Controlling hormone levels optimizes tomato taste, life expectancy.

Changing the levels of a key hormone in tomatoes could lead to fruit that tastes better and lasts longer. Research shows such a tomato to be only a few years away. USDA/ARS scientists (Horticultural Crops Quality Laboratory, 10300 Baltimore Ave., Beltsville, Md 20705) have genetically altered the levels of auxin, a hormone which causes a tomato to grow and ripen. It's the best-known and probably the most important of the five major plant hormones.

Scientists have been studying auxin for years. They've been able to change auxin levels, but the changes were expressed throughout the plant, not just in the fruit. The aim here is to control the hormone production so that it can be introduced into specific, targeted tissues, such as the fruit, without affecting the growth processes in other parts of the plant.

ARS scientists inserted an antisense copy of a specific gene from corn into a tomato to turn this gene off and lower auxin levels. Because the gene was put in with a fruit-specific promoter, only the tomato fruit was affected. The resulting fruit ripened more slowly.

Another plus for auxin: Decreasing the gene's level of expression throughout receptor plants caused them to easily form large numbers of roots from cuttings and spurred rapid root growth in germinating seedlings. This could be significant for plants that are difficult to root from cuttings and could increase the survival rate of seeds planted in dry soils.

Investigators expect this research to produce a store-bought tomato with vine-ripened taste in about three to five years. Field trials are next.

Further information. Jerry Cohen; phone: [phone]; fax: [phone]; email: [e-mail].