Progress 10/01/05 to 09/30/06
Outputs
Progress Report 4d Progress report. This report serves to document research conducted under a reimbursable agreement between ARS and APHIS. Additional details of this research can be found in the report for the parent project, 1931-21000-011-00D, Genetic Improvement of Fruit Crops. Plum pox virus, one of the most serious threats to stone fruit production in the U.S., was detected in commercial stone fruit trees in PA, NY, and MI. It is not known if it can infect native species related to these commercial species. The objectives of the project are to evaluate the susceptibility and symptom expression of a wide range of Prunus species, native, naturalized, and ornamental, inoculated with plum pox virus strain D (Pennsylvania isolate). Information on the susceptibility of these species could be used for: 1) the formulation of PPV survey strategies of native, natural, and ornamental Prunus; 2) development of regulations for interstate movement or export of native,
naturalized, or ornamental Prunus; 3) future plantings of resistant ornamental Prunus should PPV become established in the U.S.; 4) use in planning interspecific crosses to develop resistance in commercial species should high levels of resistance or immunity be discovered. Of the 39 species or genotypes tested, 34 yielded at least one infected plant with an average of 37% of plants infected. Virus levels differed between genotypes suggesting variability in levels of susceptibility, but this could not be confirmed due to variability in infection dates, the number of inoculations and the survival and growth of inoculum buds. Presence of symptoms, immunoassay and other molecular analyses indicated that that 24 genotypes were moderately to highly susceptible. High levels of apparent resistance in seven species will be confirmed through additional testing.
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Progress 10/01/02 to 09/30/06
Outputs
Progress Report Objectives (from AD-416) The objective of this work is to evaluate the susceptibility and symptom expression of a wide range of Prunus species native, naturalized, and ornamental, inoculated with plum pox virus strain D, Pennsylvania isolate. Approach (from AD-416) Six plants of each of approximately 30 species tested will be inoculated by bud-grafting with budwood from trees infected with the Pennsylvania D strain of plum pox virus (PPV). One month following inoculation, trees will be exposed to an artificial 2-month cold dormancy period in a cold chamber. Following dormancy, inoculated trees will be moved to the greenhouse and symptoms of PPV will be evaluated as trees grow. ELISA and PCR will be used to critically evaluate infections symptoms; when apparent will be photographed. Significant Activities that Support Special Target Populations This report serves to document research conducted under a reimbursable agreement with USDA-APHIS. Additional details of research can be found in the report for the parent project 1931-21000-011-00D, Genetic Improvement of Fruit Crops, and in the publication included in the parent project report (Damsteegt, V. D., Scorza, R., Stone, A. L., Schneider, W. L., Webb, K., Demuth, M., and Gildow, F. E. Prunus host range of Plum pox virus (PPV) in the United States by aphid and graft inoculation. Plant Dis. 91:18-23). Plum pox (Sharka) is a serious virus disease of stone fruits caused by the Plum pox virus (PPV). Natural spread of the virus from tree to tree or orchard to orchard occurs by aphid transmission. Longer distance spread is mediated through grafting with infected budwood and movement of infected nursery stock. To determine which Prunus species could function as potential hosts and virus reservoirs, we used aphid transmission and grafting to evaluate the susceptibility of commercial, ornamental, and wild Prunus species to strains of PPV found in Pennsylvania. Following inoculation by aphids or grafting, test trees were observed for symptoms and analyzed by serological and molecular means (ELISA, PCR) through four cold-induced dormancy cycles over four years. Thirty-one of 33 Prunus species and cultivars tested were susceptible to infection by aphid transmission, and all 40 species and varieties became infected by grafting. In a few species, infection was very mild and only detectable by sensitive molecular assays (quantitative RT-PCR), while many species displayed clear symptoms, were highly infected, and maintained high virus levels throughout the four years of the study. These results indicate that a wide range of native and ornamental Prunus species are susceptible to U. S. isolates of PPV. Progress of the project was monitored through site visits that included joint work and research meetings. Phone and e-mail communication was also maintained.
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Progress 10/01/04 to 09/30/05
Outputs
4d Progress report. This report serves to document research conducted under a reimbursable agreement between ARS and APHIS. Additional details of this research can be found in the report for the parent project, 1931-21000-011-00D, Genetic Improvement of Fruit Crops. The objectives of the project are to evaluate the susceptibility and symptom expression of a wide range of Prunus species, native, naturalized, and ornamental, inoculated with plum pox virus strain D (Pennsylvania isolate). Information on the susceptibility of these species could be used for: 1) the formulation of PPV survey strategies of native, natural, and ornamental Prunus; 2) development of regulations for interstate movement or export of native, naturalized, or ornamental Prunus; 3) future plantings of resistant ornamental Prunus should PPV become established in the U.S.; 4) use in planning interspecific crosses to develop resistance in commercial species should high levels of resistance or
immunity be discovered. Of the 39 species or genotypes tested, 34 yielded at least one infected plant with an average of 37% of plants infected. Virus levels differed between genotypes suggesting variability in levels of susceptibility but this could not be confirmed due to variability in infection dates, the number of inoculations and the survival and growth of inoculum buds. Presence of symptoms, immunoassay and other molecular analyses indicated that that 24 genotypes were moderately to highly susceptible. High levels of apparent resistance in 7 species will be confirmed through additional testing.
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Progress 10/01/03 to 09/30/04
Outputs
4. What were the most significant accomplishments this past year? D. Progress Report: This report serves to document research conducted under a Reimbursable Ccooperative Agreement between ARS and the USDA, Animal Plant Health Inspection Service (APHIS). Additional details of research can be found in the report for the parent CRIS 1931-21000-011-00D, Genetic Improvement of Fruit Crops. The objectives of the project are to evaluate the susceptibility and symptom expression of a wide range of Prunus species, native, naturalized, and ornamental, inoculated with plum pox virus strain D (Pennsylvania isolate). Information on the susceptibility of these species could be used for: 1) the formulation of PPV survey strategies of native, natural, and ornamental Prunus; 2) development of regulations for interstate movement or export of native, naturalized, or ornamental Prunus; 3) future plantings of resistant ornamental Prunus should PPV become established in the U.S.; and
4) use in planning interspecific crosses to develop resistance in commercial species should high levels of resistance or immunity be discovered. Of the 39 species or genotypes tested, 34 yielded at least one infected plant with an average of 37% of plants infected. Virus levels differed between genotypes suggesting variability in levels of susceptibility but this could not be confirmed due to variability in infection dates, the number of inoculations and the survival and growth of inoculum buds. Presence of symptoms, high immunoassay (ELISA) absorbance values, or low real-time PCR CT values based on RNA sequence amplification indicated that that 24 genotypes were moderately to highly susceptible. High levels of apparent resistance in 7 species will be confirmed through additional testing.
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