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Identification and functional characterization of nematode parasitism genes

feeding structure
The multinucleate feeding structure - syncytium induced by G. rostochiensis within a host root

G. rostochiensis is a sedentary endoparasitic nematode that has evolved an intimate parasitic relationship within host plant roots by transforming selected root cells into elaborate feeding structures that provide the nutrients required for the development and reproduction of the nematode. Parasitism genes are expressed in the esophageal gland cells of the parasite and encode secretory proteins that represent major signaling molecules involved in nematode infection and parasitism of host plants. We use biochemical, molecular, genomic, and proteomic tools to characterize the function of nematode parasitism genes. Our study of a chorismate mutase encoding gene has led to the discovery of the first example of alternative splicing in plant parasitic nematodes and revealed an important mechanism of alternative splicing for regulating chorismate mutase activity during nematode parasitism. Another area of study focuses on genes encoding a novel class of CLV3/ESR (CLE)-like peptides. Recent evidence suggests that cyst nematodes secret ligand mimics of plant CLE peptides to modify selected root cells into multinucleate feeding structures. We use a variety of approaches to understand the mechanism of ligand mimicry in plant parasitism by cyst nematodes.

Development and releasing of nematode resistant potato varieties
The use of nematode resistant cultivars is the most economical and environmentally-safe means of nematode control. We have a longstanding collaboration with the Cornell Potato Breeding Program (Dr. Walter De Jong at Plant Breeding and Genetics) and faculty at the Department of Horticulture (Dr. Don Halseth) and the Department of Plant Pathology and Plant-Microbe Biology (Dr. Keith Perry) to develop and release G. rostochiensis resistant potato varieties. We also screen potato clones and varieties developed by many other breeding programs. Recently plant-mediated RNAi targeting nematode parasitism genes has revealed its potential for generating novel nematode resistant plants. We are evaluating the utility of this RNAi-based technology for broad resistance in potato against Globodera pests.

Providing scientific and technical support to the USDA-APHIS and NYS nematode quarantine programs
Both species of the potato cyst nematode, G. rostochienis and G. pallida, are quarantine pests of national importance. In the U.S., G. rostochiensis has been confined to nine counties in the state of New York. Current control of G. rostochiensis relies on strict regulatory and quarantine procedures and the use of resistant potato varieties to prevent its further spread from the state of New York. However, a new pathotype, Ro2, has become established that is virulent on potato cultivars resistant to the endemic pathotype, Ro1. To date, there are no commercially-available potato cultivars resistant to Ro2, emphasizing an urgent need of developing Ro2 resistant potato varieties. The USDA-APHIS conducts annual golden nematode soil surveys in the state of New York. Suspected cysts recovered from the surveys will be examined by our program to determine the viability and pathotype of the nematode.

The discovery of these potato pests is always associated with quarantine and trade embargoes. However, potato cyst nematodes continue to spread in North America. Recently, G. rostochiensis was detected for the first time in Quebec and two potato seed producing fields of Alberta, Canada. In addition, G. pallida, not previously detected in the U.S., was recently identified in multiple potato fields in the state of Idaho. G. pallida is more difficult to control than G. rostochiensis because of its higher degree of genetic variability and the lack of potato cultivars with full resistance. We are involved in a multi-institutional project to provide technical assistance to the eradication of G. pallida in Idaho.

cysts on potato roots

Gold and brown colored G. rostochiensis cysts on potato roots

visual exam

Examination of G. rostochiensis cysts on roots of potato clones developed by potato breeding programs