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Qi Zhang, Enda Yu, and Andy Medina

Cucurbita pepo , C. moschata , and C. maxima are the most economically important three (out of five) cultivated species within the Cucurbita genus that include squashes, pumpkins, and gourds, which represent several species in the same crop

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Donald E. Irving, Glen J. Shingleton, and Paul L. Hurst

Extractable activities of α-amylase, β-amylase, and starch phosphorylase were investigated in order to understand the mechanism of starch degradation in buttercup squash (Cucurbita maxima Duchesne ex Lam. `Delica') with the ultimate goal of improving the conversion of starch into sweet sugars. During rapid starch synthesis (0 to 30 days after flowering), extractable activities of α-amylase and β-amylase were low, but those of starch phosphorylase increased. After harvest, during ripening at 12 °C, or in fruit left in the field, activities of α-amylase and β-amylase increased. Starch contained 20% to 25% amylose soon after starch synthesis was initiated and until 49 days after harvest irrespective of whether the crop remained in the field or in storage at 12 °C. Maltose concentrations were low prior to harvest, but levels increased during fruit ripening. Data suggest starch breakdown is hydrolytic in buttercup squash, with α-amylase being the primary enzyme responsible for initiating starch breakdown.

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Jake Uretsky and J. Brent Loy

In recent decades, F 1 hybrids in the genus Cucurbita have increasingly gained prominence over open-pollinated varieties, particularly in summer squash, ornamental pumpkin and acorn cultivars of C. pepo L. and kabocha cultivars of C. maxima

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Gabriela Verdugo Ramírez, Mauricio Cisternas Baez, Ursula Steinfort, Hermine Vogel, and Rosa Cueto-Ewoldt

Chilean species. One of the most important outcomes of these breeding projects was the development of the first intergeneric hybrid, Chlorogavilea ‘Máxima’ obtained from Chloraea crispa Lindl., and Gavilea longibracteata (Lindl.) Sparre ex Navas

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Michelle Wirthensohn

’, ‘Carina’, ‘Maxima’, ‘Mira’, ‘Rhea’, and ‘Vela’ all outperform the benchmark cultivar Nonpareil in yield, with four being self-fertile. The earlier flowering cultivars offer a replacement for ‘Price’, and the later flowering cultivars offer a replacement

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D.Q. Fang and M.L. Roose

`Chandler' pummelo [Citrus maxima (Burm.) Merrill] was found to be citrus tristeza virus (CTV)–resistant. The inheritance of this resistance in 84 progeny of two crosses derived from `Chandler' pummelo and trifoliate orange [Poncirus trifoliata (L.) Raf.] was controlled by a single dominant gene designated Ctv2. Progeny analysis of four molecular markers closely linked to the Ctv gene, which confers resistance to CTV in trifoliate orange, demonstrated that Ctv2 was an independently assorting gene from Ctv.

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T.J.K. Radovich*, R.C. Pratt, L.A. Duncan, N. Welty, and M.D. Kleinhenz

Cucurbita maxima and C. pepo are difficult to hybridize, and it was our objective to generate F1 hybrids between ornamental cultivars of the two species. C. maxima `Lakota' and C. pepo `Jack O'Lantern'; and `OZ'; were selected as parents. `Lakota' (L) is an heirloom, hubbard-type cultivar producing pear-shaped, red-orange fruit with dark green mottling, `Jack O'Lantern'; (J) is an open-pollinated Halloween-type pumpkin cultivar and `OZ' is a Halloween-type hybrid. Sixteen plants of each cultivar were greenhouse-grown in a CRB design during the period July-Sept. 2003. Interspecific crosses were made in both directions, with intraspecific crosses (J × O) and selfs (L) serving as controls. Fruits were harvested about 20 d after pollination. Embryos were excised under aseptic conditions and grown on either full strength Murashige and Skoog (MS) media with 6% sucrose (S6), full strength MS media with 6% maltose (M6), or half strength MS media with 3% sucrose (S3). Fruit set was generally greater in the intraspecific crosses (33%) and selfs (67%) than in the interspecific crosses (15 %), with the notable exception of the interspecific combination L × J (85% fruit set). Embryos of interspecific and control crosses were about 1.5mm and >1cm long, respectively. Hypocotyl and root growth 10 d after plating was better on S3 (3.2 and 1.7 cm) than on S6 (1.6 and 0.25 cm) or M6 (0.35 and 0 cm), and a greater number of functional hybrids were obtained from embryos grown on S3 (6 plants) than on S6 (2 plants) or M6 (2 plants). The interspecific plants were backcrossed to one of the parents and novel combinations of shape, color and variegation in hybrid fruit were observed.

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María Ferriol, Belén Picó, and Fernando Nuez

Cucurbita maxima Duch. is one of the most morphologically variable cultivated species. The Center for Conservation and Breeding of the Agricultural Diversity (COMAV) holds a diverse germplasm collection of the Cucurbita genus, with more than 300 landraces of this species. Morphological and molecular characterization are needed to facilitate farmer and breeder use of this collection. With this aim, the morphological variation of a collection of 120 C. maxima accessions was evaluated. The majority of these accessions originated from Spain, which has acted as a bridge since the 16th century for spreading squash morphotypes between the Americas and Europe. South American landraces (the center of origin of this species) were also included. Eight morphological types were established based on this characterization and previous intraspecific classifications. A subset of these accessions, selected from these classification and passport data, was employed for molecular characterization. Two marker types were used; sequence related amplified polymorphism (SRAP), which preferentially amplifies open reading frames (ORF), and amplified fragment length polymorphism (AFLP). In the main, SRAP marker analysis grouped accessions in accordance to their type of use (agronomic traits) and AFLP marker analysis grouped accessions as to their geographical origin. AFLP marker analysis detected a greater genetic variability among American than among Spanish accessions. This is likely due to a genetic bottleneck that may have occurred during the introduction of squash into Europe. The disparity of the results obtained with the two markers may be related to the different genome coverage which is characteristic of each particular marker type and/or to its efficiency in sampling variation in a population.

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Yang Chen, Xianzhi Zhou, Yongsheng Lin, and Yucan Zhang

area of 400,000 hm 2 and yielding more than 700 million tons. Furthermore, China is the world’s largest producer of pumpkins ( Yang et al., 2016 ; Zhao et al., 2009 ). Cucurbita moschata , Cucurbita maxima, and C. pepo are the main species in

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Steven C. Wiest and Roth E. Gaussoin

The following model simulates hourly temperature fluctuations at 6 Kansas stations:
\batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \[T_{h}=\frac{(T_{x}-T_{n})}{2}\left[\mathrm{exp}\left(\frac{0.693h}{DL_{M}}\right)-1\right]+T_{n};{\ }0{\leq}h{\leq}DL_{M}\] \end{document}
\batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \[T_{h}=\frac{(T_{x}-T_{n})}{2}\left[1+\mathrm{sin}\frac{{\pi}(h-DL_{M})}{2(23-DL_{M})}\right]+T_{n};{\ }DL_{M}{\leq}h{\leq}23\] \end{document}
where h = time (hours after sunrise), DLM = 20.6 - 0.6 * daylength (DL), Th = temperature at time h, and TX and Tn = maximum and minimum temperature, respectively. Required inputs are daily TX and Tn and site latitude (for the calculation of DL). Whereas other models have been derived by fitting equations to chronological temperatures, this model was derived by daily fitting of hourly temperatures sorted by amplitude. Errors from this model are generally lower, and less seasonally biased, than those from other models tested.