Grant Information
| Knowledge Area | Subject of Investigation | Field of Science | Percent |
|---|---|---|---|
| 212 - Pathogens and Nematodes Affecting Plants | 1310 - Potato | 1101 - Virology | 85% |
| 212 - Pathogens and Nematodes Affecting Plants | 1599 - Grain crops, general/other (includes buckwheat, millet, triticale) | 1120 - Nematology | 15% |
Viruses and cyst nematodes present the United States potato industry with its most severe regula-tory problems. This project primarily focuses on potato cyst nematodes (PCN), Potato virus Y (PVY), and Luteoviruses including Potato leafroll virus (PLRV) and the viruses causing barley yellow dwarf disease of cereal crops. The two species of PCN (Globodera rostochiensis and G. pallida) are quaran-tine pests that cause direct crop losses, increase pest control costs, constrain cropping patterns, de-value property, and interfere with domestic and international trade of potato and many other soil-associated crops. PVY and PLRV cause crop losses, interfere with marketing and trade of potato, and are the major diseases targeted by seed potato certification programs. Additionally, management options for vector-borne viruses are extremely limited and an understanding of the mechanisms by which viruses are carried between hosts by insects will lead to new targets of opportunity to control these pathogens. In recent years, PCN and the necrotic strains of PVY have been spreading to new areas. It has been determined that the population genetics of PCN and viral pathogens are far more dynamic than previously thought, and these genetic shifts profoundly influence disease detection and management strategies. The overarching research goal is to develop an understanding of the major genetic and environmental factors that drive the dynamics of nematode and virus diseases. Multifaceted objectives needed to accomplish this research goal include: the improvement of detection and management strategies of the various pathogen populations, the identification of genetic mechanisms that regulate nematode and virus pathogenicity and pathogen movement within the crops, and the development of new sources of resistance in potato germplasm. Approaches include epidemiological and etiological studies to identify major factors contributing to the spread and diversification of these pathogens, fundamental studies of the mechanisms of pathogenesis and transmission of PCN and viruses, respectively and the collaborative development of potato germplasm with effective resistance to PCN and viruses. Rapid identification and containment, coupled with new strategies for management of nematode and virus diseases will help the U.S. potato industry remain viable and allow them to expand market share.
Development of management options for emerging pathotypes of potato cyst nematode (G. rostochiensis). The discovery of a new race of golden nematode (G. rostochiensis Ro2) has adversely impacted the New York potato industry and the successfulness of the nematode quarantine program implemented in New York state due to the fact that there is not a single commercially-acceptable potato variety with resistance to Ro2. We developed a four-year management plan that utilizes NY140, an advanced breeding clone, as a major resistant source for Ro2 control. The plan was extremely effective in suppressing Ro2 infestations in the field and has been approved by USDA-APHIS and the New York State Department of Agriculture & Markets for implementing into the nematode quarantine program. This not only helps protect the integrity of nematode quarantine in New York, but offers a solution for potato growers to profit from their Ro2-infested land. Reduction of Potato Virus Y (PVY) incidence in seed stocks and the potato crop. Research identified the scope and specifics of the PVY problem in U. S. seed potato production. Continued surveys of PVY populations from around the U.S. documented continued strain shifts and the emergence of new strain variants. This led to the development of new diagnostic assays that can better detect and differentiate the PVY strains. Discoveries of the emerging and changing PVY strains also modified seed potato certification programs. Discoveries connected with this objective generated nearly $11 million in grants to study the genetics and management of PVY in potato. Discovery of candidate nematode parasitism genes and their associated host proteins contributing to plant parasitism. Plant-parasitic nematodes including potato cyst nematodes (PCN) secrete effector proteins originated from their esophageal gland cells to promote successful infection. We have cloned a diverse group of effector genes from PCN and demonstrated that many play a critical role in nematode parasitism and virulence. The functional form of one group of nematode-secreted effectors is a 12-amino acid glycosylated peptide sharing striking structural similarity with plant peptides. This provided direct evidence that nematode effectors are ligand mimics of plant hormones that regulate plant growth and development. The significance of this work was demonstrated by a National Science Foundation grant, several high-impact journal publications, as well as a patent and a patent application. Studies on another effector family revealed they have a critical role in suppressing plant innate immunity, adding new evidence to support a function of nematode-secreted effectors in interfering with host immunity to promote infection. Further research demonstrated that plant-derived RNAi silencing of nematode effector genes and interfering with host receptors that recognize effectors are effective methods for generating engineered nematode resistance in crop plants. This achievement has been demonstrated by two patents and one patent application. In addition, our study on effectors has led to the development of plant immunity assays that are optimized for the plant-nematode pathosystem as well as molecular diagnostic methods for identifying different PCN species, a technology that is patented and can be implemented into nematode quarantine programs to monitor the potential spread of PCN in the U.S. Understanding circulative virus transmission competence in aphid populations. Proteomic approaches coupling co-immunoprecipitation with mass spectrometry have identified aphid, aphid symbiont, and plant proteins that interact with specific protein domains on the surface of the virus capsid. Several of the aphid and symbiont proteins were useful as protein biomarkers to rapidly identify aphid populations that are efficient vectors of viruses. Forms of Cyclophilin were found in aphids that differed in their ability to transmit viruses. Cyclophilin functions to guide the folding and transport of other proteins. In collaboration with scientists at the University of Washington and the Volcani Center in Israel, Cyclophilin was found to be associated with the ability of whiteflies to transmit viruses. The Cathepsin B protein was discovered to regulate the transmission of viruses by aphids as it is an aphid digestive enzyme and when expressed at higher levels it impaired virus transmission. These were the first studies to identify the functionality of aphid proteins in regulating virus transmission. Determined the resistance of potato cultivars and clones to pathotypes of PCN (G. rostochiensis). Using host resistance is the most effective and sustainable means for nematode control. During this 5-year plan cycle, we screened more than 2,080 and 460 clones for resistance to the Ro1 and Ro2 pathotypes of potato cyst nematode. While the majority of these potato clones were from the Cornell University potato breeding program, the recent detections of G. rostochiensis in Canada and G. pallida in Idaho, many potato breeding programs in the country sent clones for evaluation. Our collaborative efforts have led to the release of a new G. rostochiensis resistant varieties �Huckleberry gold� (USDA-ARS Aberdeen, Idaho) and �Waneta� and �Lamoka� (Cornell University), as well as the identification of a list of existing US varieties with resistance to G. rostochiensis Ro1. As the only research program in the U.S. authorized to work on G. rostochiensis, our collaborative efforts on developing and releasing PCN resistant potato varieties have played a central role in ensuring that G. rostochiensis does not spread further within New York state or to any other states. Waneta and Lamoka are widely planted in the U.S. and their widespread adoption has two important consequences for nationwide, long-term control of G. rostochiensis; wherever they are grown, G. rostochiensis Ro1 cannot multiply and spread, secondly, both cultivars are used as parents in many breeding programs because they have excellent processing quality. This will also spread the G. rostochiensis resistance gene to other new cultivars. Furthermore, our multiyear tests both in the greenhouse and the field confirmed that the advanced clone �NY140� is resistant to Ro2 and was extremely effective in reducing Ro2 infestations in the field. NY140 may be released as a named variety in the near future. Determine the susceptibility of potato cultivars to potato tuber necrotic ringspot disease (PTNRD) caused by some necrotic strains of Potato Virus Y (PVY). PVY is the number one disease affecting seed potato production in the U.S. and is responsible for millions of dollars in annual crop loss, farm income and domestic and international trade. There are no effective PVY management strategies. Host resistance would be the best means of control, but resistance is not available in the widely grown and consumer accepted potato varieties. In collaboration with other ARS and University of Idaho researchers, two different approaches were developed to better understand virus resistance; the use of small RNAs (sRNAs) to suppress virus replication and the characterization of partial resistance genes collectively known as Ny genes. Transgenic potatoes expressing a PVY protein coat-protein derived inverted hairpin RNA (ihRNA) exhibited resistance to multiple PVY strains in glass house and field studies. Deep sequencing of the small RNA population of transgenic plants indicated high levels of siRNA production from the transgenic hairpin construct. Efficient hairpin formation and processing for the production of siRNAs conferred resistance to infection by PVY in transgenic potato plants. The poorly characterized Ny genes manifest a type of resistance to PVY that causes plant cell death when the plant cells become infected. This type of resistance ultimately kills the infected plant, but it does prevent further spread of the virus and ultimately reduces the number of plants infected by PVY. We identified a number of U.S. potato cultivars possessing this resistance and studied its effectiveness against multiple PVY strains. The resistance genes were effective at slowing the spread of the older strains of PVY, but they were not effective against strains of PVY emerging in the U.S. These varieties are likely contributing to the rapid rise of virus strains not affected by the resistance genes.