Molecular Genetic Structure Of Wheat Stripe Rust Population In 8 Provinces Of China

Wheat stripe rust,caused by Puccinia striiformis f.sp.tritici(Pst),is one of the most destructive diseases that arised wheat yield losses in China annually.China has an independent and complete epidemic system of wheat stripe rust in the world.The pathogens can overwinter and oversummer in different regions,and transmitted by long distance airflow resulting in spring epidemics.Many studies have shown that South of Gansu and Northwest of Sichuan are the most important inoculum sources and the reservoir of new races of Pst in China,which provide inoculum of wheat stripe rust for winter wheat in wide areas in China in autumn.However,the epidemics of wheat stripe rust in China in 2017 showed different characteristics from this knowledge,which put forward a need for a more comprehensive understanding of pathogen sources of wheat stripe rust population in China under the new situation.Based on the occurrence of stripe rust in 2017,the purpose of this research was to analyze the cause of stripe rust epidemics in 2017,and to understand the genetic diversity of stripe rust population in different regions and the inoculum relationship between different regions.In this study,a total of 770 uredinial samples of wheat stripe rust from eight provinces e.g.Yunnan,Guizhou,Sichuan,Gansu,Shaanxi,Shanxi,Hubei and Anhui provinces in 2017 and 2018 were analyzed by using microsatellite molecular markers and molecular genetic methods.The main results are as follows: 1.The genetic diversity of wheat stripe rust population in 8 provinces above-mentioned of China was identified: the genetic diversity of stripe rust population in Gansu was the highest,and that in Hubei was the lowest.The pathogen population in Yunnan,Guizhou and Sichuan had the similar genetic diversity,and that of Sichuan was a little bit higher.The genetic diversity of stripe rust population in Shaanxi was second place which was only lower than that in Gansu.The population of stripe rust in Shanxi also had high genetic diversity.Although the population of stripe rust in Anhui had high genotype diversity,the gene diversity of stripe rust in Anhui was low,which was only higher than that in Hubei.2.Linkage disequilibrium analysis indicated that the population of stripe rust in China basically showed the characteristics of asexual population.However,Gansu population had different characteristics from other areas.Although it can be not divided into the complete linkage equilibrium way,the results of molecular genetic analysis and the alternate host survey suggested that the population of stripe rust in Gansu could complete sexual reproduction,but the proportion of sexual reproduction and its role in disease epidemics is still opened.3.The Analysis of MOlecular VAriance(AMOVA)of stripe rust population from eight provinces showed that most of the genetic variation was existed within samples,but the differences among areas was also significant(P=0.001).4.Based on the nei's distance,12 populations were divided into two groups in 0.03 difference.The populations of stripe rust from Gansu,Shaanxi,Sichuan and Shanxi were clustered into one group,and that from Yunnan,Guizhou,Hubei and Anhui were clustered into another group.5.The results of shared genotype,genetic identity and Minimum Spanning Network(MSN)showed that the population of stripe rust in Hubei-Anhui region was more similar to that in Yunnan-Guizhou region.Those provide a molecular evidence that the inoculum sources of wheat stripe rust epidemics in China in 2017 was most likely originated from Yunnan-Guizhou region.6.It is proved that there is a wide exchange of inoculum sources in Yunnan-Guizhou-Sichuan region,and more frequently in Yunnan-Guizhou region.The population of stripe rust between Gansu and Sichuan also displayed exchange of inoculum sources.Analysis results of population genetic structure suggested that Sichuan region probably play an intermediate role in the exchange of inoculum source between Gansu and Yunnan-Guizhou.