Study On Genetic Diversity Of Some Accessions Of Chinese Wheat Germplasm And Molecular Marker Assisted Selection For Powdery Mildew Resistance

Study on wheat germplasm could provide foundational information required in wheat improvement and genetics. In the present paper, the procedure suitable for wheat AFLP (amplified fragment length polymorphism) fingerprint analysis was explored, and the fingerprints of some accessions of common wheat (Triticum aestivum L.), including wheat major progenitors in wheat breeding, commercial varieties with large annual planting area, and some accessions of special germplasm, were established. The genetic diversity distribution of ecological regions and planting decades was analyzed. With the AFLP technique, we survyed the near isogenic lines with different resistance genes to powdery mildew, which were cultivated by Key Laboratory of Crop Germplasm & Biotechnology subordinated to Ministry of Agriculture, Institute of Crop Germplasm Resources, Chinese Academy of Agricultural Science. The genetic similarity to recurrent parent was evaluated and their prospect in future application was confirmed. A new resistance gene to wheat powdery mildew was identified, and molecular markers linked tightly to the resistance gene were found. It was proved to be feasible to select the resistant plants similar to the recurrent parent in backcross, and this would promote the development of near isogenic line for powdery mildew resistance and the exploration for new resistance genes.1. The AFLP fingerprint of 259 accessions of common wheat were established with the methylation sensitive enzyme combination Mse I -Pst I . In total, 245 polymorphic bands were detected. The primer combination M-CAC/P-ACA could identify 97 percent of the accessions, and some accessions could be identified by the characteristic bands. The appropriate number of AFLP polymorphic bands for varieties identification varied the 50 percent (1/2γ) to 100 percent (γ). The minimum number of polymorphic bands in large accessions identification should be up to 80.2. In the major progenitors in wheat breeding, the landraces showed distinct genetic difference. The narrow genetic base of commercial varieties with large annual planting area was detected. Since early 1950s, the genetic diversity of Chinese wheat had come through a trend like "V", with the highest in early the 1950s, and after this, the genetic diversity level tended to descend, to the lowest in the 1960s. Since the 1970s, the genetic diversity began to come back, but by now, there has been a fall in genetic diversity compared with early the 1950s.3. Greater genetic diversity was found in South China winter wheat region. Compared with modern cultivars and introduced accessions, greater genetic diversity was observed in landrace. Besides, winter ecotype showed greater genetic diversity than spring ecotype. Great genetic differentiation was found between winter and spring ecotype.4. Great genetic variance was detected in non-recurrent parents of the near isogenic line to powdery mildew, and good genetic consistency was found in the NILs.5. Characteristic bands of the resistance gene to powdery mildew Pm21 and Pml3 were found, which could be used in the identification of the disease resistance genes and near isogenic lines.6. Several AFLP markers linked tightly with a new resistance gene were found. These markers were distributed around the resistance gene. Several disease resistant plants genetically similar to the recurrent parent Bainong3217 were selected with the AFLP technique, and greater efficiency could be expected when selected these plants in backcross.