Abstract
Studies were conducted to determine tuber yield stability and adaptability of some elite yam (Dioscorea sp.) genotypes in northern Ghana. Ten elite exotic yam genotypes alongside one locally cultivated farmer-preferred variety, Laribako, were grown in five environments between 2010 and 2012. These 11 genotypes were arranged in a randomised complete block design with three replications and assessed for tuber yield and yield components. Analysis of variance indicated significant p < 0.05 genotypic variation for tuber yield and the yield components studied. Genotype × environment interaction effect was significant p < 0.05 for tuber yield and mean tuber weight but not significant p > 0.05 for number of tubers per mound. Apart from genotype 95/18922, all the exotic genotypes had significantly p < 0.05 higher tuber yields than the local check, Laribako. The highest tuber yield (16.03 t ha−1) across environments was obtained from 96/19158 followed by 95/00594 (14.9 t ha−1). According to the additive main effect multiplicative interaction (AMMI) analysis, genotype (G), environment (E), and GxE interaction, respectively, explained 39.71%, 36.03%, and 24.26% of the total sum of squares for tuber yield. For number of tubers per plant, GxE effect explained the greatest percentage (60.46%) of the total sum of squares compared to genotype effect (22.00%) and environment effect (17.54%). The local variety, Laribako, was more stable across all environments though low yielding compared to the exotic genotypes. Three genotypes, 95/19158, 95/19177, and 96/02025, were more stable across environments than the other exotic genotypes. Genotype 95/18544 was the most sensitive and for that matter responded positively in the favorable environments. The study identified genotypes with specific and general adaptation potential across different environments for tuber yield that can be further tested in on-farm trials for possible release.
Highlights
Yam (Dioscorea sp.) is among the oldest recorded food crops believed to have originated in tropical areas [1]. ough six economically important species (D. rotundata, D. alata, D. caryensis, D. esculenta, D. dometorum, and D. bulbifera) are grown as staple foods in Africa [2], D. rotundata is the most widely cultivated within the yam zones of West Africa
Nduwumuremyi et al [37] indicated that the presence of significant genotype × environment interaction effect for quantitative traits such as tuber yield can seriously limit the efforts made in selecting superior genotypes for different environments. is is because such performance cannot be replicated in environments with different growing conditions
Purchase et al [29] proposed a yield stability index that combines ranking based on high yield and stability into a single index, the yield stability index (YSI). e additive main effect multiplicative interaction (AMMI) analysis identifies specific genotypes which are stable across environments [20, 21]
Summary
Yam (Dioscorea sp.) is among the oldest recorded food crops believed to have originated in tropical areas [1]. ough six economically important species (D. rotundata, D. alata, D. caryensis, D. esculenta, D. dometorum, and D. bulbifera) are grown as staple foods in Africa [2], D. rotundata is the most widely cultivated within the yam zones of West Africa. Sub-Saharan Africa accounts for 70% of world yam production [3], and in Ghana, in particular, the crop is cultivated in 34 out of the 43 agriculturally important districts in the Guinea savannah zone in the north, savannah transition zones in the middle belt and forest zones as well as the costal savannah zones in the south [4]. Yam is a vital crop for Ghana’s domestic market and to the international market as well.
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