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African dry and starchy (DS) orange-fleshed sweetpotato [Ipomoea batatas (L.) Lam] (OFSP) cultivars, distinct from American moist or medium dry and sweet OFSP, have potential to fight vitamin A deficiency (VAD) in the world. This study assessed the genotype X environment (G X E) interactions in multienvironment trials (METs), the genetic correlations for total root yield (TYLD), biomass (BIOM), harvest index (HI), root dry matter (RDM), root starch (RST), root sucrose (RSU), root β-carotene, (RBC), root Fe (RFE), root Zn (RZN), root Ca (RCA), and root Mg (RMG) and the potential contributions of the cultivars to fight VAD and mineral deficiencies. Nine DS OFSP cultivars, (Ejumula, Zambezi, Carrot_C, Kakamega, KMI61, Abuket_1, SPK004/6/6, SPK004/6 and Naspot_5/50) and a medium dry and sweet OFSP cultivar (Resisto) were tested in METs in Uganda. The components were smaller than σ2G components for HI, RDM, RST, RSU, and RBC, making it possible to ably select for the traits in the early stages. The σ2GXE components were larger than σ2G components for TYLD and mineral traits. Thus, like yield, breeding for mineral traits in sweetpotato is complex, requiring prior data on the causes of the G X E interactions. Medium to high positive correlations among mineral traits favor parallel selection, and it merits further study to efficiently improve the mineral trait complex by an index. Clearly, a 50- to 100-g ration of all the cultivars, except Naspot_5/50, can provide 100% recommended dietary allowance of vitamin A for a 5- to 8-yr-old child. [ABSTRACT FROM AUTHOR]

Alternaria leaf petiole and stem blight is an economically important disease of sweet potato ( Ipomoea batatus L.) in tropical and sub-tropical environments. Published research on cultivar resistance to the sweet potato disease is limited. To evaluate cultivar reaction and stability to the disease, multi-location and replicated experiments were established in 12 environments in Uganda. Disease severity (area under disease progress curves – AUDPC), and cultivar root yield were also assessed. Significant differences (P < 0.001) in AUDPC were detected among cultivars. Mean AUDPC ranged from 46.3 (Araka Red) to 78.4 (New Kawogo) across locations and seasons and the genotypes Araka Red and Tanzania had the lowest disease values. The location and season effects accounted for 67.1% and 7.5% of the total variance of AUDPC recorded among cultivars. The ranking of cultivars based on predicted AUDPC from Additive Main Effect and Multiplicative Interactive model (AMMI) showed that the NASPOT 1, the susceptible check, and New Kawogo were most susceptible to the disease in 11 of the 12 environments. Low and stable disease was consistently recorded and predicted on NASPOT 3 and the landrace cultivars Tanzania, Dimbuca, and Araka Red across environments. These results suggest that landrace cultivars had relative stability to the disease and wide adaptation across environments. These results suggest that AMMI statistical model and other multivariate techniques can be utilized for prediction of Alternaria disease stability in these locations. [ABSTRACT FROM AUTHOR]