Harvested roots of 2 cultivars of sweet potato [Ipomoea batatas (L.) Lam.] were submerged in water to simulate flooding damage and changes in the concentrations of carbon dioxide, oxygen, and nitrogen were followed in the internal gas atmospheres. The internal gas was almost exclusively CO2, 72 hours after submergence.
Plants of sweet potato (Ipomoea batatas (L.) Lam) were exposed prior to harvest to 1 week of warm-dry, warm-flooded, cold-dry or cold-flooded soil conditions. Roots harvested from the warm-flooded soil showed more rotting during curing than roots from the other treatments, and rotting continued during storage. Roots harvested from the cold-flooded soil rotted to a lesser extent during curing but rotted rapidly during storage. Roots harvested from the cold-dry soil showed no rotting during curing; however after 52 days of storage, the number of roots with rot increased sharply. Root respiration rates from cold-flooded, cold-dry, and warm-flooded soils were not significantly different, but those rates were much higher than the rate in roots from warm-dry soil. ‘Jewel’ had a lower respiration rate than NC 317. The cold treatments stimulated sprouting of sweet potato roots during storage. ‘Caromex’ showed the highest sprouting followed by ‘Jewel’, NC 317, and ‘Centennial’.
Biolistic transformation methods for zoysiagrasses (Korean lawngrass) were developed and used to introduce a herbicide-resistant trait. Embryogenic calli were induced from mature caryopses on MS medium supplemented with 2 mg/L of 2,4-D, and used to establish liquid agitation cultures. The cultures have been maintained over a year without loss of the embryogenic competence. A particle bombardment method was optimized for zoysiagrass based on transient gusA gene expression. The most transient GUS expression upon bombardment treatments occurred at 1100 psi of helium pressure with 10 cm of particle flying distance and 0.125 M sorbitol preculture treatment. Promoters suitable for zoysiagrass were compared, and actin and ubiquitin promoters were found effective in expressing gusA gene. Vector DNAs containing a herbicide resistant gene (bar), pBY505, were introduced into embryogenic cells of zoysiagrass using the optimized method. Total 194 putatively transformed plants were regenerated from 60 biolistic plates for over 6 months through selection culture containing 4-10 mg/L of phosphinothricin. Regenerants were grown in potting soil in greenhouse and sprayed with 1.7 g/L of Ignite herbicide. The transgenic plants showed various levels of resistance to the herbicide, while untransformed control plants were all dead. Recombination of the bar gene into the genomes of the transformants were confirmed through PCR and Southern blot analysis.