DR. Paul's Research Update
Mulch changes tomato gene activity

High-tech ag research pinpoints the advantages of more natural management strategies

By Paul Hepperly

September 10, 2004: Federal agricultural researchers Vinod Kumar and Autar Mattoo are experienced biotechnologists with extensive experience investigating how novel technologies might improve plant nutrition and production. As such, they represent an odd couple to pinpoint superior results stemming from more natural production systems. Nevertheless, the pair did just that, showing how a natural production system can increase favorable gene expressions in tomato compared to plastic mulched plants with synthetic fertilization.

Autar is a plant physiologist interested in plant aging. He and his co-workers at the USDA's Vegetable Laboratory in Beltsville found that vetch-mulched tomatoes of the variety Sunbeam were longer-lived and more productive in the field than same variety under standard production using black mulch and synthetic fertilizer. To find out why they got these unexpected results, the researchers went on to conduct a three-year field and laboratory study examining the gene product profiles from Sunbeam tomatoes under the two production systems.

Gene activity profiles showed that tomatoes from the more natural, vetch-mulched fields were higher in activity than those from plastic-mulched, synthetically-fertilized fields for at least 10 genes, including two defensive and two anti-aging genes.

The study also found that vetch-mulched tomatoes were able to resist fungal diseases more effectively and had delayed aging compared to their conventionally-grown counterparts. This USDA report, along with work at University of California--Davis on phenolic acid increases in plants grown in more naturalistic production systems, indicates that a subtle interplay of plant and environmental conditions are crucial to plant health and plant nutritive values.

Unfortunately, artificial systems are often accepted without extensive long-term testing or consideration of their potential side effects. The importance of this work is that it suggests a mechanism for the observed advantages of natural production methods compared to more artificial production systems.

Among the genes showing higher activity under more natural production methods were a chitinase gene, which produces an enzyme that eats up pathogenic fungal cell walls; osmotin, a gene regulating water flow into cells; and cytokinin receptor genes. Cytokinins are key plant hormones that are only produced by plant roots and serve to prevent premature leaf aging. They serve as a botanical 'fountain of youth' and help plants bud and grow optimally.

Thomas Sinclair of USDA-Gainesville has cautioned that studies of the complex nature of gene activity via gene product analysis are based on correlations and not on analyses of cause and effect. Nevertheless, results such as these underscore the wisdom of adopting precautionary positions with respect to drastic, uncontrolled changes in our food system.

For a good report on this work by Susan Milius, check out Science News Online for July 10, 2004.

Paul Reed Hepperly, Ph.D., is research and training manager at The Rodale Institute.