Submitted to: HortScience
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/19/2010
Publication Date: 8/1/2010
Citation: Schultz, D., Donahoo, R., Tejeda, S., Perez, F.G., Deahl, K.L. 2010. A survey of Tomato and Potato fields in Florida reveals unique genotypes of Phytophthora infestans between 2005 and 2007. HortScience. 45:1064-1068. Interpretive Summary: Although it has been more than 160 years since the Irish Potato Famine, most domesticated potato and tomato varieties in the U.S. still lack the innate ability to ward off the pathogen that caused that dramatic event. Scientists have discovered that one of the reasons for this lack of resistance is due to the rapid rate of evolution or migration of pathogenic strains of the pathogen. This manuscript describes the chacterization of new strains of the pathogen that caused huge crop losses in south Florida for three years and contributed to the blight epidemic experienced on the U.S. east coast in 2009. Therefore, it is important for the farmer and the consumer to continuously monitor the population shift of this pathogen in efforts to develop an effective integrated management strategy for disease control.
Technical Abstract: Late blight, caused by Phytophthora infestans, affects tomatoes and potatoes in Florida during the winter-spring crop season. During the 2005 season, late blight epidemics were severe and chemical control was largely ineffective. Isolates from 2005 2007 were characterized based on growth on three media, phenotypically based on mating type, pathogenicity, and sensitivity to metalaxyl and genotypically based on two isozymes, mitochondrial DNA (mtDNA), and genomic profiling using the RG57 probe. Isolates collected in this survey were all A2, mtDNA Ia, and homozygous 100 at the Pep locus. Novel genotypes infecting tomato were observed based on the Gpi locus and RG57 genomic profile. We propose US-20 for the collection of clonal isolates recovered during the 2005 season, and US-21 for clones recovered during 2006 and 2007. In addition to these novel genotypes recovered from tomato, an isolate recovered from potato was found similar to US-14, yet varied at one locus. The findings of the survey in south Florida and their implications are presented.