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- Author or Editor: Vincent A. Fritz x
The objective of this study was to examine seed maturity at harvest as it relates to seed vigor in two commercial shrunken-2 (sh2 J sweet corn hybrids (Zea mays L. var rugosa Bonaf., cvs. Florida Staysweet, Crisp N' `Sweet 710). Seed harvest began at 0.76 g H2O/g fresh weight in 1987 and at 0.70 g H2O/g fresh weight in 1988 and 1989, and was continued at gradually declining moisture levels until frost. In five different tests of seed performance, seed of `Florida Staysweet' (FLASS) harvested between 0.23 to 0.57 g H2O/g fresh weight in 1987 possessed the highest seedling vigor. In 1988 and 1989, maximum vigor was achieved by FLASS seed harvested from 0.40 to 0.60 g H2O/g fresh weight and `Crisp N' Sweet 710' (CNS) seed harvested from 0.45 to 0.65 g H2O/g fresh weight. Standard germination test, seedling growth cold test (SGCT), and seed leachate conductivity provided the most consistent results to `determine optimum seed maturity. Seed weight was not as reliable an indicator of seed vigor in 1988 and 1989 as it was in 1987, and endosperm and embryo weights did not correlate with seedling vigor in any year.
Sand nutrient cultures (containing different Ca2+ compositions) were used to modify the petiole Ca2+ concentrations in Chinese cabbage (Brassica campestris Group pekinensis). Petiole sections (6.5 cm2) from inner and outer leaves, 30 and 60 days after transplanting, were inoculated with Erwinia carotovora ssp. carotovora to evaluate resistance to soft rot incidence and disease progression. Xylem exudates collected from the plants in the sand nutrient culture were analyzed for Ca2+ concentration. Elevated petiole Ca2+ concentrations were not correlated with the development of soft rot in inoculated petiole sections. Plant age and petiole position (inner and outer) did not consistently affect soft rot development. There was a trend of reduced soft rot in inoculated petiole (inner) sections of ‘Hakuran’ plants as the xylem exudate Ca2+ levels increased.
An experimental research seed dryer based on the heat pump principle was built to dry sweet corn (Zea mays var. rugosa L.) seed on husked ears. The dryer is not susceptible to environmentally induced drying rate fluctuations that are common with a conventional open-system forced-air oven. The dryer operates as a closed system and, as a result, provides a more constant drying environment. The ability to control air flow, temperature, and humidity makes the dryer a valuable tool for seed production research.
Changes in the levels of gluconasturtiin (2-phenylethyl glucosinolate), an aromatic glucosinolate, was used to evaluate the response of ‘Green Rocket’ Chinese cabbage (Brassica campestris ssp. pekinensis L.) to the feeding of three and five cabbage looper (Trichoplusia ni Hübner) larvae per plant. Plants were harvested 0, 10, and 17 days after infestation. The change in gluconasturtiin concentration resulting from decreased light capture from diminished leaf area was also studied. All samples were assayed for gluconasturtiin concentration using high-performance liquid chromatography. The gluconasturtiin concentration of plants subjected to five larvae per plant showed a 59% increase 10 days after infestation compared with noninfested plants. Difference in gluconasturtiin concentration between three and five larvae per plant was nonsignificant. Seventeen days after initial infestation and 7 days after larvae were removed (final harvest), gluconasturtiin concentration did not decrease compared with the previous harvest. Reduced light or leaf area removal did not significantly affect gluconasturtiin concentration.
Experiments were conducted to determine if the fungicide imazalil infused into shrunken-2 sweet corn (Zea mays L. var. rugosa Bonaf.) seed via acetone could protect against soil- and seedborne fungi enough to improve germination and vigor. `Florida Staysweet' and `Crisp-n-Sweet 710' seeds were infused for 0.25 hours with 1% or 2% (w/w) imazalil-acetone (LA) solutions, air-dried, and subjected to a modified laboratory seedling growth cold test using sterile soil or soil inoculated with Fusarium moniliforme Sheldon. Both IA concentrations significantly reduced the incidence of diseased seedlings in soil inoculated with F. moniliforme when compared to nontreated controls. Neither treatment significantly reduced the incidence of seedborne fungi. Chemical name used: 1-[2-(2,4-dichlorophenyl)-2-(2-propenyloxy)ethyl-H-imidazole (imazalil).
Glucosinolates (GSL) are bioactive compounds found in cruciferous vegetables that have been shown to have chemopreventive benefits for human health. The objective of this study was to determine whether foliar application of jasmonic acid (JA) increases glucosinolate accumulation and yield in cabbage (Brassica oleracea L. Capitata group). Field studies were conducted in 2004 and 2005 with a green (‘Quisto’) and red (‘Ruby Perfection’) cabbage cultivar. Foliar JA application rates were 0.1 mm, 0.2 mm, and split application of 0.2 mm JA with surfactant, surfactant control, and water control. Yield of both cabbage cultivars was not changed by JA application in both years of the study. In both years, ‘Ruby Perfection’ had significantly higher glucosinolate concentrations than ‘Quisto’ with sinigrin being the predominant glucosinolate in both varieties. JA application consistently increased sinigrin, gluconapin, and glucoiberin concentrations across cultivars and years of the study. JA application also increased progoitrin and total GSL concentrations, but the effect was inconsistent between years and cultivars. In most cases, a split application of 0.2mm JA resulted in the highest GSL accumulation. GSL accumulation was significantly higher in 2005 than 2004 for both cultivars. Climatic data suggest that annual differences in temperature may have influenced the variability in glucosinolate concentration in cabbage.
Glucosinolates (GSLs) are thioglucosides with important properties for plant defense and human health. The objective of this study was to quantify yield and GSL concentration in turnip (Brassica rapa subsp. rapa) roots and shoots as influenced by colored plastic mulches. Four turnip cultivars (‘Just Right’, ‘Purple Top’, ‘Royal Crown’, and ‘Scarlet Queen’) were grown over five mulch treatments: white, yellow, silver, red, blue, and a bare soil control in both a May and an August planting in 2006 and 2007. Yield varied by variety; however, there was no consistent relationship between mulch treatment and yield. Glucosinolate concentrations and profiles varied with tissue type, genotype, and environmental factors, including temperature and planting date. Mulch-dependent increases in GSL concentrations were not consistent across tissue types, cultivars, planting dates, and years of the study, possibly as a result of differences in climatic factors and mulch-dependent changes in soil temperature between planting dates and years of the study.
Ethephon and 2,4-D were foliarly applied to red-skinned `Norland' potatoes (Solarium tuberosum L.) to determine if periderm color could be enhanced at harvest and throughout storage. Base rates of 250 and 185 ml·liter–1 for ethephon and 2,4-D, respectively, were applied at the onset of tuberization (tubers ≥ 2.5 cm in diameter). Base or double-rate foliar applications of either ethephon or 2,4-D resulted in significant U.S. No. 1 yield reductions and did not affect periderm color intensity at harvest or throughout storage sufficiently to warrant their use. Chemical names used: (2-chloroethyl)phosphonic acid (ethephon), (2,4 -dichlorophenoxy) acetic acid (2,4-D).