Species And Physiological Races Identification Of Bacterial Spot Pathogen On Tomato And Pepper In China

Bacterial Spot caused by Xanthomonas campetris pv. vesicatoria (Doidge) Dowson is a general kind of disease on tomato and pepper, and it not only significantly reduces the yields of pepper and tomato, but also seriously affects the quality of their fruits. As early as in 1960s, some researches had already suggested that there were rich phenotypic diversity of bacterial spot pathogen on tomato and pepper. In 2004, Jones and his fellows named the four phenotype groups A, B, C, D of the pathogen as X. euvesicatoria, X. vesicatoria, X. perforans and X. gardneri respectively. Moreover, the results of identification of physiological race suggested that there were eleven kinds of physiological races on pepper, and there were five races on tomato. But there are almost no relevant research reports on these aspects in China.This study was mainly to investigate clearly the distribution of the four phenotype groups of bacterial spot pathogen and physiological races in the main planting areas of tomato and pepper in China, as well as some biological characteristics. The results are following.(1) Identification and biological characteristics of bacterial spot pathogen. Pathogenicity tests, physiological and biochemical tests and ITS sequence analysis were taken, and the results showed that the 60 strains isolated from Shanxi, Shaanxi, Xinjiang and other thirteen regions were bacterial spot pathogen.(2) Classification of bacterial spot pathogen with restriction endonuclease analysis. Firstly, the genome DNA of these strains were amplified by the specific primer pairs of RST65 and RST69, and then the amplified products were digested by the restriction enzymes of HaeⅢ, CfoⅠand TaqαⅠ, and the digestion products were analyzed by agarose gel electrophoresis with the result of four kinds of restriction patterns. Compared to the type strain ICMP98 (X. euvesicatoria), ICMP63 (X. vesicatoria), ICMP99 (X. vesicatoria), ICMP16689 (X. gardneri) and ICMP16690 (X. perforans), these strains could be classified as four species, X. euvesicatoria (Group A), X. vesicatoria (Group B), X. perforans (Group C) and X. gardneri (Group D). This was the first and systematic study on the classification of bacterial spot pathogen on species level in China.(3) Identification of physiological races. These differential hosts ECW, ECW-10R, ECW-20R, ECW-30R, Hawaii7998 and Hawaii7981 were inoculated with bacterial spot pathogen, and it was found that there were tomato race T1, T3 and pepper race P0, P2, and tomato-pepper race T1P0, T3P0, T1P2, and later six races were new in China.