Research Projects

Population Genetics | Ecology and Epidemiology | Sustainable Agriculture

Population genetics

Late blight of potato and tomato

1. Molecular evolution of the Irish potato famine pathogen Phytophthora infestans

A grant was funded by National Geographic Society to collect herbarium samples infected with P. infestans from Farlow Herbarium, Harvard University, National Fungus Collection, USDA, Beltsville, and Royal Botanic Gardens, Kew England (Fig. 1). We optimized PCR procedures for amplification of DNA in dried lesions and amplified pathogen nuclear and mtDNA from historic specimens. Subsequent grants have been funded by the Plant Microbe Associations panel of the USDA - NRI to use mitochondrial DNA (mtDNA) and nuclear DNA gene sequences to unravel the genealogical history of the potato late blight pathogen. Objectives are to ask the following questions: 1) What ancestral strain was responsible for late blight epidemics that caused disease in 1845 in Ireland and Europe? Did the initial migrations of P. infestans into Europe, Ireland, and England in the 1840's contain one or multiple mtDNA types of P. infestans? 2) Does mtDNA and nuclear DNA gene sequence evidence justify the specific hypothesis that a common ancestor of P. infestans originated in South American population. We determined that the Ia mitochondrial haplotype was responsible for 19th century epidemics. An Andean origin for the pathogen has been documented.

Select papers

1. Trout, C.L., Ristaino, J.B., Madritch, M., and Wangsomboondee, T. 1997. Rapid Detection of Phytophthora infestans in late blight infected potato and tomatoes using PCR. Plant Disease 81:1042-1048.
2. Ristaino, J.B. 1998. The importance of archival and herbarium materials in understanding the role of oospores in late blight epidemics of the past. Phytopathology 88:1120-1130.
3. Fraser, D. E., Shoemaker, P. B., and Ristaino, J. B.  1999.   Characterization of isolates of  Phytophthora infestans from tomato and potato in North Carolina from 1993-1995.  Plant Dis. 83:633-638.
4. Groves, C.T. and Ristaino, J.B. 2000. Commercial fungicide formulations induce oospore formation and mating type change in P. infestans. Phytopathology 90:1201-1208.
5. Ristaino, J.B., Groves, C.T., and Parra, G. 2001. PCR Amplification of the Irish Potato Famine Pathogen from Historic Specimens. Nature 41:695-697.
6 . Wangsomboondee, T., Groves, C. T., Shoemaker, P. B., Cubeta, M. A., and Ristaino, J. B. 2002. Phytophthora infestans populations from tomato and potato in North Carolina differ in genetic diversity and structure. Phytopathology 92:1189-1195.
7. Wangsomboondee, T., and Ristaino, J. B. 2002. PCR detection of Phytophthora infestans in potato tubers. Plant Disease 86:247-253.
8. Ristaino, J. B. 2002. Tracking historic migrations of the Irish potato famine pathogen Phytophthora infestans. Microbes and Infection. 4:1369-1377.
9. May, K. J. and Ristaino, J. B. 2004. Identity of the mitochondrial DNA haplotype(s) in historic specimens from the Irish potato famine. 2004. Mycol. Res. 108:171-179. Supplemental tables.
10. Ristaino, J. B.  2006.  Tracking the evolutionary history of the potato blight pathogen with historical collections.  Outlooks in Pest Management 17:228-231.
11.Gomez-, L., Carbone, I., and Ristaino, J. B.  2007.  An Andean origin for Phytophthora infestans inferred from nuclear and mitochondrial DNA sequences.  Proc. Nat. Acad. Sci. 104:3306-3311.
12. Gomez, L. Forbes, G.  and Ristaino, J. B.  2007.  Phylogenetic relationships of a new species, Phytophthora andina, from the highlands of Ecuador that is closely related to the Irish Potato famine pathogen Phytophthora infestans. Mycologia submitted.

3. Phyophthora infestans mitochondrial DNA sequencing project
http://www.tigr.org/tdb/e2k1/pima1/index.shtml
1. Cruz Avila-Adame, Luis Gómez-Alpizar, Robin C. Buell, and Jean B. Ristaino. 2005. Mitochondrial genome sequencing of the haplotypes of the Irish Potato famine pathogen, Phytophthora infestans. Curr. Gen.49:39-46.

Bluemold of tobacco
1. PCR technology for the identification of the tobacco blue mold pathogen Peronospora tabacina and other pathogens that infect tobacco. A grant funded by the North Carolina Tobacco Foundation was used to collect inoculum of the tobacco blue mold pathogen from active epidemics in NC and the southeast and to develop a PCR based diagnostic assay for specific detection of Peronospora tabacina. Currently a real time PCR assay is being developed.

2. DNA fingerprinting to differentiate source inoculum of the tobacco bluemold pathogen. DNA fingerprinting to differentiate source inoculum of the tobacco blue mold pathogen - Grants have been funded by the North Carolina Tobacco Foundation and Commission to: 1) Collect isolates of the tobacco blue mold pathogen from active epidemics as they are reported by the Blue Mold forecasting system on flu-cured and burley tobacco in NC and regionally; 2) To maintain the collection on tobacco tissue culture and in cryogenic storage; 3) To use multigene gene genealogies to track migrations of the pathogen and identify sources of inoculum for epidemics in the state, regionally, and nationally.

Fig. 3. Peronospora tabacina causes the bluemold disease of tobacco. P. tabacina causes chlorotic lesions on the tobacco leaf

Fig. 4 . Bluish-gray sporangiospores of the blue mold pathogen Peronospora tabacina on the underside of a tobacco leaf.

Fig. 5. A systemic disease in plants can also occur. Brown necrosis of the stems and stunting can occur.

Website linkages

Bluemold forecasting website - http://www.ces.ncsu.edu/depts/pp/bluemold/
Bluemold APSNet feature -http://www.apsnet.org/online/feature/forecast/

Select papers

Ristaino, J. B., Johnson, M., Blanco-Meneses, M., Lui, B. and 2007.  Identification of the Tobacco blue mold pathogen, Peronospora tabacina by PCR.  Plant Dis. 91:685-691.