The chelating agents, monocalcium disodium salt of ethylenediaminetetraacetic acid (CaNa2EDTA) and sodium hexametaphosphate (Na-HMP), at 800 ppm, were used for canning ‘Honey Sweet’ carrots, ‘Van’ sweet cherries, and ‘Large Early Montgament’ apricots with water containing 0, 20, 40, 80, and 160 ppm of Ca and 20 ppm of magnesium. The control cans did not contain EDTA or Na-HMP.
The canned carrots, cherries, and apricots were stored at 70° or 100°F. Evaluations were made at 60-day intervals for 6 months. All 3 commodities had better organoleptic acceptibility when they were canned with CaNa2 EDTA or Na-HMP than the controls.
Carrots canned with CaNa2EDTA were firmer and retained better color than those canned with Na-HMP or the controls. The rate of loss of firmness and color increased with time of storage. Retention of firmness, volatile reducing substances, pH, and taste quality was improved in sweet cherries and apricots canned with CaNa2EDTA or Na-HMP.
Petunia ×hybrida (Hook) Vilm. cv. Mitchell was transformed with an E. coli gene encoding mannitol-1-phosphate dehydrogenase (mtlD). Four plant lines that grew on kanamycin and contained the mtlD transgene were identified. Two of these lines contained high levels of mannitol [high-mannitol lines M3 and M8; mean mannitol = 3.39 μmol·g-1 dry weight (DW)] compared to nontransformed wild-type plants (0.86 μmol·g-1 DW), while two lines had mannitol levels similar to wild-type plants (low-mannitol lines M2 and M9; mean mannitol = 1.05 μmol·g-1 DW). Transgenic and control plants were subjected to chilling stress (3 ± 0.5 °C day/0 ± 0.5 °C night, 12-hour photoperiod and 75% relative humidity) to evaluate the role of mannitol in chilling tolerance. Based upon foliage symptoms and membrane leakage after a 3-week chilling treatment, the high-mannitol containing lines, M3 and M8, were more tolerant of chilling stress than the low-mannitol containing transgenic lines, M2 and M9, and wild-type. Under nonchilling conditions mannitol was the only carbohydrate that differed among transgenic lines, but all carbohydrates were present. When subjected to chilling stress, mannitol levels dropped by 75%, sucrose by 52%, and inositol by 54% in the low-mannitol lines (M2 and M9). In M3 and M8, the high-mannitol lines, mannitol levels decreased by 36%, sucrose by 25%, and inositol by 56%, respectively. Raffinose increased 2- to 3-fold in all lines following exposure to low-temperature chilling stress. In the higher mannitol lines only 0.04% to 0.06% of the total osmotic potential generated from all solutes could be attributed to mannitol, thus its action is more like that of an osmoprotectant rather than an osmoregulator. This study demonstrates that metabolic engineering of osmoprotectant synthesis pathways can be used to improve stress tolerance in horticultural crops.