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Vladimir Meglic, Jack E. Staub, and Larry D. Knerr

Thirty-eight cultivated accessions of the diverse Cucurbitaceae were electrophoretically surveyed using 13 enzyme systems. Included were representatives from 6 of the 6 Cucurbitaceae tribes, 9 genera, and 17 species. Additionally, several cultivars or groups were included for those species possessing marked morphological diversity such as the 7 groups of Cucumis melo var. melo and 7 of the numerous cultivars representing Cucurbita pepo. Zymograms were scored for the presence or absence of bands measured in mm from the origin. Cluster analysis (complete linkage method) was used to detect affinities among the accession surveyed. Data suggest that: 1) Cucumis melo (x=12) possessed greater biochemical affinity with C. sativus (x=7) than with either C. anguira or C. metuliferus (both x=12); 2) Sechium edule and Cyclanthera pedata. both members of the tribe Sicyeae, were more closely associated with members of other tribes than with each other; 3) Some cultivars of Cucurbita pepo shared greater affinity with Cucurbita moschata than with other cultivars of C. pepo. Additional observations as well as their possible implications will be presented.

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William J. Lamont Jr.

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William J. Lamont Jr.

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B.D. Bruton, T.W. Popham, J. García-Jiménez, J. Armengol, and M.E. Miller

Thirty-seven species within Cucurbitaceae representing the genera Citrullus, Cucumis, Cucurbita, Lagenaria, and Luffa were evaluated for disease reaction to an Acremonium cucurbitacearum A. Alfaro-Garcia, W. Gams, and Garcia-Jimenez, isolate (TX 941022) from the Lower Rio Grande Valley of Texas. After 28 days in the greenhouse, seedling disease ratings were made on the hypocotyl, stem-root junction, primary root, and secondary roots. An additional disease measure was derived by averaging the four root disease ratings to establish a disease severity index (DSI). Vine and root dry weight were poor measures of plant damage caused by A. cucurbitacearum. According to the DSI, all species within Cucurbita, Lagenaria, Luffa, and three Cucumis sativus L. cultigens were rated as highly resistant to A. cucurbitacearum. Cucumis melo L. and Citrullus lanatus (Thunb.) Matsum. & Nakai cultigens were the only cucurbits receiving DSI ratings of moderately resistant to susceptible.

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Abigail Attavar, Lydia Tymon, Penelope Perkins-Veazie, and Carol A. Miles

depicting ( A ) areas where presence of V. dahliae is documented, adapted from Pegg (1984) and ( B ) countries from which Cucurbitaceae germplasm used in this study were collected by the U.S. Department of Agriculture National Plant Germplasm System

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Ilse-Yazmín Arciniega-Carreón, Carmen Oliver-Salvador, María-Guadalupe Ramírez-Sotelo, and Carlos Edmundo Salas

as “wereke” or “guareque,” traditionally used to treat diabetes, ulcers, and metabolic disorders ( Johnson et al., 1996 ; Xolalpa, 2002 ). It belongs to the Cucurbitaceae family, and it is native to arid areas from northern Mexico ( Lira and

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M.S. Stanghellini, J.R. Schultheis, and J.T. Ambrose

Very little is known about the rate at which pollen grains are mobilized within insect-pollinated crop systems, and this is especially true the for commercial production of field-grown cucumber (Cucumis sativus L.), monoecious muskmelon (Cucumis melo L.), and triploid watermelon [Citrullus lanatus (Thunb.) Matsum. & Nakai]. The rates of pollen depletion for these crops were therefore investigated on plots simulating commercial crop production using a mixed honey bee (Apis mellifera L.) and bumble bee (Bombus impatiens Cresson) pollinator complex. At anthesis, staminate cucumber, muskmelon, and watermelon flowers contained on average 10539, 11176, and 30739 pollen grains/flower, respectively. At the time flowers closed in the early afternoon (1300 to 1400 hr), only 61% of the total pollen produced had been removed from staminate cucumber flowers, 44% to 62% from muskmelon, and 81% from watermelon flowers. The results suggest that total pollen production in these crops may not necessarily reflect total pollen availability to floral visitors (bees). However, of the total amount of pollen actually removed per flower, >57% occurred during the 2 h following flower anthesis of cucumber and muskmelon, and >77% occurred during the 2 h following flower anthesis of watermelon. Thus, most of the accessible pollen was removed shortly after anthesis, which is when these crops are most receptive to pollination. Nonviable triploid and viable diploid watermelon pollen were removed at similar rates (P = 0.4604). While correlation analyses were not possible for the influence of variable bee abundance on pollen depletion rates, higher bee populations in one year appeared to increase the rate at which pollen grains were removed from staminate flowers.

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Joshua H. Freeman, Stephen M. Olson, and William M. Stall

Successful fruit set in triploid watermelons [Citrullus lanatus (Thunb.) Matsum. & Nakai] requires a diploid watermelon cultivar, or pollenizer, to be planted nearby as a pollen source. Pollenizer cultivars have been developed to be planted in-row with triploid plants without spacing change, which decreases area per plant. These cultivars have different growth habits, from highly reduced foliage to standard foliage, and it is uncertain how pollenizer growth habit may affect triploid plant growth and yield. Two diploid watermelon pollenizers, ‘Mickylee’ and ‘SP-1’, with markedly different growth habits were planted at five in-row spacings from triploid plants to determine the effect of plant competition on triploid watermelon yield. All treatments used a 1:1 pollenizer to triploid ratio to measure the direct effect of pollenizer growth on associated triploid yields. Experiments were conducted at two locations during Spring 2006 (Quincy and Citra, FL) and one during Fall 2006 (Quincy). Triploid plants paired with ‘Mickylee’ yielded 11.4% (Citra) and 22.4% (Quincy) less weight in the spring and 8.5% less in the fall than plants paired with ‘SP-1’ and also produced fewer fruits per plant. However, the results from the fall trial were not significant. Pollenizer to triploid spacing had a linear effect on yield per plant and fruits per plant, and there was no interaction between pollenizer cultivar and spacing. The use of ‘Mickylee’ as a pollenizer may be an attractive option because of lower seed costs compared with other pollenizers, but these results indicated lower triploid watermelon yields from plants paired with ‘Mickylee’, which is most likely a result of increased plant competition.

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Robert J. Dufault

Abstract

Pretransplanting nutritional conditioning (PNC) regimes were evaluated for their effects on improving tolerance to transplant shock and increasing early fruit production. Muskmelon seedlings (Cucumis melo var. reticulatus L. ‘Magnum 45’) were fertilized twice weekly with solutions containing N, P, and K to determine nutrient needs required to produce high-quality transplants. Seedling height, stem diameter, leaf area, shoot and root dry weights, leaf number, and shoot: root ratios of 27-day-old transplants increased as N rates increased from 10 to 250 mg liter−1. These growth variables also increased with P from 5 to 25 mg·liter−1 but decreased as P increased from 25 to 125 mgliter−1. Increasing K rates from 10 to 250 mg·liter−1 increased seedling height, stem diameter, and leaf area. Nine PNC regimes ranging from low to high N-P-K status were tested under field conditions to determine any long-term advantage. Generally, as PNC levels increased, transplant shock (percentage of necrotic leaves) increased as measured 12 days after transplanting. However, vining, female flowering, fruit set, and early yields increased as PNC levels increased. A high level of PNC (250N-125P-250K, mg·liter−1) conditioned transplants to overcome shock and to resume growth sooner and yield earlier than those at lower PNC levels.

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A. Benzioni, S. Mendlinger, M. Ventura, and S. Huyskens

Seed germination, growth, flowering, and yields of Cucumis metuliferus Mey. were examined in several seasons and conditions in the northern Negev, Israel. Germination was optimal between 20 and 35C. Germination was delayed at 12C, totally inhibited at SC, and greatly inhibited above 35C. Salinity increased the time required for full germination. Plants sown in mid-March set fruit in mid-May and gave a higher yield of export-quality fruits than plants sown in mid-April, which set fruit normally but produced a large proportion of small (<200 g) fruits. Plants sown in June did not flower until October. C. metuliferus sown in a greenhouse on three dates in October and November developed very slowly during the cold months and leaves were chlorotic; however, fast growth and development resumed in the spring and high yields were eventually achieved.