|Abdul Baki, Aref|
Submitted to: Journal of Experimental Botany
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/12/2008
Publication Date: 5/9/2008
Citation: Neelam, A., Cassol, T., Mehta, R.A., Abdul Baki, A.A., Sobolev, A., Goyal, R.K., Abbott, J.A., Segre, A.L., Handa, A.K., Mattoo, A.K. 2008. A field-grown transgenic tomato line expressing polyamines reveals legume cover crop mulch-specific pertubations in fruit phenotype at the levels of metabolite profiles, gene expression and agronomic characteristics. Journal of Experimental Botany. 59:2337-2346. Interpretive Summary: Achieving agricultural sustainability in an eco-friendly and economic manner to meet the demands of a growing world population is a great concern to agriculture scientists. The estimate is that over the next 20 years agricultural production needs to double from the same acreage of land. Heavy chemical inputs in conventional agriculture have negatively impacted the ecosystem while current agricultural production has stagnated. The need of the time is for optimizing alternative strategies that achieve production/quality yields as well as reduce chemical inputs (fertilizer, pesticides, fungicides and herbicides), soil erosion, chemicals/nutrient leaching, and weeds. From consideration of environmental issues, no-till agriculture seems superior over conventional and organic agriculture. So too is the potential in adopting genetic modification. Different integrative systems including legume-based alternating cropping systems have been shown to produce higher yields while reducing carbon and nitrogen losses in diverse crops. Our studies on a vegetable crop presented here demonstrate compatibility between, and integration of, on-farm produced organic inputs and field production of genetically engineered, value-added crops such as tomatoes. Integrating genetically modified crops with sustainable agricultural practices would mitigate the impact of intensive practices on the environment and simultaneously address the issues of crop productivity, protection and quality. Our study suggests a new paradigm for sustainable agriculture that decreases the disadvantages of conventional agriculture and increases environmental congeniality and economic viability of future agriculture. It shifts the current paradigm toward sustaining future food production and addresses the opportunity of a ‘second paradigm’ that relies on new germplasm adaptable to adverse soil conditions, enhanced soil biological activity, and efficient use of nutrient cycling with minimal external inputs. These data are important to agriculturists and plant biologists interested in finding alternatives to chemicals for increasing quality and production of crops.
Technical Abstract: Emerging environmental issues including chemical pollution of soil and water due to heavy use of chemicals in conventional agriculture together with concerns about meeting the food needs of the world’s growing population have necessitated a paradigm shift toward sustainable alternatives to conventional agriculture. Toward that goal, we have assessed the compatibility of genetically engineered tomato genotypes carrying novel and value-added traits with sustainable production systems that utilize reduced-till, N-fixing and non-N fixing cover crops. Such an integrative model holds the promise of value addition to crops, benefit to the environment by decreasing fertilizer and pesticide use, preserving agricultural land as well as reducing economic burden on the farmer. Five transgenic tomato genotypes (anti-sense tomato ACC synthase-2, cosuppressed tomato fruit lipoxygenase and fruit-specifically expressed yeast S-adenosylmethionine decarboxylase (ySAMdc) and their hybrids), together with a control non-transgenic line, were grown in N-fixing leguminous hairy vetch (Vicia villosa Roth) (HV) mulch, non-leguminous rye mulch and conventional black polyethylene (BP) mulch. Transgenic lines fared equally well both in HV and rye compared to BP. Fruit set, size and yield of HV and rye grown transgenic plants were equivalent to or higher than those grown on BP except for one hybrid transgenic line. Genotype (G) X mulch-dependent (E) interactions affecting plant phenotype and fruit characteristics were revealed and exemplified by NMR spectroscopic profiles of twenty fruit metabolites, and expression patterns of the ySAMdc transgene and tomato SAMdc and E8 genes in fruits, between a non-transgenic and transgenic (579HO) line accumulating higher polyamines, spermidine and spermine. Significantly higher accumulation of asparagine, glutamate, glutamine, choline and citrate concomitant with a decrease in glucose was observed in the non-transgenic fruits during later stages of ripening when grown on HV compared to BP. Phenyalanine accumulated in the 556AZ control red fruit grown on HV but is significantly lower in the transgenic red fruit from HV-grown line 579HO. Further, this study demonstrates that HV mulch enables a metabolic system in tomatoes akin to the one in higher polyamines-accumulating transgenic fruit that have higher phytonutrient content.