Rapid Detection of Red Rot Disease Pathogens (Pythium chondricola and P. porphyrae) in Pyropia yezoensis (Rhodophyta) with PCR-RFLP

Red rot disease is one of the best-known algal diseases infecting red algae Pyropia species. This disease decreases the quality and quantity of Pyropia aquaculture products in Korea, Japan, and China. Recently we found that Pythium chondricola (Oomycetes) infects blades of Pyropia yezoensis. Therefore, two Pythium species (P. chondricola and P. porphyrae) have been reported as red rot disease pathogens. In this study, we developed a species-specific molecular marker for distinguishing between the two red rot disease pathogens. Using a polymerase chain reaction restriction fragment length polymorphism method based on the mitochondrial cytochrome c oxidase subunit 2 (cox2) and nuclear ribosomal RNA large subunit regions, we classified these two Pythium species without a sequencing step. This new method had high specificity and efficiency for detecting red rot disease pathogens at the species level for both of the cultured and field samples. Therefore, the molecular markers developed in this study are effective for long-term monitoring of the infection and distribution pattern of each Pythium species in Pyropia aquaculture farms. Moreover, molecular monitoring can provide useful information for predicting infection and preventing mass mortality of Pyropia species by red rot disease.