Abstract
AbstractSweetpotato is grown throughout the year in Mozambique but drought affects storage root yield and biomass productivity. The objectives of this research were to estimate the impact of genotype × environment interactions (G × E) in sweetpotato and select genotypes based on drought indices such as geometric mean, percent yield reduction, drought sensitivity index and harvest index. A total of 58 clones were evaluated during the dry season of 2006, 2008 and 2009. Two treatments were applied for this multi-year trial: full irrigation and without irrigation at the middle of root initiation growth stage. The field layout was a randomized complete block design with three replications. ‘Jonathan’, ‘Resisto’ and ‘Tanzania’ were the check cultivars in each treatment. Storage root and vine yields were recorded at harvest in the trials. Harvest index was computed from the yield data. The analysis of variance, regression and the additive main effects multiplicative interaction (AMMI) analyses, plus phenotypic coefficient of variation and ecovalence were used for dissecting the G × E and assessing the stability of each clone. Treatment, genotype × treatment and genotype × year (G × Y) interactions had highest contributions to the variation in storage root yield observed among clones. The stability of harvest index was significantly correlated with the absolute AMMI’s IPCA1 and IPCA2 values for storage root yield. Cultivar performance varied within treatments. Four clones had significantly higher storage root yield (t ha−1) than ‘Tanzania’, the best check cultivar under drought. In conclusion, storage root yield (t ha−1) was negatively affected by drought and G × Y interaction. Harvest index stability and the geometric mean may be key to identify clones with storage root yield stability and high storage root yield under both treatments. At least two environments should be used at early breeding stages to consider harvest index in the early breeding cycle.
Highlights
Sweetpotato provides household food security and is an important source of energy due to its ability to grow throughout the year in some areas of the sub-Saharan Africa, where it ranks among the most widely grown root crops (Andrade et al 2009)
Sweetpotato cultivars with high root yield and stability may be bred, when the heritability of harvest index is higher than that of storage root yield. Drought in these multi-year trials reduced significantly storage root yield by 25 %, which falls within the range (15–39 %), noticed previously after 20 consecutive days under this water deficit during the growing season (Gong and Wang 1990)
Water shortage suppresses plant growth—which can be measured as vine yield in sweetpotato– due to loss of turgor in expanded cells (Kirnak et al 2001)
Summary
Sweetpotato provides household food security and is an important source of energy due to its ability to grow throughout the year in some areas of the sub-Saharan Africa, where it ranks among the most widely grown root crops (Andrade et al 2009). Mozambique grew about 122,000 ha of sweetpotato with a harvest of 890,000 t of storage roots (FAO 2015). Sweetpotato production doubled in Mozambique due to promotion and dissemination of orange-fleshed (OFSP) cultivars with the aim of alleviating vitamin A deficiency in the diets, and replacing maize in areas affected by frequent flood (MICOA 2005) and drought. There are two growing seasons in Mozambique: rainy, humid, hot summer (October–March) and dry, cool winter season (May–July) near perennial rivers. The summer cultivation of sweetpotato is affected by the rainfall, which is often uneven, in southern Mozambique that is drier than the north of this country
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