squash used for pies, jack-o'lanterns, or stock feed” ( Robinson and Decker-Walters, 1997 ). Pumpkin encompasses various Cucurbita L. species such as Cucurbita pepo L., C. maxima Duchesne, C. moschata Duchesne, and C. argyrosperma C. Huber
A. Lane Rayburn, Mosbah M. Kushad and Wanisari Wannarat
Vincent Njung’e Michael, Yuqing Fu and Geoffrey Meru
and Lamour, 2004 ; Sanogo and Ji, 2012 ). Cucurbita moschata Duchesne, Cucurbita maxima Duchesne, and Cucurbita pepo L. are the three main squash species cultivated in the United States, with the latter being the most economically important
Njung’e Vincent Michael, Pamela Moon, Yuqing Fu and Geoffrey Meru
markers assayed ( Murovec, 2015 ). Table 1. Genetic parameters revealed by 30 simple sequence repeat (SSR) markers on 16 Cucurbita pepo accessions resistant to Phytophthora crown rot and eight susceptible cultivars. Variation in discrimination power of
Les D. Padley Jr, Eileen A. Kabelka, Pamela D. Roberts and Ronald French
; Tian and Babadoost, 2004 ; Waldenmaier, 2004 ). Cucurbita pepo L. (pumpkin, squash, gourd) is an economically important group of the Cucurbitaceae ( Paris et al., 2003 ). Eight cultivar groups of edible-fruited domesticates of C. pepo have been
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
Michael P. Hoffmann, Richard W. Robinson, Margaret M. Kyle and Jonathan J. Kirkwyland
Seventy-six Cucurbita pepo L. cultivars and breeding lines were evaluated under field conditions for infestation levels and defoliation (leaf area consumed by beetles) by adult diabroticite beetles in 1992 and 1994. Striped and spotted cucumber beetles, Acalymma vittatum (F.) and Diabrotica undecimpunctata howardi Barber, respectively, were most common, but some western and northern corn rootworms, D. virgifera virgifera LeConte and D. barberi Smith and Lawrence, respectively, also were present. In general, pumpkin, delicata, acorn winter squash, scallop, and yellow straightneck summer squash types were the least infested and defoliated. Caserta/yellow, zucchini, caserta/zucchini, caserta, and precocious yellow straightneck types were the most infested and defoliated. The number of beetles per plant was correlated (r ≥ 0.72) with leaf defoliation and proportion of plants infested, indicating that beetle infestation is a good predictor of damage. The cultivars and breeding lines that were the least infested and defoliated can be used in breeding programs to develop desirable genotypes with reduced beetle preference. Conversely, those genotypes that were highly preferred have potential as trap crops for these beetle pests.
The effects of gene B on susceptibility to chilling injury (CI) in two types of summer squash (Cucurbita pepo L.) were investigated. Two pairs of near-isogenic lines with (BB) and without (B+ B+) gene B were included in the study: `Caserta' (B+ B+) and `Precocious Caserta' (BB) of the vegetable marrow type, and `Benning's Green Tint' (B+ B+) and `Benning's Yellow Tint' (BB) of the scallop type. Respiration and ethylene evolution at nonchilling temperature were consistently higher in marrows than in scallops. Gene B had no influence on respiratory rates at nonchilling temperatures; however, the presence of gene B enhanced the chilling-induced stimulation of respiration in both marrows and scallops. Temporal differences in the patterns of chilling-induced stimulation of ethylene evolution indicated a greater sensitivity to chilling in marrows than in scallops and in both types in the presence of gene B. Electrolyte leakage was decreased by storage at chilling temperature in both marrow genotypes and was not influenced by storage temperature in B+ B+ scallops, but was increased by storage at chilling temperature in BB scallops. Therefore, electrolyte leakage was not a good CI index for these summer squash.
Martin P.N. Gent, Zakia D. Parrish and Jason C. White
Exudation of organic acids by roots has been implicated in uptake of minerals from soil. Three cultivars within each of two subspecies of summer squash (Cucurbita pepo ssp. ovifera D. S. Decker var. ovifera and C. pepo ssp. pepo var. pepo) were grown in the field. Plants of ssp. pepo had higher concentrations of K, P, and Zn than those of ssp. ovifera. These same cultivars were grown under P sufficient and depleted conditions in hydroponics, to measure exudation of organic acids from roots. When grown in hydroponics, tissues of ssp. ovifera had similar or higher concentrations of nutrients than ssp. pepo. Therefore, differences in tissue composition of field-grown plants are likely due to differences in nutrient uptake ability, not inherent differences in tissue composition between subspecies. Phosphorus nutrition played a significant role in exudation of organic acids into the hydroponics solution. For both subspecies, P depletion resulted in exudation of more citric and succinic acid, and less oxalic and tartaric acid. Under P depletion, ssp. pepo exuded more citric acid than ssp. ovifera. When soil was eluted with solution containing root exudates, the exudates from ssp. pepo eluted more K, Mg, Fe, and Zn than did those from ssp. ovifera. Among subspecies of C. pepo, exudation of organic acids, particularly exudation of citric acid in response to P depletion, is associated with the plant's ability to accumulate more inorganic nutrients when grown in the field.
J. Brent Loy, R. Bruce Carle and Mark G. Hutton
A new leaf mutant, fused-vein, is described in Cucurbita pepo L. for use as a plant gene marker. Morphologically, the fused-vein trait is characterized by a partial fusion of the lateral leaf veins to the main central vein. Fusion begins at the distal point of the petiole and extends for 5 to 10 cm into the leaf blade, thereby delaying branching of the leaf veins and causing the dorsal leaf surface to appear puckered. The trait is expressed beginning at the fourth to sixth leaf stage and throughout vegetative growth. Preliminary inheritance data suggests a two gene, double recessive model. Data on segregation of the fused-vein trait in reciprocal F2 and backcross progenies will be obtained during the summer of 1990. This trait has been incorporated into hull-less seeded lines for use as a marker to identify rogue genotypes. Comparison of F5 sister lines with and without the fused-vein trait indicated that the trait does not affect fruit or seed yields.
R. Bruce Carle and J. Brent Loy
The expression and inheritance of the fused vein trait in Cucurbita pepo were investigated. The fused vein inbred, NH2405, was crossed to normal lines, NH614, and NHBP10. Reciprocal F1, F2, F3 and BC populations were generated and examined for leaf type segregation in field and greenhouse environments. Although the fused vein phenotype is stable in NH2405, it exhibited a continuum of expression in segregating populations. The onset of vein fusion ranged from the fourth to the tenth leaf stage and degree of fusion varied from slight (1-5 cm) to extreme (10-20 cm). Inheritance ratios varied with population, conditions of production, and direction of cross. Most segregating populations fit either a single or double recessive gene model, however, a quarter of the populations showed no or low fused vein recovery. A feasible explanation for the distorted inheritance is that the fused vein trait is a gametophytic subvital, governed by a single recessive gene, fv. Although less likely, a double recessive, subvital model cannot be ruled out.