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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

Botwright, T. Mendham, N. Chung, B. 1998 Effect of density on growth, development, yield and quality of kabocha ( Cucurbita maxima ) Austral. J. Expt. Agr. 38 195 200 Broderick, C.E. 1982 Morpho-physiological factors affecting plant productivity in bush and

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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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Matthew B. Bertucci, David H. Suchoff, Katherine M. Jennings, David W. Monks, Christopher C. Gunter, Jonathan R. Schultheis, and Frank J. Louws

.05. SG, self-grafted; NG, nongrafted; ISH, interspecific hybrid squash derived from the cross Cucurbita maxima × C. moschata ; 1 g = 0.0353 oz. ANOVA of root system characteristics determined the main effects of rootstock, species, and harvest date

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Rosa Marina Arvayo-Ortiz, Sergio Garza-Ortega, and Elhadi M. Yahia

Winter squash is grown in the Northwest of Mexico for export to distant markets with risk of produce loss. A study was conducted to investigate its postharvest behavior as affected by hot water (50°C) for 0, 3. 6, 9 and 12 min, and stored at 10 or 20°C with 75% RH for 4, 8, and 12 weeks. The highest weight loss (11.35%) was in fruits without hot water treatment stored at 20°C for 12 weeks; at this temperature the weight loss was 3.65, 7.18, and 10.19% in the 4, 8 and 12 week storage period, respectively. At 10°C the weight loss was 3.41, 6.83 and 7.56% for the same period. Chlorophyll content decreased as temperature and storage period increased. β-carotene content showed no change at 10°C, but slightly increased after 8 and 12 weeks at 20°C. Fruits showed decay by Rhizopus and Aspergillus. Weight loss, chlorophyll content, and decay were not affected by length of hot water treatment. General appearance was better in fruits stored at 10°C than at 20°C.

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Donald E. Irving, Paul L. Hurst, and Jonathan S. Ragg

During this study, we divided the developmental growth pattern of buttercup squash into three phases: 1) early growth, from flowering up to 30 days after flowering; 2) maturation, from 30 days until 60 days after flowering (or harvest); and 3) ripening, from 60 days (or harvest) until ≈100 days after flowering. Harvest occurred at 48 days after flowering. Fruit growth (expansion), starch, and dry matter accumulation were largely completed during early growth, and there was a progressive decline in the respiration rate. Extractable activities of acid and alkaline invertases, sucrose synthase, alkaline α-galactosidase, and sucrose phosphate synthase (assayed with saturating substrates) were high initially but declined markedly during this phase. Glucose, fructose, and low concentrations of raffinose saccharides were present, but no sucrose was detected. During maturation, starch and dry matter remained nearly constant and sucrose began to accumulate. During ripening, starch was degraded, sucrose synthase activity was significant but relatively constant, sucrose phosphate synthase activity increased, and sucrose continued to accumulate.

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Jennifer Wetzel and Alexandra Stone

://> Bisognin, D.A. 2002 Origin and evolution of cultivated cucurbits Cienc. Rural 32 4 1190 1198 Botwright, B. Mendham, N. Chung, B. 1998 Effect of density on growth, development, yield and quality of kabocha ( Cucurbita maxima ) Austral. J

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Benjamín Moreno, Cristián Jacob, Marlene Rosales, Christian Krarup, and Samuel Contreras

Grafting of seedlings is a technique used for watermelon (Citrullus lanatus) production in many countries. Because of higher costs involved, the use of grafted seedlings can only be recommended if it provides clear biological and economic benefits. Since rootstock performance is influenced by compatibility with the cultivar, the existing disease pressure, and climatic conditions, it is necessary to evaluate rootstocks with current cultivars to appraise possible benefits in a given area. Two experiments were carried out in two consecutive seasons with the objective of evaluating the benefits of grafting under Chilean conditions. The rootstocks used were ‘Marathon’ (Cucurbita maxima × Cucurbita moschata) and ‘Macis’ (Lagenaria siceraria) with different scions, including some seedless cultivars. In both experiments, grafted plants increased their yield compared with nongrafted plants (136% and 159% in Expts. 1 and 2, respectively). This effect was due to an increased number of fruit per plant (P < 0.01), and the weight gain of the fruit (P < 0.01). Plants presented with fusarium wilt [Fusarium oxysporum f. sp. niveum (FON)] in both experiments, which seemed to be the main limitation for nongrafted plant production. In the evaluation of quality attributes [soluble solid concentration (SCC), firmness, color, polar diameter, equatorial diameter, and rind thickness], positive effects were observed in the fruit of grafted plants. For the conditions of these experiments, the increase in yield of grafted plants would be associated with an economic benefit that exceeds its additional cost.

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Yang Chen, Xianzhi Zhou, Yongsheng Lin, and Lina Ma

To study the effects of nitrogen (N), phosphorus (P), and potassium (K) fertilizers on the yield of ‘Jianbao’ pumpkin (Cucurbita maxima Duch), we conducted experiments using the “3414” optimal design scheme in Dehua County, Quanzhou, Fujian, China. Overall, three fertilizer factors (N, P, K) were tested with four fertilization levels (level 0, no fertilizer; level 1, 0.5-times the typical fertilizing amount; level 2, typical fertilizer application; level 3, 1.5-times the typical application), with a total of 14 different fertilization treatments. Based on the results of this study, a corresponding fertilization performance model was established to provide a practical basis for ensuring highly efficient cultivation of pumpkin in the field. Our results showed that the experimental data could not be fitted with a ternary quadratic polynomial fertilizer model, but that it could be fitted with a single-variable quadratic fertilizer model. According to the fitted model, pumpkin yield first increased and then decreased with the increasing amount of N, P, and K used. We identified significant regression relationships between ‘Jianbao’ pumpkin yield and the amount of N, P, and K in the fertilizer. Finally, based on the single-variable quadratic fertilizer model, we suggest that the quantities of N, P, and K fertilizer used for growing 1 ha of ‘Jianbao’ pumpkin should be 390.5, 213.8, and 371.3 kg, respectively.