Optimizing Long Distance Transportation Conditions for High Quality Tomato Seedlings

Enhance Economic Opportunities for Agricultural Producers
Research Year: 
2004
Issue: 

The production of high quality transplants is a critical technology that supports the success of the final crop. Healthy transplants mature predictably and yield well. In current industry practice, transplants are produced in an operation that is separate from final crop production. This recent trend is especially popular for vegetable and floriculture crops that require special techniques, such as grafting or vegetative propagation, and facilities to produce desirable transplants.

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.

Description of Action: 

Environmental conditions in temperature-controlled trailers full of grafted tomato seedlings were analyzed during a regularly scheduled two-day transportation from a Canadian propagator to Arizona growers. The goal was to understand how to optimize transportation conditions to minimize or eliminate the negative impact of transportation on the transplants and thereby on the early yield. UA researchers from the Controlled Environment Agriculture center collected information from the Canadian propagator and Arizona tomato growers on the current transportation situation and associated problems to define a hypothesis for preventing flower abortion and abnormal truss development. Simulation experiments were then conducted on campus to examine combinations of air temperature and light intensity during transportation.

"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: 

The results show that lowering air temperature to 10-12C from the conventional 18C for transplants during transportation significantly improved the development of flower and fruits of the first truss. Based on the experimental results, the largest Arizona greenhouse tomato operation adopted transportation of the grafted tomato seedlings at lower air temperatures inside the trailers (10-12 degrees C.) Immediate analysis of transplant quality and early fruit development was conducted and normal truss development was confirmed by University of Arizona researchers.

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 Agencies: 

Hatch Act; Arizona Department of Agriculture, Specialty Crop Research Program Controlled Environment Agriculture Program (CEAC); The University of Arizona

Conact Name: 
Chieri Kubota
Contact E-mail: 
Contact Address: 

The University of Arizona

Tucson, AZ 85721-0036, USA

Tel: 520-626-7937 Fax: 520-621-7186