Resistant Gene Control And Related Mechanism To The Invasion Of Race Ug99 Of Puccinia Graminis F.sp.Tritici

Wheat stem rust is a catastrophic wheat disease because of its ability to cause complete annihilation of wheat crops over wide areas.China is in special wheat stem rust epidemic region and had suffered from many times of devastating wheat losses due to the stem rust.For nearly four decades this disease has been controlled internationally by widespread use of the 1BL.1RS translocation with Sr31.Race Ug99(TTKSK) with Sr31 virulence was first detected in Uganda during 1999 and become a new threat to wheat production,it not only is susceptible to most of worldwide leading cultivars,but is disseminating very fast.It confirmed that this race had moved to Iran and Pakistan in 2007.Ug99 could be called a supper virulent race to widely used and Sr31-carrying Chinese wheat,if the race invades into China,it could not be able to predict how missrable the consequences will be.So in order to prevent our wheat production from bad losses,the urgent researches would be included in the following aspects:(1)Race dynamics were monitored in China and effective genes resistant to domestic races and Ug99 were analyzed and selected.(2)Breeding germplasm resistant to Chinese races and Ug99 were selected.(3)Two SSR markers tightly linked with Sr33 were screened and one closer than reported SSR marker linked to Sr22 was screened.(4)For the first time some SSR markers of effective resistant genes resistant to Ug99 were used to detect stem rust resistant genes contained in 150 wheat varieties.(5)Resistance mechanism of wheat was analyzed according to gene for gene theory,elicitors from intercellular washing fluids (IWFs) in incompatible interaction were obtained.The main progresses were as follows:1.102 isolates from the main epidemic region in China were identified during 2006-2008 using compound differential host system.Three race pathotypes 21C3CTH,34MKG and 21C3CFH were identified and their frequencies were 62.8%,9.3%and 27.9%respectively in 2006 to 2007.Four pathotypes 21C3CTH,34MKG,21C3CFH and 21C3CPH were identified with frequencies of 72.9%,16.9%,6.8%and 3.4%respectively in 2007 to 2008.It was shown that wheat stem rust occurred in a negligible amount nationwide in the two years,only a few race pathotypes were found,without finding new pathotype Ug99 at present.21C3CTH still remained predominant.2.The virulence spectra of 21C3CTH,21C3CFH,34MKG and so on were determined on 47 single gene lines.The comparison of virulent genes carried in Chinese common races and those contained in Ug99 was conducted,it was indicated that the resistance of Sr5,9e,11,21, 30,31 and 38 which conferred better resistance in China could be overcome by Ug99 and the genes Sr22,26,33,35 and 37 could be adopted in breeding because of their resistance to both Chinese races and Ug99.3.92 CIMMYT wheat materials resistant to Chinese stem rust races and Ug99 were selected using races in China and Ug99 in Kenya.328 breeding lines from Heilongjiang province showed good resistance,97.0%of them at adult plant stage and 91.2%of them at seedling stage were resistant to main Chinese pathotypes,52.0%of 150 cultivaries from China also had good resistance.Resistant breeding materials could be selected by resistance appraisal conducted both in China and in in Kenya.4.Sr22 and Sr33 not only confer resistance to majority of Chinese races but also to Ug99. Two SSR markers Xwmc790 and Xwmc633 were identified to be tightly linked to Sr22 using bulked segregant analysis(BSA),and mapped on the distant side of centromere,with distances of 2.8 and 10.8cM respectively.Further the polymorphic fragment was recovered, cloned and sequenced,Xwmc790 amplified mareker allele with size of 105 bp on resistant parent.Two codominant SSR markers Xbarcl52 and Xcfdl5 were also identified to be tightly linked to Sr33,Xcfdl5 was mapped on the near side of centromere with the genetic distance 2.1cM and MarkerXbarcl52 was mapped on another side of the gene with the genetic distance of 2.4cM.Marker Xcfdl5 amplified 161bp band mareker on resistant parent.5.To validate the function and polymorphism of available SSR marker,some SSR markers such as Sr6,Sr22 and Sr25 resistant to Ug99 were tested by agarose gel electrophoreses.It was shown that Xcfd43,Xcfa2019,Xwmc790 and Xwmc221 could be used for related resistant gene detection.The resistant genes in 150 Chinese wheat varieties were detected using these markers,ten varieties in Heilongjiang province were found to contain Sr6,two varieties were shown to carry the Sr22 and none of them was identified to contain the Sr25.6.The research of interaction between wheat and stem rust showed that 02-,POD and PAL had a tightly relationship with wheat resistance to stem rust.Intercellular washing fluids (IWFs) were extracted from highly incompatible interaction wheat leaves after inoculation and were proved to have eliector activity.Through ammonium sulfate precipitation the elicitors were concentrated by 50%~80%classification which could induce HR and increase PAL and POD activity.Eliciting activity of IWF80 did not diminish using trypsin or boiling but lossed completely after treatement by sodium periodate,which showed that the carbohydrate residue was probably the active site in IWF80.