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No description available.

No-tillage establishment into a killed surface mulch on agricultural soil increased marketable acorn squash (Curcurbita pepo L. 'Table Ace’) yield by 29% as compared to a conventional tillage practice. These yield differences are attributed to increased plant population and possible improved water infiltration in no-tillage systems. A no-tillage system in which the surface mulch was suppressed by mowing decreased marketable yields due to possible competition with weeds and the suppressed living mulch cover for nutrients and water. The minesoil yields were reduced due to unavailability of nitrogen (N); however, no-tillage with a killed surface mulch was a more effective treatment when compared to the others. Levels of total N in tissue indicated that a N deficiency did occur in plants grown in all tillage systems in minesoil. Seven nitrogen treatments were investigated: no nitrogen, ammonium, nitrate, urea ammonium nitrate solution (UAN), and UAN in combination with a nitrification inhibitor, nitrapyrin. Two rates of each N source were used, the recommended rate, 80 kg N/ha, and 160 kg N/ha. Squash yields were not affected by the source of N used or by addition of nitrapyrin, but the use of N did increase yields compared to control plots of 0 kg N/ha at both sites. The double rate of N was effective in increasing yields on minesoil, but not on agricultural soil. / Master of Science

Phenotypic effects and transmission rates of the extra chromosome in interspecific trisomics of Cucurbita moschata cv. Butternut (2n C. moschata + 1 C. palmata chromosome) were compared with those of a primary trisomic of C. moschata. Based on gross morphological similarities, 17 interspecific trisomic lines were placed in six phenotypic groups, suggesting that six different C. palmata chromosomes were recovered. Fruit from one of the interspecific trisomics exhibited the hard rind of C. palmata, indicating that this is a dominant trait carried on one chromosome. Some phenotypic effects of the extra chromosome were similar in both the interspecific and primary trisomics, showing a chromosomal effect due to genic imbalance. Transmission of the extra chromosome through the female ranged from 15% to 32% for the C. palmata chromosomes, and was 44% in the primary trisomic. None of the extra chromosomes were transmitted through the male parent.

'Golden Delicious' winter squash (GDWS), Cucurbita maxima Duchesne, provides significant amounts of pollen (24 mg) and nectar (236 μl), but with a low reward of 14% nectar sugar. The quantity of nectar produced per GDWS flower differed between sites and floral sex. The GDWS male flowers had 25% higher sugar concentration than female flowers. There was no statistical difference in the percent of nectar sugars per flower between sites, but the interaction between site and floral sex was statistically significant for the amount of nectar and percent of nectar sugars. Pollen production per flower differed significantly between sites with the most productive site producing 27% more, and 45% more than the other sites. Pollination efficiency of honeybees and bumble bees was assessed with field cages (1.8x1.8x1.8 m). No significant differences were found except for the interaction between the bee treatment and year on number of fruit per cage. This significant difference reflects the increase in fruit number produced by honey bees in 1997. The effect of distance from honey bee hives on fruit and seed quality was tested, and found significant only for B- and C-seeds weight, which were both less in the plots farthest from the nearest group of honey bee hives. Placement of honey bee hives in fields of ≤120 ha appears not to be critical for adequate pollination of GDWS. Other pollinators (excluding honey bees) were frequent visitors to the squash flowers studied here - for example, Bombus spp., Megachilids, Halictids, etc. These other pollinators, mostly bumble bees, accounted for 3.55% of all bee visits. Honey bees visited proportionately more female flowers in the morning, and progressively switched to the more abundant male flowers in the afternoon. This bias differed by site and year. Bumble bees visited proportionally slightly more male GDWS flowers than did female flowers and did it in a similar rate throughout the day. From 15 minute observations each hour of individual female GDWS flower, we calculated that they received approximately 80 honey bee visits per day. / Graduation date: 2001