Tomato Plant and Fruit Responses to Growth Regulator Treatment.

Tomato is one of the most important crops in the United States and the development of new techniques to increase fruit yield and quality is extremely important to improve the return on investments spent during tomato production. The objective of this work was to investigate tomato plant and fruit responses to treatment with the growth regulator VBC30053 (Valent BioSciences). Experiments in our laboratory have shown that ‘AB2’ tomato plants sprayed weekly with VBC30053 maintained higher leaf water potential, and lower stomatal conductance and water loss. The higher plant water status had a positive impact on fruit size and quality. At 40 days after pollination (DAP), fruits treated with VBC30053 were almost two times bigger than fruits treated with water (control). VBC30053 treated plants also developed and maintained higher number of functional xylem vessels in the fruit, mainly early in fruit development (until 26 DAP). The higher number of functional xylem vessels in tomato fruit treated with VBC30053 was positively correlated with a higher concentration of Ca⁺⁺ and complete control of the Ca⁺⁺ deficiency disorder, blossom-end rot (BER). It is interesting to note that VBC30053 also resulted in an increase in the expression of genes involved in Ca⁺⁺ movement into the vacuole (CAX3, CAX6, Ca-ATPase, and V-ATPase). The increase in expression of these genes may be a direct effect of VBC30053 treatment or an indirect effect in response to higher levels of Ca⁺⁺ in the fruit tissue. Independent of the mechanism involved, the increase of Ca⁺⁺ inside cellular storage organelles may in part explain the higher concentration of Ca⁺⁺ in tomato fruits treated with VBC30053, which were stronger sinks for Ca⁺⁺. The VBC30053 effects on plant water status and complete control of BER have commercial significance. It can be used to reduce plant nutrient and water requirement to increase crop yield.