysis of MET data was conducted using a stage-wise approach withthe genotype-by-environment (GxE) table of means used as a starting point to model the GxE interaction for sweetpotato yield. Emphasis was given to the genetic correlation matrix used in a second-order factor analytic model that accommodates heterogeneity of genetic variances across environments. A GGE plot of storage root yield explained 82 percent of the variation in the first principal component and visualized the genetic variances and discriminating power of each environment, and the genetic correlation between the environments. Two mega- environments, corresponding northern and southern trial sites, were delineated. In the second part of the study, six breeding lines selected from the south and eight breeding lines selected from the north were tested and compared to two common check clones at five locations in Ghana. A Finlay-Wilkinson stability analysis resulted in stable performances within the target mega-environment from which the genotypes were selected, but predominantly without adaptation to the other region. Our results provide a strong rationale for running separate programs to allow for faster genetic progress in each of these two major West African mega-environments by selecting for specific and broad adaptation.

本研究旨在鉴定加纳境内的巨环境区（mega-environments），并评估定向育种项目所获优异甘薯基因型的适应性。本研究通过多环境试验（multi-environment trials, MET）对三组基因型展开评价。第一部分试验中，在覆盖加纳主要农业生态区的9个试验环境下，对12个甘薯品种进行了评价。研究采用分阶段分析法对多环境试验数据进行解析，以基因型-环境互作（genotype-by-environment, GxE）均值表为起点，构建甘薯产量的GxE互作模型，本次分析重点关注二阶因子分析模型中使用的遗传相关矩阵，该模型可适配不同环境下遗传方差的异质性。块根产量的GGE双标图（GGE plot）可解释第一主成分82%的变异，能够直观呈现各环境的遗传方差与区分能力，以及环境间的遗传相关性。最终划定了两个分别对应北部和南部试验点的巨环境区。研究第二部分中，在加纳的5个试验点，对从南部筛选获得的6个育种品系以及从北部筛选获得的8个育种品系进行了测试，并与2个常用对照无性系进行对比。Finlay-Wilkinson稳定性分析结果显示，这些基因型在其来源的目标巨环境区内表现稳定，但基本无法适应另一区域。本研究结果为设立独立育种项目提供了充分依据：通过针对特异性和广适性开展选择，可在西非这两个主要巨环境区中各自实现更快的遗传进展。