| Mainly 3 parts were studied on this thesis; they were Pest risk analysis (PRA) and detection techniques of Erwinia amylovora and susceptibility of some rosaceae plants in China to fire blight. I. PRA of Erinia amylovora to China Based on LSPM and combined with the situation of China, PRA system initiated by a pathway and initiated by a pest were developed. According to the characteristics of port quarantine, a quick PRA system was constructed for PRA of intercepted pests. Constructed PRA systems were validated and used to PRA of Erwinia amylovora. PRA system were composed by 4 stages, there are 1) initiation, 2) pest risk assessment, 3) pest risk management and 4) pest risk communication. The risk of commodity itself was considered on the PRA initiated by a pathway. After determined the risk of commodities to become weeds or plant pathogens, PRA of pest carried by commodities will be started. General formula on biosafety evaluation, R=f(S, F) was used for processing pest risk assessment in plant quarantine. The general formula was simplified as R=SXP, could express objectively the relationship among the risk related factors. According to the value of R, risk rank of pests was partitioned for 4 classes; from high to low they were very high, high, middle and low. Suggested that the pest belong to middle and above should be managed by quarantine actions. PRA system initiated by a pest, is only different in the first stage from that initiated by a pathway, the rest stages are the same. Using the published data related to PRA, constructed systems were validated primarily. Results show that the constructed systems were reasonable and workable. Based on the selected dada and experiment, utilizing the constructed PRA system, the risk of Erwinia amylovora to China was processed. According to calculated value of R (10.018), Erwinia amylovora was belonged to the very high- risk pest. 2. Primary exploration of susceptibility of same rosaceae plants in China to fire blight Seedlings, flowering shoots, tender shoots and immature fruits of 9 genus 18 species were collected and their susceptibility to 3 Erwinia amylovora strains was explored. Results show that pear has higher susceptibility than apple; Chinese white pear, European pears and P betulaefolia are more susceptible than sand pear; susceptibility of other tested rosaceae plants is lower than pear and apple. Susceptibility of flower and young fruit is higher than shoot and seedling. All tested pears inoculated in viva are affected by Erwinia amylovora. Flowers of all tested pears and apples inoculated in vitro are susceptible to Erwinia wnylovora. Immature pear fruits inoculation test shows that susceptibility of young fruit, flower and seedling is coincident. The best method for evaluating resistance of pear is seedling inoculation in vivo. Inoculation results of flower and fruit plug are uniform as that of half-fruit. Flower inoculation method is limited by flowering period and could use only in very short stage. Plug inoculation is superior to half-fruit method for only needs few fruits and can be statistic. Shoot inoculation data show that virulence of Erwinia amylovora strains for high to low is 0056, Ea and 0036 and immature fruit inoculation indicates that 0056 and Ea strains have the equivalent virulence higher than 0036. Inoculation in viva by 0056 strain displayed that sensitivity of pear and apple from high to low are: Duli, Xiangyabai, Suli, Yali, Zaosu, Bartlett, Clapp Favorite, Aidang, Golden 20 century, Xinxing, Fengshui and Fucui (apple). Inoculation test shows t...
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