Search Results
Abstract
Inheritance and selection of heat tolerance were investigated in common bean (Phaseolus vulgaris L.). Parental, F1, backcross, and F2 populations from the crosses PI 271998 × BBL 47, PI 271998 × 80 BP-6 and 5BP-7 × BBL 47 were used in the inheritance study. Parental, F2, F3 and backcross populations of the cross PI 271998 × BBL 47 were used to estimate selection gain. Plants were evaluated for heat tolerance by the conductivity method after 32 days in the growth chamber at 20°/15°C (day/night) and acclimation at 37° for 24 hr. The joint scaling test indicated that the additive-dominance model was adequate to explain heat tolerance in crosses PI 271998 × BBL 47 and 5BP-7 × BBL 47. The major variation for tolerance for these 2 crosses may be controlled by a small number of genes. The additive-dominance model was inadequate for PI 271998 × 80BP-6, however, and epistasis was present. Narrow sense heritability estimates ranged from 2.9% to 24.0%, indicating relatively small additive effects. Broad sense heritability estimates ranged from 0.0% to 21.6%, suggesting sizable environmental effects. Realized heritability from selection for tolerant F2 plants was 7.9%. These estimates perhaps represent the lower limit of heritability for heat tolerance. The conductivity method could be considered for evaluating heat tolerance in a breeding program but should be more effective in screening F3 families than individual F2 plants.
Forty selections, including 37 cultivars of Hamamelis spp., were evaluated for genetic similarities using randomly amplified polymorphic DNA (RAPD) markers. Cluster analysis identified seven groups, which included three groups of H. ×intermedia cultivars, two groups of H. vernalis, and one group each of H. mollis and H. japonica. Three H. ×intermedia cultivars, `Arnold Promise', `Westerstede', and `Carmine Red', did not group closely with the other 20 cultivars of H. ×intermedia. Selections of the North American species H. vernalis were quite distinct from the Asiatic selections. However, data are presented that suggest hybridization exist between Asiatic Hamamelis spp. and H. vernalis. Genetic similarities between known half-sib families provides evidence that the cultivar pairs `Arnold Promise'—`Winter Beauty' and `Carmine Red'—`Hiltingbury' are, themselves, not likely half-sibs.
Leaf tissue from 10 Buxus spp. cultivars were collected and evaluated for differences in isozyme and random amplified polymorphic DNA (RAPD) markers. In addition, samples of named cultivars were collected from multiple locations to estimate the degree of cultivar fidelity across locations. In general, isozymes were highly polymorphic among cultivars. Aconitase, malate dehydrogenase, aminoaspartate transferase, and phosphoglucose isomerase were the most useful isozymes to distinguish among the selected clones. Good quality DNA was readily extracted from leaf tissue using a standard CTAB procedure. RAPDs were generated from polymerase chain reactions using a random set of primers. Of 200 primers that were screened, 20 gave reproducible and polymorphic patterns that could be used to distinguish among the boxwood cultivars. In general, cultivar fidelity among commercial nurseries was fair. Biochemical analyses could be used to resolve problems with cultivar identity once baseline information is collected.
Fairy ring has become a troublesome and persistent disease on golf course putting greens and other turf areas in most regions of the United States. Many basidiomycete fungi are associated with this destructive disease in turfgrass. Recent widespread epidemics of fairy ring have led investigators to examine possible management and control options. Curative approaches include topical flutolanil fungicide applications in conjunction with soil surfactants, the application of flutolanil under high-pressure injection, and the use of nitrogen fertility programs. These curative programs were effective at suppressing visual symptoms and turfgrass injury. A preventive approach evaluated repeat applications of flutolanil plus a soil surfactant prior to disease development. This preventive program was effective at eliminating visual disease symptoms on bermudagrass putting greens. Information presented will review results from field research studies conducted over the past 3 years in Florida, North Carolina, Ohio, Texas, and Virginia.
Red-fleshed watermelons contain lycopene, a compound that has health functional properties. Watermelon intake may be restricted for individuals who have diabetes or those who limit carbohydrate intake. Recently, a low-sugar watermelon (<6% soluble solids content) was developed using traditional plant breeding techniques. Low-sugar and a commercial variety of watermelon (9% SSC) were washed, cut in half and red flesh was removed and cut into cubes. Low and high levels of artificial sweetener were added to the low-sugar watermelon. Students at a Native American school (grades 1 through 12) and adults at a Native American Feeding Center were asked to rate how much they liked or disliked the watermelon using a seven-point hedonic scale. Lycopene and other carotenoids were analyzed from samples using established methods. Artificially sweetened melons were rated as acceptable as commercial control melons for taste. Lycopene and total carotenoid levels were similar among the treatments. These results show that artificially sweetened low-sugar watermelons were acceptable to Native American consumer groups.
Bacterial speck caused by Pseudomonas syringae pv tomato is a major springtime disease of tomato during rainy weather conditions in California. Application timing as a calendar spray was compared to pre-anticipated rainfall treatments of either cupric hydroxide alone or in a combined tank-mix with mancozeb. Plots were established in grower fields with natural infestations. In some instances, moderately severe infestations of speck caused as much as a 25% reduction in yield and slight delays in fruit maturity. Timing of treatments prior to rainfall was superior to calendar sprays. Slight improvement in disease suppression was achieved with a tank mix of mancozeb with copper compared to copper alone.
Abstract
Shoot tip cuttings of cucumber (Cucumis sativus L.) taken at various times, ages, and condition were subjected to several pre- and post-selection techniques known to influence rooting in other species. Succinic acid-2,2-dimethylhydrazide (SADH) applied 1 week before shoot tip harvest increased the rooting of cuttings. Neither time of day cuttings were prepared (7 AM or 1 PM) nor fruit load influenced rooting. Sand culture under mist, at 27°C (day), 21° (night), in the greenhouse was superior to other rooting methods tested. Cultivars varied in rooting. Cuttings from early planting rooted better than those from late plantings.
Abstract
7-Oxabicyclo (2.2.1) heptane, 2-3-dicarboxylic acid (endothall) alone was not an effective chemical abscissor of bean leaves (Phaseolus vulgaris L. cv. Red Kidney) until a concn of 30 to 40 mg/liter was attained, but in the presence of 800 mg/liter (2-chloroethyl)phosphonic acid (ethephon) abscission began at 5 mg/liter endothall. Low pH (1.5) significantly lowered the break strength of abscission zone explants of leaves sprayed with ethephon and endothall compared to pH 6.0, and endogenous ethylene production from endothall alone was higher at pH 1.5 than pH 6.0.
A computerized information delivery system (AgTiIPS) was developed to deliver lawn, garden, and horticultural information to the public. AgTiIPS was based on voice-mail technology, which allows the public to access about 100 messages through a tone-producing telephone. AgTiIPS has been functioning in a Wyoming community of 47,000 since July 1990, and has delivered more than 700 messages in 1.5 years. Economic analyses for setting up voice-mail systems were conducted and the role of voice-mail in delivering lawn, garden, and horticultural information was discussed.