The Situation Of Bacterial Fruit Blotch On Watermelon And Melon In China And The Detection Of The Pathogen From The Seeds

Bacterial Fruit Blotch(BFB) caused by Acidovorax avenae subsp. citrulli (Aac) which is an important national plant quarantine disease in China is a destructive disease on watermelon and melon. The disease is seed-borne and seed transmitted. As the rapid development of science and technology in agriculture and international trade in recent years, the exchange and the long-distance transportation of melon germ plasm resources become more frequent, for what the disease has seriously threatened the development of watermelon and melon production in China. The study undertaken has following objectives: to know the growing areas of the melons and the occurrence situation of BFB in China; to develop an accurate, rapid and sensitive method to detect the pathogen in the seed quarantine for effective management of the disease.At present study, a great deal of information was collected and concluded that either the planting area or the yield of watermelon and melon that has become the important international competitive horticulture industry with great economical rise in China was the largest in the world. It is reported that the watermelons in 10 provinces in China have suffered from BFB in recent years, and especially in Xinjiang, Inner-Mongolia, Fujian and Taiwan province, the disease caused significant economic losses for farmers. The investigation also showed that there's no immunity cultivar against BFB, although the resistance varies with varieties of the melons. The outbreak of BFB was affected greatly by the weather. The more rainfall and the higher temperature during the melon growth period, the more serious the disease was.An immuno-capture polymerase chain reaction (IC-PCR) method for detection of Acidovorax avenae subsp. citrulli has been established in 2006 in our lab. The minimum detection concentration for the IC-PCR was about 50-100cfu/ml, which is 100 times higher than that of direct PCR method. The present study found that MOPS buffer is more effective for extraction compared with another buffer when the seeds were incubated at 28℃(220rpm) for 4 hours. IC-PCR detection was performed by immersing diseased seeds in different buffer. When 20 seeds were added into 2ml buffer, Aac could be detected in different buffer; however, when 1 of the seeds were added into 1ml buffer, Aac could be detected only in MOPS buffer. Therefore, it seems that the sensitive of detection could be improved when immersing the seeds in MOPS buffer. The distribution of Aac on the seed was determined and most of them were colonized on seed coat and no bacteria were detected on seed kernel. The detection of melon seeds from market of Hangzhou were performed and the result showed Aac was present on cultivar Zhemi-4 and Zaojia 84-24 from Xinjiang and cultivar Shoushanwang from Taiwan, therefore, it should be pay attention to the potential risk of Aac on production of melon and watermelon in Zhejiang.