| Wheat stem rust is an airborn disease which can propagate long distance.The pathogen with its strong specialization, holotype transportation host, wide hazard scope and powerful prevalence ability lead to huge damage to wheat industry in China. It is well known that the loss of resistant ablity of wheat varieties caused by pathogen variation is the most difficult problem in proventing process. The purpose of this study is to find out a way of conquering virulence variation of the pathogen after revealing the sexual process and therefore to maintain the resistance of wheat varieties.In this study,firstly the attempt was made to investigate Berberis spp. and the aecium development on barberry in northern China,and then to inoculate cereals with aecia collected from barberry. Meanwhile, the samples of P. graminis f.sp. tritici were wildly investigated or collected from main wheat region in China, involved Yunnan, Guizhou, Sichuan and other province. Using 4 Stakman standard differential hosts,4 domestic auxiliary differential hosts and 48 resistant single-gene lines to monitoring the population dynamics and analyzing the virulence frequency of collected samples. Additionally, the resistance appraisal of 190 exotic and 100 domestic wheat materials to races 21C3, races 34C3 and a mixture of races were analyzed.1. Morphologic observation of the rust fungi on berberis and preliminary analysis by molecular biology methodsMmorphological observation was made in combination with molecular biology method to study the aecia on Berberis spp.. Cutting the aecium on barberry into frozen section using a cryomicrotome, examined the morphological structure of aecidiospore and aecium under a microscope. Extracting the genomic DNA of aecium and amplifying the DNA with fungal universal primers. After comparison analysis through NCBI, it was shown that unknown rusts accounted for 69.9%, Puccinia spp. accounted for 15.5%, P. graminis accounted for 5.6% and P. striiformis accounted for 10%.2. Population dynamic and virulence frequency analysis of P. graminis f.sp. triticiFifty five single spore isolates was separated and purified from 35 samples collected in Guizhou and identified using the above mentioned differentials. The result was indicated that 7 physiological races:21C3CKHTM,21C3CKHQM,21C3CFGSM,21C3CKGQM, 21C3CKHSM,21C3CKGSM and 21C3CKGTM were identified and they belonged all to race 21C3, and race 21C3CKHTM and race 21C3CFGSM are predominant races, the occurrence frequency is 16.4%. The single-gene Sr5, Sr9e, Srll, Sr19, Sr21, Sr26, Sr30, Sr31, Sr33, Sr35, Sr36, Sr38, Sr47 and SrTt3 proved to be resistant to all test strains. The single genes Sr7b, Sr8a, Sr9a, Sr9b, Sr9d, Sr9g, Sr9g and SrMcN were invalid to all test strains. Furthermore, there was norace Ug99 detected in this study.3. Resistance appraisal of exotic germplasms and northeast China’s wheat cultivars or lines to Chinese wheat stem rustThe resistance of 190 foreign wheat materials and 100 wheat materials from Heilongjiang province were tested with races 21C3CTHTM,34C3RTGQM and mixed races (21C3 And 34C3) of Puccinia graminis f. sp. tritici in 2015. The result was indicated that 168 of the 190 foreign wheat materials showed resistance to all the races tested, in which 118 were immune and 50 were highly resistant; among 100 wheat cultivars from Heilongjiang,71 showed resistance to all the tested races including 45 with immunity,23 with high resistance and 3 with high-medium resistance. In conclusion, all tested materials have relative high resistance to races of Pgt in China, but still some part of foreign and Heilongjiang wheat materials were found to be highly susceptible. |
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