Investigation And Genetic Diversity Of Wheat And Barberry Rust In Xinyuan County, Xinjiang

Wheat stripe rust,caused by Puccinia striifonrmis f.sp.tritici(Pst),is one of the most important wheat diseases around the world,caused heavy losses on wheat production in China in epidemic years.Pst is an obligate biotrophic fungi with high virulence variability,and the virulence variability is the major reason for disease outbreak.So it is important to control effectivelythe disease by knowing its population genetic structure and epidemic rules of wheat stripe rust.The Pst population of China has been reported to be a distinct genetic group with higher diversity than those in many other countries.Genetic recombination in the Pst population has been identified with molecular markers.Berberis spp.play an important role in sexual generation of Pst as alternate host,but the extent and rule of sexual stage in natural conditions is still unknown in China.Wheat stripe rust occurs annually in Xinjiang Autonomous Region located in northwest of China,where there are the complexity of geographical environment and a large amount of wild Berberis spp.However,the knowledge of genetic diversity of Pst population in this region and the relationship of inoculum sources of Pst between Xinjiang and other regions are absent at present.In this study,we investigated the rust-infected on B.heteropoda Schneid and spring wheat,and the genetic diversity and virulence variation of Pst population in Xinjiang,so as to improve strategies for the control of wheat stripe rust in China in the future.1.The occurrence of stripe rust was investigated on B.heteropoda Schneid,susceptible wheat cultivars growing in the clump of B.heteropoda Schneid and field spring wheat in 2013-2015.The results indicated that rusts on B.heteropoda Schneid occurred in April 25 to May 8 and the peak-occurrence in late May to early June.Stripe rust on wheat cultivars Morocco under the clump of-B.heteropoda Schneid occurred in June 15 to June 20 and the peak in midium July,and that in farmer's fields in June 3 to June 8 and in late June,respectively.The beginning and peak time of stripe rust on wheat were significantly delayed for more than 30 days than that on B.heteropoda Schneid.Pst on B.heteropoda Schneid was identified at a rate of 4.7-5.7%by means of molecular marker specific to Pst species.Some difference in the occurrence of wheat stripe rust on B.heteropoda Schneid and wheat were attributed to the local temperature and precipitation during May to August in different years.2.The interactive inoculation experiments with Berberis rust and wheat stripe rust were conducted in the greenhouse under the controlled conditions.The results showed that,under artificial inoculation condition,the asexual and sexual of Pst can be completed on wheat and B.heteropoda Schneid,respectively,which involved in five different spore stages.Wheat with Pst urediniospores cultivating at a temperature of 20? for 10 days can produce teliospores,teliospore germinated and produced basidiospores at 16? for 96 hours in dark,basidiospores germinated at 10? for 72 hours in dark,and infected the leaves of Berberis host.After 35 days the pycnia with pycniospores grew in the upper side of Barberis leaves,and then the aecia with aeciospores developed in the back side of Barberis leaves after 10 days.Aeciospore at 10? for 48 hours in dark germinated and infected wheat leaves resulting in the production of uredia and urediniospore.Therefore,a history of Pst life cycle with sexual and asexual phases was completed.This result suggested that B.heteropoda Schneid can work as the alternate host of Pst but its role in pathogenic variation of Pst and epidemiology of wheat stripe rust is still opened.3.Using Mapk1,Cdc2 and Tub as target genes,the SNP and races of 293 Pst isolates collected from Xinjiang,Gansu and Hubei during 2013-2014 were identified.It has been found that there exist significantly differences in population structure,genetic diversity and race combinations of Pst between Xinjiang,Gansu and Hubei.The genetic diversity of Pst population in Xinjiang is higher than that in Gansu and Hubei based on the molecular diversity indices and race pattern.Similar phylotype diversity and recombination event in Xinjiang and Gansu probably arised to occurrence of Pst sexual stage onBarberis spp.in those areas.The phylogenetic tree of Pst population was constructed and UPMGA(u.nweighted pair-group method with arithmetic means)clustering analysis showed that the isolate haplotypes from different regions were clustered together,and same gene evolution direction of Pst isolates occurred in Xinjiang,Gansu and Hubei.This suggested that some gene flow exist between Xinjiang and the mainland of China.