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The population of U.S. Asians will increase by 41% and reach 12 million by the year 2000. Chinese cabbage, Pak Choi, Daikon, and Bitter melon have moved out of the ethnic market and are now in mainstream outlets. This study targeted a diverse range of cool and warm-season crops. Besides those listed above, this study evaluated varieties of Asian greens, Chinese brocolli, Allium, edible soybeam, melon, squash, cucumber, edible Chrysanthemum, amaranth, winged bean, yard-long bean, and edible soybean. A randomized complete block design was utilized, with three replications of row length, varying from 10 to 33 feet, depending on species tested. Direct seedlings of cool-season crops in February and September, 1989 resulted in good market quality and yield of many varieties. Work in 1990 will focus on width of the market window, market information, and grower access to markets.
Setup and administration of comprehensive live plant identification (ID) tests in horticulture classes is time-consuming and costly. The curricular goal of this study was to integrate Web-based plant ID self-tests and computer-graded tests into floriculture potted plant production classes to potentially replace live plant ID tests. This research was conducted during 2000 and 2001 with students enrolled in Hort 4051 at the University of Minnesota, St. Paul. All plant ID tests were mandatory, constituting 12% of the grade. In 2000, only Web-based ID tests were used, while both Web-based and live plant ID tests were used in 2001. Two separate self-tests were designed as study aids with 34 randomized photographs/test. Correct spelling was mandatory to receive full credit for genus, species, and family. Self-tests could be taken ten times each per student. Students then completed two for-credit (graded), unmonitored Web-based tests. Students completed a Website evaluation form at the end of the semester. The two live plant ID tests were conducted with the same materials and were monitored. Mean student scores for the Web-based ID tests in 2000 ranged from 73.5 to 99.5% with a class average of 91.9%; there were no significant differencesamong students' scores. Student Web-based ID test scores for 2001 had a similar range with a high class average of 93.8%. In contrast, the 2001 live plant ID tests had a wider score range of 21.7% to 100.0% and lower class average (72.2%). Web-based and live plant ID tests, students, and their interaction were all highly significant. Web site course evaluations demonstrated interesting trends in student perception of Web-based and live plant testing. The implications for future class use and potential modifications for continued Web-based instruction are presented.
In the production of fresh-market vegetables, off-farm inputs, such as, plastic, nitrogen fertilizer, fungicides, insecticides, and herbicides are routinely used. One aim of the sustainable agriculture program at the Beltsville Agricultural Research Center is to develop systems that reduce these inputs. We have completed the second year of a study designed to examine foliar disease progress, foliar disease management, and marketable fruit yield in staked fresh-market tomatoes grown in low- and high-input production systems. Specifically, four culture practices (black plastic mulch, hairy vetch mulch, dairy manure compost, and bare ground) were compared in conjunction with three foliar disease management treatments (no fungicide, weekly fungicide, and a foliar disease forecasting model, TOMCAST). Within all culture practices, use of the TOMCAST model reduced fungicide input nearly 50%, compared with the weekly fungicide treatment, without compromising productivity or disease management. With regard to disease level, a significant reduction of early blight disease severity within the hairy vetch mulch was observed in 1997 in relation to the other culture practices. Early blight disease severity within the black plastic and hairy vetch mulches was significantly less than that observed in the bare ground and compost treatments in 1998. In addition, despite a 50 % reduction in synthetic nitrogen input, the hairy vetch mulch generated yields of marketable fruit comparable to or greater than the other culture practices. It appears that low-input, sustainable, production systems can be developed that reduce the dependence on off-farm inputs of plastic, nitrogen fertilizer, and pesticides, yet generate competitive yields.
Abstract
Strategies for reducing bacterially induced frost damage to tender plants were examined. Introduction of the competitive bacterium, Erwinia herbicola M232A (not active in ice nucleation) did not lower the temperature at which freeze injury of tomato shoots occurred. Streptomycin was effective in reducing freeze damage of tomato shoots only when mixed with the Pseudomonas syringae suspension prior to plant inoculation. Spectinomycin, another aminoglycoside, was effective in reducing frost damage to tomato plants due to P. syringae. Bacteria present intercellularly (within the plant) may play a significant role in bacterial ice nucleation.
Petioles were gathered at bloomtime in four trials, one each of `Chardonnay and `Zinfadel' and two of `Cabernet Sauvignon' over 2 years, 1993 and 1994. In each trial, scions were grafted onto 12 to 14 rootstocks. Petioles were analyzed for NO3-nitrogen, NH4-N, K, P, and Mg. NO3-N levels differed among rootstocks by as much as 16-fold (126 to 2064 μg·g–1), NH4-N by as much as 4-fold (253 to 1-28 μg·g–1), K, P, and Mg by about 3-fold (9.7 to 30.6 mg·g–1, 1.8 to 6.3 mg·g–1, and 2.9 to 7.5 mg·g–1, respectively). `Freedom' had the highest levels of NO3-N. `Salt Creek' had moderate levels of NO3-N, but had the highest levels of NH4-N. The rootstock 420A Mgt was consistently low in NO3-N, NH4-N, and K. Freedom was among the highest in K content. The rootstock 44-53 Malègue' had high levels of K and low Mg. Implications for vineyard fertilization programs will be discussed.
The change from asexual to sexual propagation for annual and perennial bedding plants has been successfully accomplished for floral crops, e.g., Pelargonium. Seed-propagated cultivars do not necessarily possess the clonal uniformity of vegetatively propagated cultivars. In the development of F1 hybrid garden chrysanthemums, this lack of uniformity was assessed with the use of consumer sensory evaluations. Seedlings (n = 10–20 plants/cross) were transplanted for field trials in St. Paul and five Minnesota branch stations each year during 1988–94 to test for G × E. Early flowering F1 hybrids, developed from inbred parents with general combining ability, were evaluated for flowering earliness, plant uniformity, and a general rating. Consumer rankings of top performers were not significantly different (5% level) from mum breeders. The top performers for all three ratings were selected each year for repeat evaluation the next year. The two highest performing F1 hybrids were submitted for All American Selection Trials in 1995.
A `Montmorency' sour cherry planting was established on 20 clonal rootstocks in April, 1987, as part of the NC-140 cherry rootstock trial. After 5 seasons scion/rootstock combinations showed a 2.5-fold range in trunk circumference. During the fifth season there was a 6-day range in bloom date, a 4-fold range in growth rate, a 7.5-fold range in yield and a 3-fold range in yield efficiency as influenced by rootstock. Trees on GM 9 were the smallest, had the lowest yields, smallest fruit and were among the lowest in yield efficiency. Mahaleb has been the standard cherry rootstock in Utah. Rootstocks whose trees were comparable or exceeded those on mahaleb in both yield and yield efficiency during the fifth season included 148-1, 196-13 and M×M 2. Differences were also observed in root sucker tendency.
Calcium chloride (CaCl2) enhances turgidity and quality of postharvest sour cherry, Prunus cerasus L., fruit. Mechanisms by which plasma membrane (PM) ATPase maintains the electrochemical gradient in cell turgor were studied in isolated PM vesicles isolated from tapwater-, CaCl2- and chelated amino acid-calcium-treated Montmorency sour cherry fruit. Electron microscopy and periodic-chromicphosphotungstic acid staining indicated 85-90% closed PM vesicles. Protein activity associated with the PM was four times higher in both Ca treatments than in untreated cherries. ATPase activity was insensitive to NO3 and NaN3, but inhibited by vanadate, indicating absence or low levels of tonoplast and mitochondrial ATPases. PM vesicles exhibited a pH jump in the presence of acridine orange (A493-530nm). Cherry fruit appeared to have a PM ATPase similar to that of other plant species. Generation of a positive membrane potential across the PM was dependent upon ATP.
Abstract
Leaves of cold-acclimated lemon [Citrus limon (L.) Burm. f.], grapefruit (C. paradisi Macf.), orange [C. sinensis (L.) Osbeck], and mandarin (C. unshiu Marc.) trees ranged in cold hardiness from −4 to −11°C. No significant differences in water content (g H2O/g dry weight) or melting point depression were observed. Plots of liquid water content during freezing (g H2O/g dry weight) vs. temperature were similar for the 4 citrus species. The tissues apparently deviated from ideal freezing behavior because less ice was formed. The reduced ice formation could not be accounted for by osmotic effects. Negative pressure potential developed during freezing is hypothesized to play a role in tissue water potential in frozen systems. It was concluded that hardier Citrus leaves survive freezing of a larger fraction of their tissue water.
Isoenzyme staining of horizontal starch gels was used to characterize 23 cultivars and three advanced selections of red raspberry (Rubus idaeus L.). The genotypes were separable using the enzymes malate dehydrogenase, phosphoglucoisomerase, phosphoglucomutase, and triose phosphate isomerase. In addition, staining for isocitrate dehydrogenase and shikimate dehydrogenase revealed polymorphisms in some cultivars. By combining these results with those obtained for 78 previously tested cultivars, 75 of the 104 (72%) genotypes tested were uniquely characterized using the six isoenzymes.