Abstract
ABSTRACT White Guinea yam (Dioscorea rotundata Poir.) is an important tuber crop grown extensively in tropical regions of West African yam belt. Tuber yield, dry matter content, and tolerance to yam mosaic virus are key traits used for identification and selection of superior varieties for commercial deployment. In this study, we estimated genetic parameters for fresh tuber yield, tuber dry matter content, and quantitative field tolerance to yam mosaic virus in 49 clones grown in multi-environment trials (METs). We conducted genomic prediction involving 6337 single nucleotide polymorphisms (SNPs) and phenotypic field evaluation of data collected on the three traits from four sites. Additive genetic and non-genetic factors contributed significantly to phenotypic variation of studied yam traits in METs but to varying degrees. The non-genetic effects were relatively high for most of the measured traits. Narrow-sense heritability values were low (<0.30) for all studied traits. Further analysis of the performance of the clones at test sites with additive main effects and multiplicative interaction (AMMI) analysis exhibited significant genotype by environment interactions (GEI) for the three traits. The AMMI identified TDr10/00412, TDr11/00055, and TDr09/00135 clones with lowest mean trait stability index and outstanding performance for fresh tuber yield (t ha−1), tuber dry matter, and mosaic virus resistance across sites. The elite clones identified could serve as useful source of alleles for the genetic improvement of the crop and possibly considered for release to farmers.
Highlights
Yam (Dioscorea spp.) is a vegetatively propagated crop comprising >600 species (Burkill 1960), of which 11 are widely cultivated for food and industrial applications globally
Plant materials included 49 white Guinea yam clones that were evaluated at four sites in Nigeria (Ibadan, Abuja, Ubiaja and Ikenne) in the 2017/2018 cropping season
Healthy tubers of each genotype were cut into setts of 200 g each, pre-treated with a mixture of 70 g Macozeb, 75 mL Chlorpyrifos and 10 L tap water for 5 min and dried for 20 h under shade to heal wounds and prevent rotting of cut surfaces of setts caused by pathogenic organisms
Summary
Yam (Dioscorea spp.) is a vegetatively propagated crop comprising >600 species (Burkill 1960), of which 11 are widely cultivated for food and industrial applications globally. The average fresh tuber yield of yam reportedly increased from 7.8 to 8.8 t ha−1, the production increment was attributable to corresponding increase in total production area from 1.2million ha in 1961 to 8.9million ha in 2019 (FAOSTAT 2020) This scenario is representative of the strong growth in sub-Saharan Africa (SSA) agricultural output that accrued mainly from area expansion and intensifica tion of cropping systems relative to large-scale improvement in productivity (Brink and Eva 2009; NEPAD 2014). These efforts resulted in a slow-paced increase in yield per hectare that did not match the rapid global population growth (Heerink 2005). Yam diseases, such as yam anthracnose and yam mosaic virus, cause severe yield losses and genetic erosion, and restrict international movement and exchange of germplasm (Egesi, Onyeka, and Asiedu 2007)
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