Submitted to: American Journal of Potato Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: August 4, 2006
Publication Date: December 1, 2006
Citation: Deahl, K.L., Jones, R.W., Perez, F.G., Shaw, D.S., Cooke, L.R. 2006. Characterization of isolates of phytophthora infestans from four solanaceous hosts growing in association with late-blighted potatoes. American Journal of Potato Research. 41:1635-1639. Interpretive Summary: Although late blight is a highly significant, well-studied disease of potato, very little is known about this disease caused by the same organism on other related plants. Isolates of the late blight pathogen, collected from potatoes and weed hosts, in four USA locations and one UK location, were evaluated with several molecular markers for disease source determination and strain relatedness. This paper reports the results of strain characterizations which reveal that host-range extension may be one of the mechanisms involved in pathogenic changes in natural populations of the pathogen in various locations. Monitoring of pathogen populations in alternate or bridging hosts, found growing within or near potato crops, is important, since these may play a major role in the introduction and spread of damaging pathogens to new locations. This information will be used by farmers, agricultural agents and scientists in an attempt to control late blight.
Technical Abstract: The oomycete, Phytophthora infestans, is a devastating pathogen of potato worldwide. Several strains of P.infestans are able to infect other cultivated and weed species of the family Solanaceae and cause symptoms similar to late bli ght on these hosts. Changes in P.infestans populations have stimulated investigations to determine if potato strains from more recent immigrant populations are able to infect a wider host-range than those from the older population. Host-range extension may be one of the mechanisms involved in pathogenic changes in natural populations of P.infestans in various locations. Isolates of P. infestans, collected from potatoes in four USA locations and one UK location, were evaluated for mitochondrial DNA (mtDNA) haplotype, as well as mating type, metalaxyl insensitivity, allozymes of glucose-6-phosphate isomerase and peptidase, and DNA fingerprint with the RG57 probe. This paper reports characterizations of P.infestans isolates from four Solanaceous hosts growing within and around fields of blighted potatoes. Analysis confirmed the close similarity of the petunia, hairy nightshade and black nightshade isolates with potato isolates. However, tomato and potato strains had distinctly different fingerprints which indicates another disease source. Potato growers should be aware that both weed and cultivated Solanaceous species can be infected with P.infestans and may serve as clandestine reservoirs of inoculum. Because some of these plants do not show conspicuous symptoms, they may escape detection and fail to be either removed or treated. Monitoring of pathogen populations in bridging hosts is important, since these may play a major role in the introduction and spread of damaging pathogens to new locations.