Studies on signaling molecules and resistance factors involved in red rot disease causative agent, Pythium porphyrae (Oomycota) interaction with Porphyra yezoensis (Rhodophyta) and other marine algae.

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Screening of the cultivar and wild species of Porphyra sp.was performed by in vitro infection studies using the zoospores of Py.porphyrae to identify the red rot disease resistant species. The infection mechanisms involved in the host (Porphyra spp.) specific infection and disease initiation were understood by employing the epi-fluorescent and electron microscopy. The in vitro infection studies on Porphyra spp.and other marine algae had shown conclusively that the carbohydrates in the red algae were responsible for the zoospore encystment and attachmentTo understand the molecules involved in the host specific infection and disease initiation, cell walls of highly susceptible P.yezoensis and partially resistance P.tenuipedalis were isolated and their carbohydrate contents were analyzed for the encystment and formation of appressoria by the zoospores of the Py.porphyrae. From the in vitro carbohydrate analysis it was found that sulfated galactans present in the red algae were responsible … More for the host specific infection by the zoospores of Py.porphyrae.In vitro infection studies have identified the partially resistant non-cultivated species, P.tenuipedalis and P.subrbiculata to Pythium porphyrae. To obtain disease resistance cultivar strains, somatic hybridization was performed between the highly susceptible P.yezoensis (cultivar variety) and P.tenuipedalis (non cultivar sp.) and produced nine hybrid varieties of which two hybrids were found to be partially resistance towards Py.porphyrae.In vitro infection tests have shown the presence of resistant factors for red rot disease in P.tenuipedalis which must be interfering with the signaling mechanism of host specifie infection by Py.porphyrae. As the understanding of signaling mechanism helps in the development of red rot disease resistant varieties, monoclonal antibodies were developed as probes with the view of identifying the receptor molecules on the zoospore surface that are responsible for host specific infection. And these antibodies were shown to be as diagnostic tools for the early disease detection to take appropriate disease control measures. Less