Study On Genetic Difference Of Eight Races In Puccinia Striiformis F.sp Tritici

Yellow (stripe) rust, caused by Puccinia striiformis f.sp.tritici, is one of the major diseases that seriously impact the wheat production around the world. The characterizations of the disease include high outbreak frequency, large infection area and server damage. It especially threatens the winter- and spring-wheat production in the major wheat production area of China. Studies have shown that breeding and deploying the disease resistant cultivars is so far the most economic and efficient strategy for yellow rust prevention. However, the lost of resistance attenuates the advantage of deploying the disease resistant cultivars. Meanwhile, it is belived that the occurrence and the development of new races of Puccinia striiformis f.sp.tritici is the pre-dominant reason for resistant lost. Therefore, understanding the genetic chracterization among the major races and epidemic strains of Puccinia striiformis f.sp.tritici becomes a very important step of preventing wheat yellow rust and developing new resistant cultivars.Puccinia striiformis f.sp.tritici has very complicated genetic background. Until now, there is no report regarding the successful culture the cell in vitro. The traditional method of races identification is complicated, time consuming and less accurate. Meanwhile, due to the limited host range, it is difficulty to differentiate and identify the races with lower infection frequency. All those limitations seriously impact the progress on studying the biology and the population structure of Puccinia striiformis f.sp.tritici. The modern molecular biologic methods provide new approachs to monitor the population and the variation of the yellow rust races in different area.In this study, the RAPD(Random Amplified Polymorphic DNA) and SSR(Simple Sequence Repeat)techniques were utilized to analyze the prevalent races of Wheat stripe rus(tCY33,CY32,Hy8,SU11-3,SU11-4,SU11-5,SU11-7,SU11-13), to identify the specific DNA fragments of the epidemic races. The results from this study will establish the foundation for monitoring the physiological races of wheat stripe rust and provide a scientific basis for breeding the disease resistant wheat cultivars. Furthermore, the gene, psCon1 was cloned from the eight major physiological races of wheat stripe rust, and the DNA sequence, the primary and the possible tertiary structure of the gene product were analyzed.The results of the study were summarized as following:1. Total 220 random RAPD primers were selected and used to analyze eight major physiological wheat stripe rust races, the results show that 167 out of 220 primers could obtain stable and clear amplification patterns. The data indicate that the genetic variation among the eight physiological races of wheat stripe rust is vast, but some genome sections still show highly conservative.2. Total 167 random RAPD primers were selected and used to analyze eight major physiological wheat stripe rust races. Identified the specific RAPD marks for CY33,CY32,Hybrid46-8,SU11-4 race four populations. A 200 bp length specific DNA fragment was amplified by using primer set S39 from CY32; a 510 bp length specific DNA fragment was amplified by using primer set S36 from Hybrid46-8; a 500 bp length specific DNA fragment was amplified by using primer set S301 from CY33; a 310 bp length specific DNA fragment was amplified by using primer set S2140 from SU11-4. And according to the sequence of the RAPD fragments from CY33 and SU11-4, the specific PCR primers were designed and used to amplify the SCAR markers3. The DNA polymorphism of 8 prevalent stripe rust races was analyzed by using 20 pairs of specific primers. The results show that all primers could detect polymorphisms among races, and variations existed among races. A 170 bp length specific DNA fragment was amplified by using primer set RJ20 from SU11-5. Two, 220 bp and 480 bp length specific DNA fragments were amplified by using primer set PS305 from Hybrid46-8, a 220bp fragment from SU11-7. Two, 220 bp and 238 bp, length specific DNA fragments were amplified by using primer set SW440/ SW 441 from Tiaozhong32. A 230 bp length specific DNA fragment was amplified by using primer set PS2091 from SU11-4. All those fragments are repeatable.4. Cloned and isolated the spore producing gene, psCon1, from 8 races. The analysis of DNA sequence and protein structure indicate that only few point mutations were detected among races, only one point mutation was located on exon, and it is a salient mutation.5. The concentration of copper and plumbum in infected leaves of Tianlan-26(Rust-resistant cultivar)and Mingxian-169(Rust-susceptible cultivar) were analyzed by atomic absorption spectrum analyzer. The results indicated that the concentration of both copper and plumbum in inoculated leaves of Lantian -26 and Mingxian-169 were increased at early stage, and then declined gradually. The data also revealed that the concentration of copper and plumbum from the disease-free leaves of Lantian-26 and Mingxian-169 did not show variation during the test stages.As summary, the above results indicated that RAPD is a very suitable method for analyzing, the genetic relationship of Puccinia striiformis f.sp.tritici;and searching the special marker for Puccinia striiformis f.sp.tritici races by SSR. both methods could be supply reference and helping to establish a molecular identification system and simplify th distinguish program of the Puccinia striiformis f.sp.tritici races by means of cosmically searching special fragments of yellow rust races.