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D.N. Maynard

Yield and quality of seedand vegetatively propagated rhubarb (Rheum rhabarbarum L.) for annual production were evaluated for four seasons. Selection of `Victoria' seedlings based on petiole color was not effective in increasing the proportion of red mature petioles. Yields from seed-propagated annual rhubarb were always higher than yields from single-bud crown divisions and from crown divisions in 1 of 2 years. Petiole color of vegetatively propagated rhubarb was always superior to that of seed-propagated rhubarb. GA applications increased early yield from single-bud divisions, but reduced petiole weight of early and total harvest of `McDonald' rhubarb. Chemical name used: gibberellic acid (GA).

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D.N. Maynard

Yield and quality of seed- and vegetatively-propagated rhubarb [Rheum rhabarbarum L.) for annual production were evaluated for 4 seasons. Field planting of transplants or crown divisions in late October or early November resulted in harvests beginning in early to late January and continuing until late April. Selection of `Victoria' seedlings based on petiole color was not effective in increasing the proportion of red mature petioles. Yields from seed-propagated annual `Victoria' rhubarb were always higher than yields from `McDonald' single-bud crown divisions and higher than yields from `McDonald' crown-divisions in one of two years. The four-year average yield for `Victoria' seed-propagated rhubarb was 20.4 Mg·ha-1 whereas `McDonald' crown-division-propagated rhubarb had a two-year average yield of 15.8 Mg·ha-1. On the other hand, petiole color of vegetatively-propagated rhubarb was always superior to that of seed-propagated rhubarb. GA applications increased early yield from `McDonald' single-bud divisions, but reduced early and total harvest petiole weight.

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G. W. Elmstrom and D. N. Maynard

Watermelon, Citrullus lanatus (Thunb.) Matsum. & Nakai, requires insects, most commonly honey bees, for pollination and fruit set. The transfer of an adequate amount of pollen is essential to ensure optimum fruit set, size, and shape. To encourage bee visits and the transfer of pollen, two applications of Bee-Scent*, a bee attractant, at 2.47 liter·ha-1 were made to watermelon on five farms in central and southwest Florida. Honey bee, Apis melifera L., activity was monitored for two days following each application and yield and fruit quality were determined. On only a few occasions was increased honey bee activity noted. Application of bee attractant increased total yield in one field in central Florida and resulted in an increase in early yield at all three locations in southwest Florida. Soluble solids content of mature fruit was not directly affected by treatment. Treatment increased the seed content of fruit from three of five farms.

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D.N. Maynard and G.W. Elmstrom

Fruit set of 'Crimson Sweet', 'Jubilee II', 'King of Hearts', 'Mickylee', and 'Sangria' watermelons was studied in Florida, In 1991 and 1992 seasons at Bradenton and Leesburg, In 1991, fruit set at Bradenton occurred primarily from 7-10 October. At Leesburg, fruit set in at least one of the four varieties occurred over 19 days. However, there were flushes of fruit setting 25-28 September and again 5-7 October. Fruit set over the entire season ranged from 11 to 16% at Leesburg and between 17 and 20% at Bradenton. In 1992, fruit set occurred primarily between 11 and 17 October at both locations. Fruit set for the entire season ranged from 16 to 21% at Bradenton and 22 to 31% at Leesburg. The effects of bee attractants on watermelon fruit yield were studied in Manatee (Bradenton) County in fall 1991 (Bee Scent) and in Manatee and Lake (Leesburg) counties in spring 1992 (Bee-Here). Bee attractants did not significantly affect yield in three of four experiments. In the fourth experiment, early yield and average fruit weight for the entire season were increased significantly following application of the bee attractant.

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D. N. Maynard and G. W. Elmstrom

Mature seeds occur occasionally in triploid watermelon fruit. In one trial, the average number varied from 0.3 to 28.7 seeds per fruit in 30 entries and from 0.5 to 8.6 seeds per fruit in the cultivars within this group. The frequency of mature seed in triploid fruit with the same tetraploid parent ranged from 0.3 to 3.0 and from 1.25 to 5.0 seeds per fruit in triploid fruit having the same diploid parent. Tetra A, with 151 seeds per fruit, produced triploids with 6 seeds per fruit; whereas Tetra B, with 74 seeds per fruit produced triploids with only 1.3 seeds per fruit. Date-of-flowering of diploid watermelon cultivars used as pollenizers for triploids affected maturity date of the triploids. Icebox-types that flower early produced higher early yields of triploid fruit; whereas standard cultivars that flower later produced higher yields late in the season.

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G.W. Elmstrom, F. McCuistion Jr. and D. N. Maynard

Watermelon varieties were evaluated for hollowheart (HH) at Bradenton, Leesburg, and Quincy, Fla. HH varied with location, variety, and season. Among icebox varieties, `Sugar Baby', `Baby Gray', and SSDL had less HH than `Tiger Baby', `Minilee', and `Mickylee'. Among standard varieties, `Sangria' and `Jubilee II' had less HH than `Crimson Sweet' and `Royal Sweet'. In 1990, HH was more severe at Quincy than at Bradenton or Leesburg, but the ranking of seedless entries was similar among the locations. HMX 7928, `Nova', `Tycoon', and `Millionaire' had least HH, and `Jack of Hearts', `Ssupersweet 4073', `Ssupersweet 5344', and `King of Hearts' had the most HH. `Jack of Hearts' and `Crimson Sweet' fruit were cut and evaluated in Spring 1993 at 5, 12, 19, 26, and 33 days after anthesis. Incidence of HH was low in 5- and 12-day-old fruit, increased in fruit that were 19 or 26 days old, and did not increase in older fruit. About one-third of fruit from both varieties had some HH. Among the seven entries in another test in Spring 1993, `Tri-X-313' had the least HH and `Crimson Sweet', `Jack of Hearts', and `Jubilee II' had the most.

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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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Alvaro O. Pacheco, G.J. Hochmuth, D.N. Maynard, A.A. Csizinszky and S.A. Sargent

Optimum economic yield is produced when nutrients in the proper amounts are supplied to the crop. Crop nutrient requirements (CNR) of essential elements have been determined for the major vegetables produced in Florida. However, for minor crops, such as muskmelon, little research has been conducted to determine the CNR, especially potassium. In many vegetables, yield has responded to increasing K rates when other elements were not limiting. Our objective was to determine the K fertility requirement for optimum yield of muskmelon and to evaluate the Mehlich-1 soil test calibration for soil testing low in K (<20 mg·kg–1). Experiments were conducted in the spring and fall seasons of 1995. Potassium at five rates (0, 56, 112, 168, and 224 kg·ha–1) was injected weekly, approximating the growth curve of `Galia' and `Mission'. There were significant yield responses to K fertilization for both cultivars during both seasons. During spring, average marketable yield was 14.5, 26.1, 31.9, 31.5, and 36.3 Mg·ha–1 and for fall, average marketable yield was 15.8, 32.9, 37.8, 37.2, and 36.4 Mg·ha–1 for the previously described K treatments, respectively. The cultivar response for both seasons was described by a linear-plateau model. In spring, yield was maximized with K at 116.8 and 76.3 kg·ha–1 for `Galia' and `Mission', respectively. In fall, K at 73.3 and 68.3 kg·ha–1 produced the peak response for the same cultivars. These results indicate that maximum yield of muskmelon in Florida can be obtained at considerably less K than the current recommendation of 140 kg·ha–1.

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D.N. Maynard, G.W. Elmstrom, J.K. Brecht and L. Wessel-Beaver

Bush and short-vined calabazas [Cucurbita moschata (Duchesne) Poir.] derived from crosses of `Bush Butternut' with `La Primera' and `La Segunda' followed by several generations of selection and self pollination, are quite uniform in plant and fruit characteristics. Likewise, selfing and selection of vining cultigens has resulted in uniform vine and fruit characteristics. Hybrids between bush/short-vined and vining lines usually retain the plant habit of the bush/short-vined parent, and produce higher yields of fruit with thicker and better-colored flesh than open-pollinated cultigens. Hybrid bush/short-vined calabazas are earlier, have more concentrated fruit set, and utilize space better than open-pollinated cultigens. Commercial seed of hybrids is likely to be more readily available than seed of open pollinated cultigens.

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D. N. Maynard, G. W. Elmstrom, L. Wessel-Beaver and T. G. McCollum

The flowering habit and yield potential of seven calabaza [Cucurbita moschata (Duchesne), Poir.] genotypes were studied in the fall 1991 season. Earliest flowering and mature fruit were produced on bush plants developed from `Burpee Butterbush'. Time of flowering and distance from the crown was intermediate in time in the Florida developed varieties `La Primera' and `La Segunda' and latest in the Puerto Rican developed entries `Borinquen', Linea C Pinta, and Soler. Highest yields were produced by `La Primera' and `La Segunda', whereas, lowest yields were produced by the bush lines because of very small fruit size. Fruit size of `Borinquen' and Linea C Pinta was mostly in the desirable range of 2.3 to 4.5 kg. Most `La Primera' and `La Segunda' fruit were round, `Borinquen', Linea C Pinta, and Soler fruit were flat, and the bush lines produced variable shaped fruit. Further backcrossing to round types is required to overcome the problem of small fruit size and variable fruit shape in the bush lines.