Submitted to: Canadian Journal of Plant Pathology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 10/5/2007
Publication Date: 9/1/2008
Citation: Sun, W.X., Jia, Y.J., Wu, Y.M., Zhang, X.G., Oneill, N.R. 2008. Genetic Diversity in Phytophthora capsici from Eastern China. Canadian Journal of Plant Pathology. 30(3):414-424. Interpretive Summary: Phytophthora blight caused by the fungus Phytophthora capsici is a common, serious disease of numerous crops in the U.S. and many other parts of the world. The disease is one of the most serious threats to processing peppers, causing up to 100% yield losses in China. Recent surveys show that the aggressiveness of strains of the fungus as well as the morphology of strains vary considerably, and that some strains do not attack at all. We conducted molecular studies that determined the diversity in populations of these fungi, their relationship to other species of fungi, characteristics of strains that are pathogens, and additional relationships among strains. Molecular patterns in Chinese isolates were similar to those from the U.S. and Japan. The information could lead to the rapid detection of the specific type of fungus present. This research will be useful to breeders, seed companies, APHIS, and research scientists concerned with controlling diseases caused by strains of this fungus.
Technical Abstract: Assessment of variability of Phytophthora capsici was based on virulence tests of 37 isolates and on random amplified polymorphic DNA (RAPD) analysis of 37 isolates from China. In addition, 17 isolates of P. capsici from other countries were assessed in the virulence and RAPD analyses. Five isolates of P. parasitica and two of P. infestans were also included in the RAPD analysis. Virulence tests showed that certain isolates were virulent only on specific plants. China isolates of P. capsici were grouped into 9 pathotypes using 9 pepper cultivars differentials. These groupings also encompassed 17 isolates from other countries. RAPD analysis of all 61 isolates using 12 primers produced 129 fragments, of which 97.2% were polymorphic. Similarities among P. capsici isolates from China ranged from 35 to 100%. In the RAPD dendrogram, one of five P. capsici isolates from Korea, and another one of seven from France clustered within a major group with China isolates. There was a strong association between RAPD and pathotype groups. P. capsici was 36% similar to P. infestans and only 20% similar to P. parasitica. The levels of DNA variability and virulence among isolates showed that the population of P. capsici in China has highly diverse, and neither genotype nor pathotype of the population of P. capsici isolates were consistent with their geographic origins and collection time.