Phytonutrients and Genomics of Organic Tomatoes: Soil Fertility and/or Plant Defense

In previous studies, we showed that apples, strawberries, and tomatoes grown with organic nitrogen fertilizer sources had higher phytochemical contents than those fertilized with readily available sources of nitrogen. It is also possible that increased pest herbivory in the field stimulates plant defenses that elevate these phytochemicals in organic crops. To test the relative contributions of soil fertility management and herbivory to phytochemical accumulation we conducted a greenhouse study of tomato plants grown in exclusion cages and either fertilized with organic or readily available nitrogen sources, and exposed or not to herbivory by aphids. We have harvested the fruit and vegetative tissues of these plants, and are in the process of measuring the phytochemical concentrations/contents of a range of fruit sizes. The most significant findings to date are that the yields of green immature fruit and total vine weights were slightly greater for the conventionally fertilized tomato plants than for the organic fertilized. Nevertheless, these findings in favor of the conventional treatment are overshadowed by the higher fruit soluble solids (sugars) content and reduced aphid infestation of the organically fertilized plants. We will also measure gene expression in leaves and fruit of selected samples. These experiments will enable us to determine relative contributions of soil carbon/nitrogen and herbivory to phytonutrient accumulation in fruit and how differential gene activity may guide these two mechanisms in organic cropping systems. This project supports the 2010 BIOAg priority that sustainable farming practices increase food quality and nutrition.

Grant Information

  • Project ID: 088
  • Project Status: Complete





Additional Funds Leveraged

No additional funding has been applied for yet. Several USDA competitive grant programs would be applicable for future funding of this research, including the National Institute of Food and Agriculture’s (NIFA) Organic Research and Extension Initiative (OREI), Specialty Crop Research Initiative (SCRI), or the Agriculture and Food Research Initiative (AFRI) Foundational Grant Program. It may be helpful to initially apply for a planning grant in order to facilitate effective project planning and development.


Short-Term: The tomato greenhouse experiment and all growth, yield, mineral, phytochemical, and gene sequencing analyses are completed. Statistical and genomic mapping analysis of data is complete. Additional analysis of the genomic data is expected to reveal the actual pathways and genes that are impacted by the two soil management regimes. We are seeking additional funding to complete the work. Following this we will prepare and submit a manuscript for publication, which should lead to a federal grant application.

Intermediate-Term: We expect that the knowledge gained from this and subsequent projects on the phytochemical and genomic patterns of horticultural crops grown under organic or conventional fertility management will permit us to determine the genetic basis for plant defense mechanisms and improved nutritional quality for human consumption. It will also inform the development of more effective farming methods in order to produce more phytonutrient dense crops.

Long-Term: Gaining the stated intermediate-term knowledge will allow us develop more effective farming methods and targeted genes for crop breeding in order to enhance agricultural sustainability and improve nutritional quality of horticultural food crops for public health.