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`Beauregard' sweetpotato (Ipomoea batatas L. Lam) roots were maintained under different controlled atmospheres ranging from 0% to 21% O2 at 22 °C in two separate trials for 14 days to study changes in activities of pyruvate decarboxylase (PDC) and alcohol dehydrogenase (ADH). Trial I showed no difference in activities of PDC and ADH between 0% and 1% O2, or among 2%, 5%, and 21% O2. Both PDC and ADH activities were significantly higher at 0% and 1% O2 compared to the 2%, 5%, and 21% O2 atmospheres. In trial II, both enzyme activities were lower at 1.5% O2 than at 0% O2, but higher than at 10% and 21% O2 atmospheres. The combined data of the two trials showed a very strong correlation between PDC and ADH activities (R 2 = 0.86). In addition, a strong correlation existed between PDC activity and acetaldehyde concentration (R 2 = 0.95). The maximal activities were at pH 6.5 for PDC and at pH 8.5 for ADH in the direction of acetaldehyde-to-ethanol. The results suggest that 1.5% O2 is the critical point for the transition from aerobic to anaerobic metabolism in CA storage of sweetpotato roots, and PDC is the key enzyme in alcoholic fermentation.
In a screening test of 76 PIs, commercial Chinese watermelons, and `Crimson Sweet', PI512385 had the highest disease resistance with a mean rating of 4.5 on a 1-9 scale with 1 = resistant and 9 = susceptible. A second test with PI512385 included material with previously reported resistance (PIs 270550, 326515, 271775, 271779, 203551, 299379 and 189225) and `Crimson Sweet', a susceptible check showed PI512385 had significantly more resistance than `Crimson Sweet' but was not significantly more resistant than the PIs. PI512385 had a mean rating of 2.2 in the second test.
Transgenic spinach (Spinacia oleracea L., cv. High Pack) plants were regenerated from callus derived from hypocotyl segments. Explants were cocultivated for 48 h with Agrobacterium tumefaciens harboring pMON 9749 plasmid conferring kanamycin resistance and β-glucuronidase (GUS) activity. To induce callus, the explants were cultured on Murashige and Skoog (MS) selective medium containing 2 mg L-1 kinetin and 0.5 mg L-1 2,4-D. Shoots developed from the callus upon transfer to selective regeneration medium supplemented with 2 mg L-1 kinetin, 0.01 mg L-1 2,4-D, and 1 mg L-1 GA3. Shoots were rooted on MS medium containing 1 mg L-1 IBA. Excluding the cocultivation medium, all others were supplemented with 50 mg L-1 kanamycin, 100 mg L-1 cefotaxime, and 100 mg L-1 carbenicillin. To confirm transformation, kanamycin-resistant callus and leaf sections from regenerants were assayed for GUS activity using the X-gluc assay. Stable GUS gene expression in transgenic plants was demonstrated. This is the first report of regenerating transformed spinach.