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Rebecca Nelson Brown and James R. Myers

A molecular and morphological marker map would improve our knowledge of Cucurbita genetics, and would facilitate efforts to breed improved summer and winter squash cultivars. Random amplified polymorphic DNA (RAPD) markers were used to construct a partial map of the Cucurbita genome. The mapping population was the BC1 progeny of the Cucurbita pepo L. yellow straightneck inbred A0449 and the tropical Cucurbita moschata Duchesne ex Lam. landrace `Nigerian Local'. A0449 was the recurrent parent. This cross was chosen because of the relatively greater economic importance of summer squash, traits of value to be introgressed from the C. moschata parent, and maximized genetic variation from the interspecific cross. The map contains 148 RAPD markers in 28 linkage groups. Loci controlling five morphological traits were placed on the map. The map covers 1,954 cM, which is estimated to be 75% of the Cucurbita genome. The qualitative traits placed on the map include the B gene for fruit which turn yellow before anthesis, the M gene for silver mottling of leaves, and a locus controlling the intensity of rind color on mature fruit. Quantitative trait loci (QTL) associated with fruit shape and the depth of the indentations between primary leaf veins were identified.

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H.C. Wien, S.C. Stapleton, D.N. Maynard, C. McClurg, and D. Riggs

Field production of decorative pumpkins (Cucurbita pepo L.) in New York occasionally results in markedly delayed fruit production in spite of normal vine growth. These episodes of fruitlessness appear to be associated with periods of high temperatures. To determine the link between temperature and pumpkin flowering and fruiting, a series of multilocational field trials and confirmatory greenhouse experiments were carried out. The field trials were conducted in the summer seasons of 1996 and 1997 in Ithaca and Albany, N.Y.; Queenstown, Md.; and Bradenton, Fla.; and in Ithaca and Bradenton in 1998. Mean growing season temperatures were 20, 21, 24 and 28 °C, respectively, at the four locations in 1996 and 1997. Delay in fruit formation was indicated by the main stem node number at which the first fruit developed. In Ithaca and Albany, the six cultivars formed their first fruit at node 17, but fruit production shifted to node 24 at Queenstown, and to node 26 or more at Bradenton. The prolonged delay in fruiting at the warmest site resulted in a 74% decrease in total yield of the C. pepo cultivars in 1996 and 1997, compared to Ithaca and Queenstown. In contrast, the yields and yield components of the C. maxima cultivar Prizewinner were similar at all four sites. Greenhouse trials in which `Howden' and `Baby Bear' were grown at 32/27, 25/20, and 20/15 °C confirmed that high temperatures delay formation and anthesis of female flowers. This and other published work indicates that there are genetic differences in susceptibility to high temperature flower delay that could be exploited to improve pumpkin performance.

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Kent E. Cushman, Thomas E. Horgan, David H. Nagel, and Patrick D. Gerard

Pumpkins (Cucurbita pepo, C. moshata) were grown in northern Mississippi during 2000 and 2001 for the purpose of more narrowly defining plant population recommendations for commercial production in the humid southeastern United States. Four plant populations were examined for `Aspen': 908, 1361, 2045, and 3068 plants/acre (2244, 3363, 5053, and 7581 plants/ha, respectively) and for `Howden Biggie': 605, 908, 1361, and 2045 plants/acre (1495, 2244, 3363, 5053 plants/ha, respectively). Plant populations were adjusted by varying in-row spacing while holding between-row spacing constant at 8 ft (2.4 m). Plant population significantly affected yield of `Aspen' and `Howden Biggie'. Linear and quadratic terms were significant for `Aspen', with maximum yield (ton/acre and fruit/acre) for the quadratic relationship occurring at about 2045 plants/acre. In contrast, yield of `Howden Biggie' decreased significantly (ton/acre) and nonsignificantly (fruit/acre) in a linear relationship as plant population increased from 605 to 2045 plants/acre. Plant population significantly affected fruit weight and size. As plant population increased, weight and size decreased slightly but significantly in a linear relationship for `Aspen' (lb/fruit and inch3/fruit) and `Howden Biggie' (lb/fruit). The quadratic relationship for `Howden Biggie' (inch3/fruit) was significant and the minimum value occurred at about 1361 plants/acre. Plant population significantly affected pumpkin yield components associated with plant productivity. As plant population increased, number and weight of fruit per plant decreased sharply in a quadratic relationship for `Aspen' (lb/ plant and fruit/plant) and `Howden Biggie' (lb/plant). The linear relationship for `Howden Biggie' (fruit/ plant) also decreased significantly. At the highest plant populations for `Howden Biggie', 40% of the plants did not produce marketable pumpkins. In conclusion, recommendations of optimum plant populations for a semi-vining cultivar such as `Aspen' should be centered on about 2045 plants/acre. Published recommendations from Kentucky appear sound, advocating plant populations within the range of 1360 to 2720 plants/acre (3361 to 6721 plants/ha). For a vining cultivar such as `Howden Biggie', recommendations can be as low as 605 plants/acre. Published recommendations from Kentucky and Georgia, along with those published in the Vegetable Crop Guidelines for the Southeastern U.S., advocate plant populations for vining cultivars of approximately 725 to 1465 plants/acre (1790–3620 plants/ha). Our results with `Howden Biggie', a cultivar that produces larger pumpkins than most other vining cultivars grown for the wholesale market, indicate that producers of vining cultivars should use plant populations from the lowest values of these recommendations or use even lower values. Our results also indicate that growers can control size and weight of pumpkins by varying plant population, with increasing populations resulting in a slight decrease of size and weight.

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Charles S. Krasnow and Mary K. Hausbeck

winter squash and pumpkin ( Cucurbita sp.) production have exceeded 50% ( Babadoost, 2000 ; Isakeit, 2007 ; Meyer and Hausbeck, 2013a ). The pathogen overwinters in the soil and plant residue as long-lived oospores that serve as primary inoculum. The

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Elsa S. Sánchez, Thomas M. Butzler, Lee J. Stivers, Timothy E. Elkner, Steven M. Bogash, R. Eric Oesterling, and Michael D. Orzolek

Butternut, acorn, and buttercup/kabocha winter squash (Cucurbita sp.) cultivars were evaluated in a conventional system in central, southeastern, and southwestern Pennsylvania in 2010–11. Results from individual locations were used to create statewide recommendations, which are also relevant for the mid-Atlantic U.S. region. Additionally, butternut and acorn cultivars were evaluated in an organic system in central Pennsylvania. In a conventional system, butternut cultivars JWS6823, Betternut 401, Quantum, and Metro are recommended based on equal or higher marketable yield than the standard Waltham Butternut. Acorn squash cultivars that performed equally to or better than the standard, Tay Belle, were Table Star, Harlequin, and Autumn Delight. In the kabocha/buttercup category, ‘Sweet Mama’ and ‘Red Kuri’ had marketable yields not different from the standard ‘Sunshine’ in central and southeastern Pennsylvania. In the organic system, butternut cultivars JWS6823, Betternut 401, and Metro all had marketable yields not different from the standard Waltham Butternut. For acorn cultivars, Celebration yield did not differ from the standard Table Queen.

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James D. McCreight, Hsing-Yeh Liu, and Thomas A. Turini

Cucurbit leaf crumple geminivirus (CuLCrV) is transmitted by sweet-potato whitefly (Bemisia tabaci) biotype B (SPWF-B) and occurs on cucurbits in Arizona, California, Texas, and Mexico. This virus is identical to Cucurbit leaf curl virus, and their symptoms are similar to Squash leaf curl virus on squash (Cucurbita sp.) and Melonleaf curl virus on melon (Cucumis melo L.). Melon has been reported to be either susceptible to CuLCrV, or to have the ability to recover from infection. Twenty-three melon cultigens were inoculated with CuLCrV in greenhouse tests using SPWF-B. Eighteen of the cultigens tested were highly susceptible to CuLCrV (≥60% infected plants) and generally exhibited pronounced CuLCrV symptoms: `Amarillo', `Edisto 47', `Esteem', `Fuyu 3', `Impac', `Moscatel Grande', `Negro', `Perlita', PI 234607, PI 236355, PI 414723, `PMR 5', `Seminole', `Sol Dorado', `Sol Real', `Top Mark', `Vedrantais', and WMR 29. Five cultigens were resistant to CuLCrV (<40% infected plants that exhibited restricted, mild symptoms): MR-1, PI 124111, PI 124112, PI 179901, and PI 313970. Symptoms abated with time in both groups although infected plants remained positive for the virus. Ten of the cultigens (`Edisto 47', `Fuyu 3', `Impac', MR-1, PI 124112, PI 313970, PI 414723, `PMR 5', `Top Mark', and WMR 29) were included in field tests in 2003 and 2004 that were naturally infected with CuLCrV. With the exception of PI 414723, the greenhouse and field data were consistent for reaction to CuLCrV.

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Marilyn Rivera-Hernández, Linda Wessel-Beaver, and José X. Chaparro

Squash and pumpkins (Cucurbita sp.) are important contributors of beta-carotene to the diet. Consumers of tropical pumpkin and butternut squash (both C. moschata Duchesne) prefer a deep orange mesocarp color. Color intensity is related to carotene content. Among the five domesticated Cucurbita species, C. moschata and C. argyrosperma Huber have a close relationship. In crosses between these two species, fertile F1 plants can be easily obtained when using C. argyrosperma as the female parent. This research studied the relationship between and within C. moschata and C. argyrosperma by sequencing three genes in the carotenoid biosynthesis pathway and generating gene trees. Genotypes used in the study differed in flesh color from very pale yellow to dark orange. In some cases, haplotypes were associated with a particular mesocarp color. Further study of these types of associations may improve our understanding of color development in Cucurbita. The frequency of single nucleotide polymorphisms (SNPs) in the sequenced fragments was low. There were more SNPs and more heterozygotes among C. moschata accessions than among C. argyrosperma accessions. Haplotypes of the outgroups (C. ficifolia C.D. Bouché and C. maxima Duchesne) were always distinct from C. moschata and C. argyrosperma. These later species had both distinct haplotypes and shared haplotypes. Haplotypes shared among species tended to be maintained in the same branch of the phylogenetic tree, suggesting either gene flow between the species or a common ancestral gene. Both explanations suggest a close genetic and evolutionary relationship between C. moschata and C. argyrosperma.

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Jorge Pérez-Arocho and Linda Wessel-Beaver

Melonworm (Diaphania hyalinata) is one of the most damaging pests of squash and pumpkin (Cucurbita sp.) in tropical/subtropical regions of the Americas. In order to identify sources of resistence to melonworm, we evaluated 345 accessions of C. moschata, including both tropical and temperate types, originating from the Americas, Europe, Asia, and Africa. C. argyrosperma (65 accessions) was also evaluated. Accessions were field tested in five single-plant complete blocks planted over a 9-month period in Isabela, P.R. Each plant was evaluated for foliar damage (0–4 scale) at 3 and 6 weeks. Larval counts were made on a five-leaf sample at 8 weeks. Accessions were classified for degree of leaf mottling and pubescence. Differences among accessions were found for foliar damage and number of larva, but ranking of accessions varied, depending on the criteria used to measure resistance. In order to establish independent culling levels, we considered the lower 30% of accessions for each trait. The upper limit was ≤0.42 for foliar damage at 3 weeks, ≤0.50 damage at 6 weeks, and ≤1.25larva/plant. This led to the selection of 34 resistant accessions. We used a similar technique to identify the most susceptible accessions. The susceptible accessions will be used as a control group when the 34 selections are further evaluated. Within C. moschata, accessions with either green leaves or less pubescence had less leaf damage and fewer larva than accessions with mottled leaves or more pubescence. As a group, C. argryosperma accessions were more susceptible, and nearly all had mottled leaves and little pubescence. Untested accessions with green leaves and/or little pubescence might yield additional sources of resistance to melonworm.

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Jason Prothro, Katherine Sandlin, Hussein Abdel-Haleem, Eleni Bachlava, Victoria White, Steven Knapp, and Cecilia McGregor

( Cucurbita sp.) ( Robinson and Decker-Walters, 1997 ). Watermelon production is mainly focused on the edible flesh of the fruit, placing a premium on fruit characteristics. Seed size is important because watermelon breeders aim to develop hybrid cultivars

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Elsa S. Sánchez, Ermita Hernández, Mark L. Gleason, Jean C. Batzer, Mark A. Williams, Timothy Coolong, and Ricardo Bessin

( Cucurbita sp.), and zucchini ( Cucurbita pepo ) ( McGrath, 2001 ). On conventional farms, insecticides are the primary tool for bacterial wilt control. Recommendations for timing of insecticide applications in conventional production vary from calendar