A MOLECULAR BASIS FOR DELAYED FOLIAR SENESCENCE AND TOLERANCE TO FOLIAR DISEASES IN TOMATO PLANTS CULTIVATED IN A HAIRY VETCH BASED ALTERNATIVE AGRICULTURE SYSTEM

Authors: KUMAR, VINOD - USDA,ARS, VEG LAB; MILLS, DOUGLAS - -FORMERLY USDA; Anderson, James; Mattoo, Autar

Submitted to: Science Magazine
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/7/2003
Publication Date: 4/7/2003
Citation: Kumar, V., Mills, D.J., Anderson, J.D., and Mattoo, A.K. 2004. An alternative agriculture system is defined by a distinct expression profile of select gene transcripts and proteins. Proc. Natl. Acad. Sci. USA. 101:10535-10540.

Interpretive Summary: Conventional agriculture has continued to heavily rely on chemicals ' fertilizer and pesticides, particularly for fruits and vegetables, as a means of preserving yield and quality. However, such an excessive chemical input to maximize yields has, generally, not favored the ecosystem. Concerns about the environment and ecosystem have catalyzed efforts to seek alternative agricultural practices. The need is for conservation and preservation of the soil, suppression of weeds, pathogens and pests, and yield maintenance/improvement, using practices that allow for long-term sustainability of agriculture. In very high chemical input systems, such as fresh market tomato production, the use of legume (Vicia villosa Roth.; hairy vetch) cover crops offers advantages as a biological alternative to commercial fertilizer and in promoting longevity and lesser incidence of foliar diseases. Despite publications that spell out advantages of alternative farming practices, a successful transition from conventional to alternative has not generally occurred. Alternative agriculture practices are still perceived to be in their infancy where science is concerned. It is, therefore, imperative that the molecular biology behind the beneficial aspects of legume cover crop be explored and revealed, because it can provide the scientific legitimacy for adopting alternative farming practices. As a step toward that goal, we sought specific up- or down-regulated gene transcripts and proteins coincident with reduced defoliation and increased disease tolerance in hairy vetch grown tomatoes. We demonstrate here that hairy vetch grown tomatoes are defined by a fundamentally distinct expression profile of gene transcripts and proteins that may be related to differential hormone(s) signaling. This information will be of use to agriculturists, molecular biologists and plant physiologists interested in developing sustainable agriculture systems.

Technical Abstract: Conventional agriculture has relied heavily on chemical inputs that have negatively impacted the environment and increased production costs. Transition to agricultural sustainability is a major challenge because alternative agricultural practices need to be analyzed in a molecular biological sense to provide a sufficiently informative knowledge base from which to determine adoption of alternative farming practices. We show a molecular basis for delayed foliar senescence and tolerance to foliar diseases in tomato plants cultivated in a legume (hairy vetch) mulch-based alternative agricultural system. In the hairy vetch-cultivated plants, expression of specific and select classes of genes is up regulated compared to those grown on black polyethylene. These include: N-responsive genes such as NiR, GS1, rbcl, rbcS, and G6PD; chaperone genes such as hsp70 and BiP; defense genes such as chitinase and osmotin; a cytokinin-responsive gene CKR; and GA20 oxidase. We present a model about how their protein products likely complement one another and effect efficient utilization and mobilization of N, promote defense against disease and enhance longevity.