| China has become the largest potato producer in the world since 1993, and shared more and more portions of the world potato market with continuous increasing in production and consumption capacity, but the average yield is lower than the world level. Virus-caused seed potato degeneration is one of the main reasons for low yields when seed potato production and certification systems are not strict and efficient enough. Low quality of seeds has hence become one of the major constrains to potato production in China. More than 40 viruses can infect potato crops in field and some of them cause significant diseases. Symptoms induced by various strain groups on potato are dependent on the genotypes of isolate and host, and the severity can vary broadly in intensity from very mild mosaic to very severe responses and plant death. The potato-virus interactions are less investigated and not well understood comparing with fungal and bacterial pathogens. The genetic variation within the virus and within the host, the developmental stage and physiological status of host and environmental factors all contribute to the complexity of the interactions. In this study, a novel isolate of PVY°was cloned and characterised. Together, all five PVY strains were employed to investigate the response of potato cultivars to PVY in both primary and secondary infections. To look into a possible mechanism of potato-virus interaction, the genes involved in the compatible and incompatible interactions were identified. The main results are as follows:1. A novel isolate of PVY°caused atypical severe symptoms, termed as PVY°-FL, was cloned and characterized. Analysing together with other PVY°isolates in the database, mild and severe strain subgroups were differentiated by specific primers and demonstrated by a phylogeny analysis. This is the first report describing the diversity of PVY°pathogenicity and the relationship between the PVY°genotypes and the disease severity in potato plant.2. Responses of 14 potato cultivars to 5 PVY strains indicated two types of disease symptoms, mosaic and necrotic. The results further showed that the necrosis was associated with PVY°and PVYNTN, and caused a greater yield loss in the primary infection and even more in the secondary infection.3. There were 43 genes differentially expressed during the compatible interaction between potato cv. Shepody and PVY and the incompatible interaction between this cultivar and PVA. Total 19 genes were found uniquely expressed in the compatible interaction and 2 in the incompatible while 22 shared by both the interactions. The results demonstrated some important genes and pathways involved in resistance and susceptibility which could provide useful information approaching the mechanism of potato-virus interaction. |
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