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Improvement of Jerusalem artichoke genotypes with resistance to stem rot caused by the soil borne fungus Sclerotium rolfsii is a sustainable means for controlling the disease. However, this crop is rather new to breeders. A consensus screening procedure for resistance to the disease is not yet available. The aim of this study was to determine the level of inoculum that provides the reliable and effective results for screening trials. In the experiment in Khon Kaen, Thailand, four levels of sorghum seed infested with S. rolfsii (1, 2, 3 or 4 seeds/plant) were tested with 10 Jerusalem artichoke genotypes. Plants inoculated with one sorghum seed had the lowest disease incidence, whereas plants inoculated with four sorghum seeds had the highest disease incidence. Most pairings of inoculum levels were statistically different for disease incidence except for two vs. three seeds. In addition, permanent wilting and area under disease progress curve occurred more rapidly with four seeds compared to the other inoculum levels. The highest variation among Jerusalem artichoke genotypes was observed in the plants inoculated with three sorghum seeds. Therefore, three sorghum seeds inoculum was suitable to identify Jerusalem artichoke genotypes resistant to S. rolfsii. Based on days to permanent wilting, resistant and susceptible genotypes were identified.

Jerusalem artichoke is a perennial crop, but it is grown as an annual crop for its inulin containing tubers. Various factors affect inulin content, in which storage duration is one of the significant causes. Therefore, the effect of different storage durations on inulin content of Jerusalem artichoke was investigated in this study. Four Jerusalem artichoke varieties were assigned as factor A, and six durations of storage at 5 oC were assigned as factor B. The 24 treatment combinations of a 4×6 factorial were arranged in a completely randomized design with four replications. After harvest, the tubers were cleaned and stored at 5 oC for five months. Inulin content was analyzed consecutively at 0, 1, 2, 3, 4 and 5 months after storage. Times of storage and varieties were significantly different (P<0.01) for inulin content. Stored tubers had inulin contents ranging from 35.9 to 43.7 % compared to 47.8 % of freshly-harvested tubers. The lowest inulin content was found after 2 months of storage. JA 89 had the highest inulin content (47.80%), whereas CN52867 had the lowest inulin content (35.85%). Regression analysis showed small and insignificant effect of storage time on inulin content, and the results are discussed. The results will be useful for consumers and industries for their concern on storage loss of inulin content after storage