Syudy On Function Of Rusted Barberry Adjacent To Wheat Fields In Occurrence Of Wheat Stripe Rust

Wheat stripe rust,caused by the Puccinia striiformis f.sp.tritici(Pst),is one of a major disease affecting safety of wheat production worldwide.The lose of resistance of wheat cultivar was major reason for rapid variation of Pst pathogenicity.Among many ways contributing to cause pathogenicity variation of Pst,sexual reproduction is most important.Recently,barberry(Berberis)was confirmed to serve as the alternate host for Pst,making possible to carry out sexual reproduction-relevant studies.So far,many species in genus Berberis native to China were identified as sexual(sexual)host for Pst.Based on our investigations in recent years,barberry bushes growing nearby wheat fields was very common in different regions in China.It was also universal that barberry tissues,especially leaves,were infected by rusts to produce aecia.Pst isolates were recovered from rusted tissues of barberry species,indicating a fact that sexual reproduction of Pst exists in China under natural conditions.However,no direct evidences suggest that barberry play an important role in the occurrence of wheat stripe rust.Therefore,in this study,we obtained Pst isolates from rusted barberry and wheat plant growing nearby the rusted barberry bushes and analyzed the Pst isolates,and expected to reveal the role of barberry in occurrence of wheat stripe rust.The results were as follows:1.Production of aecia and release of aeciospores,as well as occurrence of stripe rust on wheat matched in phenology.The field surveys showed that it is very common that barberry growing around wheat fields in Baoji,Shaanxi.In late the middle 10-day of April,barberry began to be infected sporadically(pycnial stage).Up to the last 10-day of April,pycnial lesions produced much more than middle 10-day of April.In the early of May,aecia were visible on barberry.Simultaneously,uredium of stripe rust produced on leaves of wheat plants growing nearby the rusted barberry bushes were not observed.In early the middle10-day of May,stripe rust infections on wheat plants growing the rusted-barberry were observed.2.Pst isolates were successfully recovered from rusted barberry and wheat nearby the rusted barberry.In the spring of 2016,103 Pst isolates were obtained from rusted barberry in Baoji of Shaanxi,in which 229 Pst isolates were acquired from wheat nearby the rusted barberry after aeciospores released from barberry.Additionally,116 Pst isolates were recovered from wheat in this region in the autumn of 2015.3.Pst isolates-derived from the rusted barberry composed of various race types,including current known dominant races and new races.Virulence of all of the Pst isolates were identified on the Chinese differential hosts and the single Yr near-isogentic lines,respectively.The results showed that 103 Pst isolates produced 57 different race types based on tests on the Chinese differential hosts,including 12 current known race types,mainly including Guinong 22,Hybrid 46 and Suwon 11 pathotype group,and 45 new race types.Among the 103 Pst isolates,58 races were known dominant races,accounting for 56.3%(58/103),and 45 races belonging to 45 various race types were new races types,accounting for 43.7%(45/103).The results based on tests on the single Yr near-isogentic line showed that 103 Pst isolates gave rist to 75 different virulence patterns.A total of 34 virulence patterns were identified from the 116 isolates obtained from the autumn-sown wheat in 2015 based on the tests on the single Yr near-isogentic lines.4.Pst population-derived from the rusted barberry and Pst population-derived from wheat fields nearby to the rusted barberry bushes represented high genetic diversity and shared the same gentotypes.Fourteen SSR primers were screed and used for molecular analysis for the Pst populations.The results showed that there were 54 genotypes of 103 isolates from barberry,71 genotypes were found in 107 isolates in the spring of 2016(Selected from 229 isolates)and 23 genotypes were expressed in 55 isolates in the autumn of 2015(Selected from 116 isolates).Among them show that 7 identical genotypes appeared simultaneously in the barberry group(include 40 genotypes)and the 2016 spring group(include 23 genotypes).And there have 4 identical genotypes appeared simultaneously in the 2016 spring group(include 18 genotypes)and the 2015 autumn group(include30 genotypes).These results suggested that the infected barberry provided effective inoculumn sources to trigger occurrence of stripe rust on wheat nearby the barberry bushes.The diversity of Pst races in spring was more abundant than that of autumn.It also provide a direct evidence that barberry play an important role in the epidemic of wheat stripe rust,improved the epidemic system of wheat stripe rust,and provided an basis for making new strategies for control of wheat stripe rust in China.