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University of Arizona
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College of Agriculture and Life Sciences |
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Impact Nugget Issue Increasing numbers of vegetable growers are purchasing their transplants from specialized transplant producers. There is a growing nationwide interest in use of high quality grafted seedlings for greenhouse tomato production, but the source of grafted tomato seedlings is still limited in the United States. For example, greenhouse tomato growers in Arizona must purchase grafted seedlings from Canadian propagators, thus risking deterioration of transplants during transportation. Over the past several years, abnormal fruit development has been observed for the first truss (fruit set), attributed to the rigors of long distance transportation. Further, Arizona greenhouse tomato growers have observed that transportation conditions, coupled with the status of flower development during transportation, and planting conditions after transportation, influence flower abortion and abnormal fruit development of the first truss. Significant yield delays and losses have resulted in part because the mechanisms that cause flower drop and abnormal fruit development during long distance transportation are not well understood. What has been done? "Durinta" tomato seedlings with visible flower buds were placed for four days under various air temperatures (6 degrees, 12 degrees , or the conventional transportation temperature of 18 degrees Celsius) and light intensity (conventional darkness or dim light) to simulate transportation conditions. Plants were evaluated for visual quality, photosynthetic capacity, growth and ultimately fruit yield. Lower temperatures and illumination significantly maintained visual quality of the seedlings. Lower temperature also maintained high photosynthetic capacity of the seedlings after transportation. Growth and development of the seedlings were significantly affected at higher temperatures, resulting in significantly delayed growth and development. The first truss (fruit set) generally produces the highest yield of tomatoes, compared to that of subsequent trusses. Shortening the duration from transplanting to the first (truss) harvest is crucial to assure high annual yield of greenhouse tomatoes. The number of fruit set on the first truss was significantly reduced when seedlings were held at 18C during transportation. Delay of harvest due to the problematic abnormal fruit development and flower abortion was estimated to be one week. Overall, simulated transport at 6C under light showed the best transportability without negative impact for the four-day simulated transportation. Seedlings at 6C in darkness and at 12C under light and in darkness also showed satisfactory transportability. Seedlings at 18C exhibited serious quality deterioration of seedlings, delay in early growth and development, loss of flower buds on the first truss and yield reduction, which agrees with the fact that conventional transportation is currently limited to three days in duration. Research in 2004 also confirmed that flower abortion and yield reduction was not significant when transplants were shipped before developing visible flower buds, as the Arizona growers observed in their greenhouse as their past experiences. However, shipping in early stage of seedlings is not preferred by growers since younger seedlings take a few more weeks to the first harvest. Impact Since this strategy has been adopted, the profit to the largest Arizona greenhouse operation by improving the transport conditions for transplants and thereby assuring normal first truss development without causing delay is roughly estimated as a half million dollars per year or $3,100 per acre of greenhouse per year. There is also a significant potential benefit for transplant propagators who could extend the transportable distance and therefore the market by improving the transportability of their seedlings. Funding Contact |
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