Physiological Functions of Chilling Tolerant Sweetpotato (Ipomoea batatas L.) Genotypes

An experiment was conducted in the greenhouse to select genotypes tolerant to chilling injury from lines of a genetically diverse population. Seventy nine sweetpotato F1 breeding lines from three major variety crosses including ‘Vardaman’, ‘Jewel’, and MD-708’ were tested for tolerance to chilling injury. Genotype differences in electrolyte leakage, peroxidase activity and chlorophyll fluorescence yield following chilling exposure were found. No difference was found on for fatty acid percentage composition of the total glycolipid and phospholipids fraction on the genotypes tested. Sixty percent total fatty acid in glycolipid fraction was C18:2 and C18:3. Fatty acid composition was not a factor in chilling tolerant because it did not vary among the genotypes studied. Differences in leaf anatomy composition were also found among the genotypes tested. However, since there were no differences in diffusive resistance and transpiration rate among the genotypes, stomata density did not affect chilling tolerance through water loss. However, leaf shrinkage differences were found, which indicated differences in water loss. Leaf shrinkage, stomata density, diffusive resistance and transpiration rate may interact with leaf water content and specific leaf weight with respect to leaf water loss under chilling conditions. The results indicated a lower volume of water per unit leaf area.  Therefore these genotypes should exhibit more injury (leaf shrinkage) with an equal amount of water loss. It was concluded that leaf structure and physiological functions could have a role in chilling tolerance and were different among the genotypes tested.