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T HREE SWEETPOTATO cultivars, Abees, Mogamba and Santo Amaro, were subjected to moderate (-0.5MPa) and severe drought stress (-2.5MPa) or to salt treatments up to 200mM NaCl, respectively. Patterns of leaf polyamine contents were analyzed to verify whether these metabolites could be used as early traits of tolerance. Physiological parameters like leaf relative water content, total chlorophyll content, leaf electron conductance, stomata resistance and transpiration rate were used to indicate stress conditions of the plants and growth parameters were applied to identify the level of tolerance among the used cultivars. In all three cultivars, drought led to an increase of putrescine (Put) and decrease of spermidine (Spd) concentrations while spermine (Spm) was decreased only in the Santo Amaro cultivar. The most tolerant cultivar was Mogamba followed by Santo Amaro and Abees. However, this descending order was not reflected by the specific changes in polyamine levels but it is altered under drought as well as under salinity in both sensitive and tolerant cultivars. More investigations are needed to figure out if polyamines behave as a response of stress and/or a protective mechanism.

This investigation was carried out to evaluate the chemical characteristics of new eight sweet potato varieties namely, CEMSA 74-228, SANTO AMARA, NC 1525 and KEMB 37 (creamy flesh) and JAPON TRESMESINO, LO 323, TAINUNG 64 and BEAUREGARD (yellow flesh), and study their suitability for processing. The obtained results reveal that SANTO AMARA and KEMB37 varieties were the best ones having the highest content of chemical constituents compared with those of the other studied creamy flesh sweet potato varieties. Moreover, 140 days from planting was the best harvesting time that achieved the highest chemical characteristics. All selected creamy sweet potato varieties had adequate minerals contents especially, KEMB 37 followed by NC 1525 and CEMSA 74-228 then SANTO AMARA varieties that could be considered good sources of minerals for human nutrition. Yellow flesh sweet potatoes have been recognized as valuable sources of carbohydrates, protein, dietary fibers and could be considered as good sources of both vitamin C and total carotenoids. Moreover, TAINUNG 64 and LO 323 were found to be good sources of βcarotene (pro-vitamin A). The more suitable harvesting time for yellow sweet potato varieties, which recorded the highest levels of essential elements, was 140 days from planting. On the other hand, TAINUNG 64 variety could be considered the best one compared to the other examined varities. The most suitable varieties that having good quality attributes for processing were SANTO AMARA and KEMB 37 as creamy flesh and TAINUNG 64 and BEAUREGARD as yellow flesh sweet potato varieties. Moreover, these varieties could be successfully used in the production of new and untraditional sweet potato products.