| Stripe rust is a wheat disease caused by Puccinia striiformis f.sp.Trittici. Its frequent occurrence and worldwide spread seriously threaten wheat production. Longnan, in Gansu province, is a major over-summering region of stripe rust in China. Every fall and spring a large number of spores are spread out from this region to the eastern part of China. Moreover, this region is one of the most important birthplaces of tripe rust toxicity variation. Population diversity of wheat resistance genes in over-summering regions affects virulent genes and virulence variation. Therefore, to identify the diversity of resistance genes in these regions is helpful for further study the effect of resistant population structure on stripe rust population virulent diversity, which can also provide vital theoretic proves for reasonable use of resistance genes and guidance of wheat resistance varieties breeding in order to control the stripe rust in a national level.In this study, 83 accessions of frequent used wheat cultivars were collected from southern and eastern part of Gansu province. These cultivars were inoculated respectively by stripe rust CYR33 and CYR32 in seeding stages and inoculated by mixed races (CYR23, CYR25, CYR29, CYR31, CYR32, CYR33, Su11-7 and Su11-4) in adult stage. Meanwhile, these wheat cultivars were also infected naturally in Tianshui. In these three different circumstances, the resistance to stripe rust of these wheat varieties are separately evaluated. Several common molecular markers were used to detect the stripe rust resistance genotype, including Yr5, Yr10, Yr15, Yr24/Yr26, Yr9, Yr17, Yr18. Combined with the results of breeding pedigree analysis, resistance screening and molecular detection, the stripe rust resistance genes may be carried by every wheat variety were studied. Population structure of the resistance genes in wheat varieties of Tianshui region was analysed preliminarily according to the plant areas of each wheat variety in this region between 2005 and 2009. The main results of this research are as follows:1.Evalution of resistance to stripe rust. In seeding stage, 53 wheat varieties have resistance to stripe rust CYR32 and 30 varieties are susceptible to stripe rust CYR32. However, 59 varieties are resistant to stripe rust CYR33, 24 varieties show susceptible to stripe rust CYR33. 42 varieties show resistance to both stripe rust CYR32 and stripe rust CYR33, while 14 varieties are proved to be resistant to these two stripe rust races simultaneously. Stripe rust mixed races inoculation in adult stages and natural infection in Tianshui showed that among the 83 tested wheat materials, including the complete susceptible and slow rust, 34 wheat materials are susceptible, accounting for 41%, whilst 23 accessions have adult plant resistance, accounting for 27.7%.2. Molecular test and resistance gene analysis. Use markers of known genes, 83 wheat materials were conducted molecular detection, anti-spectral identification and breeding pedigree analysis, the results showed that of the 83 wheat materials tested, 8 accessions have Yr5, which account for 9.64% ; 18 accessions have Yr9, which account for 21.68% ; 8 accessions have Yr15, accounting for only 2.4% ;15 accessions have Yr17 , accounting for 18.07%; 15 accessions have Yr18, accounting for 18.07%; 7 accessions have Yr26, accounting for 8.43%; Yr10 were not detected in these wheat varieties. A conclusion can be drawn from this data, Yr5, Yr10, Yr15 and other effective resistance genes such as Yr24/26 are not evenly distributed.3. Population structure study of wheat resistance genes in Tianshui Longnan core summering region. According to data from the major wheat plant area between 2005 and 2009 supplyed by the Tianshui agricultural department , the population structure of wheat resistance gene were annlysed. The results showed plentiful disease resistance genes are carried by wheat varieties from Tianshui. Wheat varieties with Yr17 are used more widely than any other wheat varieties. Interestingly, wheat varieties with Yr26 are used increasingly frequently these years. Wheat varieties with Yr5, Yr15 or Yr10 only was planted in a small portion of the total area; More seriously, wheat varieties with durable resistance genes Yr18 varieties are cultivated in a gradually decreasing area. In addition, some unknown source of resistance genes are used, such as Guizhou series and Thinop Yrum intermedium derived resistance. This study shows that although many types of anti-source are used in this region, only a few resistance genes are carried by the mainly used wheat varieties. Particular, Yr26 has been widely used, which should be highly valued, to avoid producing the problems of some resistance genes, like Fan6 and Yr9. |
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