Evaluation of sweet potato genotypes for drought tolerance in the central zone of Tanzania

Drought is the most significant factor restricting crop growth and productivity in most agricultural fields of the world. The purpose of this study was to identify sweet potato genotypes tolerant for drought that could be used in breeding programs for improving sweet potato production in Tanzania. A field experiment involving 17 sweet potato genotypes was conducted at the Agriculture Research Institute (ARI) Hombolo, Dodoma between April and September 2012 (dry season). The experiment was laid out in a randomized complete block design (RCBD) with three replications. The genotypes were evaluated under well watered (WW) and water stress (WS) conditions where moisture level was maintained at field capacity until 60 days after planting (DAP). In the WW plots, supplementary irrigation was applied up to maturity at two days interval to maintain moisture level at field capacity while for WS irrigation was stopped at 60 DAP. Data was collected on yield, morphological parameters and level of antioxidant activity (catalase and peroxidase) and analyzed by GENSTAT, 13th Edition. Under WS conditions, the highest yield observed was 2.8 t ha-1 compared to 15 t ha-1 for WW. The study revealed that WS caused yield reduction of up to 97%. The five genotypes performed better under WS were SPKBH06/216, Simama, D12-02, SPKBH01/264 and Polista. On morphological parameters, the study revealed a reduction in plant size under WS. The level of antioxidant enzyme activities catalase and peroxidase showed to be higher under WS. Implying accumulation of reactive oxygen species. Thus such high levels could be used as an indicator for drought tolerant genotypes in sweet potato. From farmer’s participatory evaluation for culinary characteristics it was revealed that genotypes Polista, Simama, Pipi and SPKBH06/216 were the most preferred in terms of root taste, color and dry matter. The above genotypes could be used as breeding materials.Commission for Science and Technology (COSTECH) and SIDA-SARE