Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/1/2008
Publication Date: 6/1/2008
Citation: Montero-Astua, M., Vasquez, V., Turechek, W., Merz, U., Rivera, C. 2008. Incidence, distribution and association of Spongospora subterranea and Potato mop-top virus in Costa Rica. Plant Disease. 92:1171-1176. Interpretive Summary: Powdery scab of potato and Potato mop-top virus (PMTV) are serious threats to potato production throughout the world, and are recognized as emerging diseases in North and Latin America where they were recently detected in Costa Rica. The powdery scab fungus is a known vector of PMTV. A survey was conducted in 39 potato fields in Costa Rica to determine the incidence and association of powdery scab and PMTV in fields located in Costa Rica’s two major potato production regions. The incidence of both diseases ranged from 0 to 100% within individual fields, with incidences lower than 40% occurring in more than 70% of the fields. A significant but low degree of association was found, indicating that the powdery scab fungus transmits PMTV in Costa Rica in low frequency. These results suggest that seed transmission of PMTV, as opposed to vector transmission from infested soils, is an important component of pathogen transmission; therefore, producers should be more diligent in potato seed certification to reduce PMTV epidemics in Costa Rica.
Technical Abstract: A survey was conducted in 39 potato (Solanum tuberosum L.) fields in Costa Rica to determine incidence and association of Spongospora subterranea f. sp. subterranea and Potato mop-top pomovirus (PMTV). The fields were located in Costa Rica’s two major potato production regions, and were further characterized by their altitude. Six hundred thirty-three paired samples of leaf tissue and corresponding tubers were collected, assessed visually for disease, and subsequently assayed by ELISA. Moreover, soil samples were collected at ten of the fields surveyed and were evaluated for both pathogens via ELISA and bioassay. The incidence of both diseases ranged from 0 to 100% within individual fields, with incidences lower than 40% occurring in more than 70% of the fields. Higher incidences were found in fields located at higher altitudes. Of the 633 paired samples, 179 and 146 were positive for PMTV and S. subterranea, respectively, according to ELISA in either the foliage or tubers. A low correlation was found for PMTV visual symptoms and ELISA test results. Only 14 of the 81 foliar samples testing positive for PMTV had visual symptoms; the remaining 67 samples were asymptomatic. Conversely, comparison of visual evaluation with detection of S. subterranea by ELISA on tubers showed that 70% of the results were coincident and indicated a moderate degree of association. S. subterranea was detected in four of ten soil samples tested by DAS-ELISA. Soil-borne PMTV was detected by TAS-ELISA in roots of bait plants sown in these soil samples. Co-occurrence of both pathogens was detected in 64 samples. A significant but low degree association for vector and virus was determined and data suggests that S. subterranea is participating in the transmission of PMTV in Costa Rica in low frequency.