ISHS Acta Horticulturae 533: VIII International Symposium on Timing Field Production in Vegetable Crops
TRIPLOID WATERMELON TRANSPLANT PRODUCTION |
| Author: | Donald N. Maynard |
| Keywords: | Citrullus lanatus, seedless watermelon |
| Abstract:
Containerized production of triploid watermelon transplants is essential because of the special conditions required for seed germination, emergence, and early plant development not found in open-field situations. Furthermore, the extra cost of seedling production is justified because triploid watermelon seeds costs are six times greater than those of diploid hybrid seeds and 60 times greater than open-pollinated diploid watermelon seeds. An abbreviated protocol for triploid watermelon transplant production follows: Excellent containerized plants are produced in 30 to 50 cm3 cells containing a sterile mix of 50 to 85% high grade peat and 35 to 50% horticultural vermiculite or horticultural perlite amended with lime, fertilizers and a wetting agent. Thiram or other approved fungicides should be applied to the seed before planting. One seed per cell should be planted about 2-cm deep with the radicle (pointed end) up to reduce seedcoat adherence to the cotyledons. The tray is watered lightly to bring the seed and mix in contact. Stacked trays should be covered with polyethylene and placed in a germination chamber at 30–35 C for about two days or until radicles are visible in the cell drainage holes. The trays are then arranged on benches in a greenhouse with day temperature 21–27C and night temperature 18–21C where temperature control can be achieved. Plants are fertilized every three days with a solution containing 50 mg.l-1 N from Ca(NO3)2 and KNO3 from cotyledon expansion until the first true leaf is fully expanded, then with a 200 mg.l-1 N solution applied every other day until the second true leaf is fully expanded, finally the fertilizer is reduced for several days before transplanting to the field. Plants are ready for transplanting when the roots are sufficiently developed to permit removal from the cell with the entire growing mix volume intact. This will require three to five weeks depending on cell size and growing conditions. Using these production methods, transplant return efficiency has been obtained from trial data since 1990 for ten varieties grown in at least five of eight years. The overall average transplant return was 79% with a range of 69% for ‘Tiffany’ to 89% for ‘Queen of Hearts’. | |
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