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John R. Duval and Elizabeth Golden

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D. Scott NeSmith and John R. Duval

During 1998 and 1999, `Genesis' triploid watermelons [Citrullus lanatus (Thunb.) Matsum. & Nak.] were grown in large blocks with a single row of the diploid `Ferarri' planted as a pollinizer in the middle. A once-over harvest each year was made in harvest lanes 0, 1.5, 3.0, 4.5, 6.0, 7.5, and 9.0 m perpendicular distances from the pollinizer row. Individual fruit were weighed and counted. Data from both years indicated a similar distribution of triploid fruit with respect to distance from the pollinizer row. The greatest number of triploid fruit per unit land area was in the harvest row 3.0 m from the pollinizer row. When distance from the pollinizer row was 6.0 m or greater, triploid fruit numbers diminished substantially. Yield estimates made each year using the fruit density data suggested that a 1 pollinizer: 4 triploid ratio gave the maximum total triploid fruit yield per hectare for 1.5-m row spacings. These results should prove useful in designing field planting strategies to optimize triploid watermelon production.

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D. Scott NeSmith and John R. Duval

Transplants for both vegetable and floral crops are produced in a number of various sized containers or cells. Varying container size alters the rooting volume of the plants, which can greatly affect plant growth. Container size is important to transplant producers as they seek to optimize production space. Transplant consumers are interested in container size as it relates to optimum post-transplant performance. The following is a comprehensive review of literature on container size, root restriction, and plant growth, along with suggestions for future research and concern.

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John R. Duval and D. Scott NeSmith

Age and cell size can have various effects on subsequent transplant production. The interaction of the two have not been studied in triploid watermelon [Citrullus lanatus (Thunb.) Matsum & Nakai]. Seedless watermelon production is costly due to high seed prices, therefore it is necessary to optimize transplant performance in the field, and it is often thought that triploid watermelons are less hardy than their diploid counterparts. A 3 × 3 factorial design was established for 2 years to determine the effects of cell sizes 1.5, 3.4, and 7.9 inch3 (25, 56, and 130 cm3) and transplant age (4, 6, and 8 weeks) on the triploid watermelon `Genesis'. The diploid cultivar `Ferrari' was also planted for comparison. Seedling survival was affected by transplant age in 1997, and by cell size in 1998. Early main vine growth showed significant interaction between transplant age and cell size, with older transplants grown in the largest cells producing the longest vines. Early yield of 6-week-old transplants of `Genesis' was higher than 4- or 8-week-old transplants in 1997. Eight-week-old transplants of `Ferrari' outperformed younger transplants in 1997 and 1998. Results show that `Genesis' triploid watermelon transplants could be handled similarly to the diploid `Ferrari' without consequence.

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D. Scott NeSmith and John R. Duval

During 1998 and 1999, `Genesis' triploid watermelons were grown in large blocks with a single row of the diploid `Ferarri' planted as a pollinizer in the middle. A once-over harvest of triploid watermelons was made each year in harvest lanes 0-, 1.5-, 3.0-, 4.5-, 6.0-, 7.5-, and 9.0-m perpendicular distances from the pollinizer row. Individual fruit were weighed and counted. Data from both years indicated a similar distribution of triploid fruit with respect to distance from the pollinizer row. The greatest number of triploid fruit per unit land area was in the harvest row 3.0 m from the pollinizer row. When distance from the pollinizer row was 6.0 m or greater, triploid fruit numbers diminished substantially. Yield estimations made each year using the fruit density data suggested that a 1 pollinizer: 4 triploid ratio gave the maximum total triploid fruit yield per hectare for 1.5-m row spacings. These results should prove useful in designing field planting strategies that seek to optimize triploid watermelon production.

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John R. Duval and D. Scott NeSmith

Seeds of triploid watermelons [Citrullus lanatus (Thunb.) Matsum & Nakai] often germinate poorly, which prevents adequate stand establishment in both field and greenhouse environments. Methods of improving germination and emergence of these expensive seeds would reduce overall risk to growers, thus increasing the crop's market prominence. Seeds of `Genesis' triploid watermelon were subjected to three treatments: 1) seedcoat removal; 2) clipping the seedcoat opposite the radicle end; or 3) no seedcoat alteration; and were germinated on agar in the presence of a 0%, 1%, 2%, 4%, or 8% aqueous H2O2 at constant 28 °C in the dark. Seedcoat removal, clipping, and all levels of H2O2 increased final germination percentages relative to the control (no seedcoat alteration, no H2O2) by as much as 70%. Hydrogen peroxide levels >2% resulted in severe injury to germinating seeds. These findings suggest that germination barriers of triploid watermelon are seedcoat related, and that seedcoat alteration and H2O2 can overcome these barriers.

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John R. Duval and D. Scott NeSmith

Production of triploid watermelon [Citrullus lanatus (Thunb.) Matsum & Nakai] transplants is hindered by poor, inconsistent emergence, and frequent seed coat adherence to cotyledons. Seed coat adherence leads to weakened and slow growing plants. High seed costs, coupled with stand establishment problems, discourages transplant producers from growing this crop. Improvement of triploid watermelon emergence will lessen financial risks to growers and transplant producers and will provide a more reliable production system. Mechanical scarification was evaluated as a means to overcome inconsistent emergence and seed coat adherence. Seeds of `Genesis' triploid watermelon were placed in a cylinder with 100 g of very coarse sand (1.0 to 2.0 mm diameter) and rotated at 60 rpm for 0, 6, 12, 24, and 48 hours in a series of experiments. Number of emerged seed was recorded daily, to obtain emergence dynamics. No significant differences were observed in seed coat adherence among treatments. The longest duration of scarification However, enhanced emergence as compared to the control in three of four experiments. These data support earlier suggestions that a thick or hard seed coat is a factor contributing to poor germination and emergence of triploid watermelons.

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John R. Duval and D. Scott NeSmith

Production of triploid watermelon [Citrullus lanatus (Thunb.) Matsum & Nakai] transplants is hindered by low and nonuniform emergence, and seedcoat adherence. Seedcoat adherence leads to weakened and slow-growing plants. High seed costs are prohibitive to many transplant growers. Improvement of emergence would lower financial risks to growers and transplant producers. Mechanical scarification was examined as a means to decrease the impact of both problems. Seeds of `Genesis' triploid watermelon were placed in a cylinder with 100 g of very coarse sand and rotated for 6, 12, 24, and 48 hours at 60 rpm. Nontreated seeds were used as a control. Data were taken daily on emergence and seedcoat adherence. The experiment was repeated at three temperature regimes. No significant differences were observed in seedcoat adherence. Scarification, however, did significantly improve emergence under test conditions.

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John R. Duval*, Elizabeth Golden, Julia Reekie and Peter Hicklenton

Bare-root transplants received from high latitude nurseries for Florida production have limited root systems, very long petioles and wilt soon after planting. Further dessication occurs when leaves come in contact with black plastic mulch used in the annual production system. Conventional irrigation practices for the establishment of bare-root transplants of strawberry consist of overhead water application for at least 8 hours/day for 10-14 days after planting. Plant growth regulators (PGRs) have been used to modify the growth characteristics of many plants species. A split-block experiment was implemented at the GCREC-Dover, Dover Fla., to determine the effect of the use Prohexidione-Ca (PC) and IBA [(indole-3) butyric acid] on growth, yield and establishment of strawberry. Main blocks consisted of over head establishment irrigation for 4, 8, and 12 days, and sub-plots consisted of treatments of PC applied in the nursery at a rate of 62.5 mg·L-1 2, 4, or 6 weeks before digging, PC applied in the nursery at 31.25 mg·L-1 2 weeks before digging, a root dip of transplants in 100 mg·L-1 IBA just prior to transplanting. The experiment was conducted for four growing seasons. Data were recorded for marketable yield, number of marketable berries (>10g), and disease incidence. Significant differences were detected for duration of establishment irrigation and growth regulator treatment. No interaction was shown between establishment irrigation and growth regulator treatment.