Genetic Diversity And Detection Of Resistance Genes To Wheat Powdery Mildew (Blumeria Graminis F. Sp. Tritici) In Wheat (Triticum Aestivum) Cultivars Or Lines

Common wheat(Triticum aestivum L.) is one of the most important crops currently grown in most parts of the world. Production is highly challenged by diseases such as wheat powdery mildew caused by Blumeria graminis f. sp. tritici(Bgt). Control of this disease remains a high priority in breeding programmes. In view of this, three studies were conducted to(i) assess the genetic diversity of sixty wheat cultivars or lines using microsatellite markers,(ii) assess the resistance of wheat cultivars or lines to infection of 20 Bgt isolates and(iii) detect the resistance genes in the cultivars or lines using molecular markers.The results on genetic diversity of 60 cultivars or lines showed that 276 alleles were amplified by 48 polymorphic microsatellite markers averaging 5.7 alleles per locus. Polymorphism of alleles and genetic diversity measured by Polymorphic Information Content(PIC) and Shannon Index(SI) respectively indicated that genome A was the most genetically diverse followed by genome B while genome D was the least. Similarity analysis using Un-weighted Pair-Group Method with Arithmetic Average(UPGMA) resulted in formation of four clusters comprising of 3, 7, 9 and 41 cultivars or lines. This suggests to the breeders that the backgrounds of most of the 60 cultivars or lines are similar.Results on greenhouse study found that cultivars Keyuan5, Xinmai19, Tianmin198, Yanzhan4110 and Bainong160 carried Pm4 b resistance gene. Yujiao0338 carried Pm4 a, Zhongyu885 carried Pm8 and Lankao008 carried Pm4+8/Pm4b/Pm30 genes. Tian00127 and Guomai301 were highly resistance to all 20 isolates. Cultivars; Keyuan5, Lankao008 and Tianmin198 showed resistance to 17 isolates while cultivars Tian01-104, 05bao1-1, Tian0015 and Yanzhan4110 were resistant to 16 isolates. Among the cultivars or lines with known Pm genes, Wembley, R4 A, Brigand, MIN and Yangmai5/Sub.6V carrying genes Pm12, Pm13, Pm16, Pm1c=18 and Pm21, respectively expressed high resistance to all 20 isolates. In the molecular study, cultivars Xinxuan2039, Lankao008 and Zhengmai366 were detected with multiples Pm2+Pm4b+Pm8 genes while Yumai368 carried multiple Pm2+Pm4b+Pm6 genes. Seventeen cultivars including Tian01-104, Tian0015 and Xinyumai836 were detected with Pm2 gene. Twenty four cultivars, which included Zhoumai19, Keyuan5 and Xinmai19, were detected with Pm4 b gene. Two cultivars; Yumai 368 and Guomai 301 were detected with possible Pm6 gene while 24 wheat cultivars carried Pm8 gene.The results provide a significant contribution to wheat breeding for resistance to wheat powdery mildew disease since the identified resistant cultivars in the study as well as those detected with Pm genes will contribute to further efforts on improving wheat resistance to the disease. Also, the continued resistance of cultivars with known resistant genes is an indication that the responsible Pm genes are still effective in overcoming powdery mildew infections. Most of the tested cultivars or lines carried Pm2, Pm4 b and Pm8 genes. All these results will be of great significance to breeders for disease resistance breeding and rational use of cultivars and resistance genes.