Development Of Trigeneric Germplasm With High Powdery Mildew Resistance And Quality,and Study On Its Molecular Cytolgenetics

As in most other crops, the genetic variation of cultivated wheat has been eroded under modem agricultural system. Narrow genetic background not only makes wheat increasingly vulnerable to biotic and abiotic stress, but also limits the further improvement of yield and quality. A large of genetic variation in the wild relatives of common wheat are useful resources for wheat improvement. D.villosutn (2n=14,VV), a wild related species of wheat, possesses attractive traits, such as high resistance to powdery mildew, abundant tiller, dough tolerance, high protein content. S.cereale (2n=14,RR), another important alien gene donor, possesses many useful characteristics including resistance to several wheat diseases and tolerance to adverse environment, as well as high yield porential controlled IRS. I R/l B translocation lines as important resistant parents have been used in wheat breeding successfully. In spite of their resistance loss, wheat breeders still think highly of IR/IB lines for their contribution to variety yield and stability. Using many molecular cytobiological techniques and genetic methods, The aim of this study was to search for the preliminary theory of a new method to transfer alien gene and the possibility of direct genetic transfer of genes from D. villosum to wheat using ph lb mutant, as well as the development, identification and cytogenetic characteristics of a trigeneric hybrid germplasm with useful genes from Tavestivum, D.villosum and S.cereale. Results are shown as follows: 1. The miotic root-tip cells of rye (S. cereale L.) and D. villosum were treated under different combinations of Brdu solution concentrations and times for culture. Results indicated that chromosomal fragile sites were observed in 9.3% cells of rye and appeared on four locations of three rye chromosomes, with 1.4%, 2.1%, 4.3% and 5.9% respectively, only afler vigor root-tip cells were treated with Brdu (5OugIml) for 20-21 h, but were not on D. villosum chromosomes under any treatment. This result not only showed that there were fragile sites on plant chromosomes, but also suggested that expresstion of fragile sites on many rye chromosomes could be related to complicated chromosomes translocation in the evolution of rye, and alien gene transfer through reak-reunion?could be induced by the expression of chromosome fragile sites. 2. Meiotic chromosome pairing analysis revealed that the average chromosome 92 configuration were 2n~2813.55 I +5.95 II +0.55111+0.22 IV (Xta=9.72) and 2n2826 I +111 (Xta0.48) in CSphIbXD.villosum and CSph X D.villosum F1 hybrids respectively,indicating that homoeologous chromosome pairing increasing dramatically in PMCs of F1 hybrid involving ph lb. Meiotic GISH analysis of Fl hybrids with phlb gene further detected three types of chromosome pairing with different frequencies, that is, 0.98 W-D, 0.11 W-W-D and 0.02 D-W-D, showing that phlb greatly promoted homoeologous chromosome pairing between wheat and D.villosum, but more dramatically between wheat genomes. P1db or Phlb-like gene didn't existed in D.villosum, 3. Many abnormal meiotic phenomena were observed during microsprorogenesis of F1 hybrid of wheat and D. villosum. F1 hybrids were self-sterile seriously. Decreased backcross seed set of F1 hybrid with phlb, only 0.61%, was due to phlb interfering the meiotic restitution division compared to 6.67% of F1 hybrid without phlb,. Although the backcross...