Studies On Genetic Polymorphism And Spatio-temporal Dynamics Of Puccinia Striiformis F. Sp. Tritici In The South Of Gansu Province

Wheat stripe rust caused by Puccinia striiformis f.sp.tritici, is an important aero-borne foliar disease of wheat distributed in most areas of the word. South of Gansu is not only the most important over-summering areas of P. striiformis f.sp.tritici but also a variable zone of rust race or virulence and wheat cultivar resistance to stripe rust. It plays an important role in the epidemiology of wheat stripe rust in China. In recent years,epidemic law including over-winter and over-summer of wheat stripe rust had changed duing to global warming, changes in cultivation system and variety distribution. Our research consisting of three aspects namely field survey, virulence analysis and genetic polymorphism to verify the inoculum communication of different mountain areas, was conducted in Tianshui area, Gansu province. Research result will be useful to the disease epidemiology and control in the over-summering areas. Results of our research are as follows.The results of field survey indicated that the severity of stripe rust on the same wheat variety (Mingxian 169) increasing with the decreasing of the altitude in the autum, but in spring it just showed the opposite trend. The local inoculum sources are the major causes of the disease epidemics in the spring. The wheat stripe rust could successfully overwinter in the areas of 1293-2080m in the general years, and the overwintering rate of the pathogen displayed increasing with the decreasing of the altitude although there are some differences in the overwintering rate year by year. Compared with the past results from 1950s to 1960s, the upper limit of altitude for the overwintering of P. striiformis f. sp. tritici has markedly raised by 300m in that areas, probably attributed to the temperature rising during the overwintering period of P. striiformis f.sp.tritici in that area.39 near-isogenic lines and 8 pairs of SSR primers were employed for the virulence and SSR genetic polymorphism analysis of 66 P. striiformis isolates from the different altitutes areas in Tianshui, Gansu province. Results indicated that the population of wheat stripe rust in that region had high virulence frequency of 55.4%-100.0% to the majority of the wheat stripe rust resistance genes except Yr5, Yr24,Yr26, Yr10 and YrMoro with the virulence frequency of 0-1.5% respectively. By utilizing NTSYSpc version 2.10 software, the virulence and genetic polymorphism of 66 isolates were analyzed. It was found that high diversity existed in all of 66 isolates tested with the similarity coefficient of 0.46-1.00 for virulence, and 0.41-1.00 for SSR partern. The similarity of virulence frequency and genetic polyphorphism of P. striiformis isolates from the different altitude areas indicated that high frequency of pathogen exchenge could occur in south of Gansu. Compared with virulence polymorphism and SSR polymorphism, it showed low relevant with the similarity coefficient of 0.02931.The results above-mentioned would provide a valuable aid to the deployment of wheat varieties and monitoring of pathogen dynamics in the south of Gansu province.