Selecting the Pyramids of Powdery Mildew Resistance Genes Pm4b, Pm13 and Pm21 in Wheat Assisted by Molecular Marker

Pyramiding resistance genes have been suggested as one of the most effective methods for preventing breakdown of major gene conferring resistance to powdery mildew within a very short period. The PCR markers of the powdery mildew resistance gene Pm4b, Pm13 and Pm21 were used to identify the genes in F 2 plants of combination among the wheat lines containing Pm4b, Pm13 and Pm21 respectively. The results indicated that all the plants containing any one gene, two genes or three genes of Pm4b, Pm13 and Pm21 showed resistance to powdery mildew, while the plants lacking the resistance gene were susceptible to powdery mildew. The tightly linked markers of the resistance genes were powerful tools for the identification of Pm4b, Pm13 and Pm21 in breeding program. Eleven plants pyramiding three genes of Pm4b+Pm13+Pm21, 10 plants pyramiding Pm4b+Pm13, 6 plants pyramiding Pm4b+Pm21, and 3 plants pyramiding Pm13+Pm21 two genes, were selected from 40 plants of the F 2 population. They can be used as parents to breed wheat for powdery mildew resistance. The results reconfirmed that the stability of a resistance gene is closely related to the relationship between donor and receptor of the gene. The study showed that molecular marker selection has more advantage than the traditional phenotype detection especially in wheat breeding for pyramiding of resistance genes.