The soybean cyst nematode (SCN), is a highly specialized sedentary endoparasite of soybean roots that causes substantial losses to soybean producers worldwide. The predominant management strategies include planting resistant soybean cultivars and rotating with non host crops.

Host resistance, however, is the most environmentally and economically sound approach. It continues to be the number one method utilized by soybean producers for managing this nematode.

More than 100 sources of SCN resistant soybean germplasm have been identified. However, only a few have been incorporated into soybean breeding programs. Currently, SCN field populations are classified as HG-types based upon their ability to reproduce on the present sources of resistance in soybean.

Because SCN reproduces sexually, HG-types actually represent mixtures of individual genotypes that may vary in virulence. Planting soybeans with resistance derived from a narrow genetic base with existing heterogeneous field populations of SCN means that we are slowly reducing our ability and options for managing this devastating soybean pest below threshold levels.

Project Objectives

This project will provide a better understanding of how SCN resistance genes function to induce plant defense and how this process is modulated by SCN proteins. This will enable the researchers to develop methods to increase the longevity of current natural sources of resistance to SCN and/or develop novel types of SCN resistance using biotechnological approaches to combat genetically variable field populations of SCN. Three specific objectives:

1. Identify nematode gene products that ineract with SCN R gene products using proteomic-based strategies.
2. Identify components of the downstream signaling pathway for resistance to SCN.
3. Use TILLING to identify alternative alleles for resistance to SCN and test the functionality of signaling pathway candidate genes.

This project will take advantage of developed high-throughput reverse genetic and proteomic tools to advance knowledge of SCN interaction. From the time SCN penetrates and migrates within soybean roots, to the time it establishes a feeding site, it induces several changes in cellular metabolism and gene expression.

Candidate SCN resistance genes, soybean genes expressed in response to nematode infection, and SCN parasitism genes have been isolated. However, the underlying molecular mechanism(s) of the interaction between soy bean and SCN is imperfectly understood.

Plant and nematode genomics projects have identified a large number of genes for which a function has yet to be assigned. To study the functional aspects of these genes, proteomic-based strategies and reverse genetic approaches can be employed. To decipher the resistance mechanisms involved in the interaction between soybean and SCN at the molecular level, the researchers will use an integrated set of technologies that combine the yeast two-hybrid system with screening of a large collection of ethylmethanesulfonate (EMS) mutants of the SCN resistant soybean cultivar Forrest using TILLING (Targeting Induced Local Lesions in Genomes).

Impact

This collaborative, innovative, discovery research will seek to define the underlying mechanism of soybean resistance to SCN, the product of which has both economic and environmental potential.

Implementation of a high-throughput screen will accelerate the functional analysis of SCN resistance genes and identify plant and nematode products that mediate the upstream and downstream resistance gene signaling pathways.

Ultimately, the information gained from this research could lead to the development of soybean with novel and/or more durable resistance to SCN to produce marketable products that will benefit soybean producers worldwide, thereby enhancing the profitability of American agriculture.