| Rice is one of the most important staple food crops in the world. Rice blast,caused by the fungal pathegon of Magnaporthe oryzae, is a main disease in rice production, which can cause 10%～30% of yield loss in epidemic years. Development and application of resistant rice varieties harboring broad-spectrum blast resistance gene(s) is the most effective, economical and environment-friendly strategy to control the damage of this disease. Therefore, we need to foster a broad spectrum, stable and durable blast resistance varieties. This research according to the broad spectrum of durable blast resistance genes Pi9 introns sequence design DNA marker Ins2-1, through marker-assisted selection and continuous backcross breeding, improving the blast resistance of 21 indica rice lines. The main results are as follows:1. Through reviewing ten Magnaporthe oryzae strains preserved in our laboratory, the growth of mycelium and sporulation ability of the strains in tomato-oat medium was investigated. Among them:three were well-preserved, seven have been pollution, and after the purification they are pollution-free, among fifty-one tested races or strains, two showed excellent sporulation ability, five showed poor sporulation ability, and three couldn’t produce spores at all. Observe the kind of hypha color found that KOH hyphae is black, the 195-2-2, X2007A-7 hypha is white, the rest of the hyphae of seven strains are dark grey black. Through cultivation of 10 rice blast fungus strains, it is known that the rice blast fungus strains in tomato-oat culture medium on the growth cycle of about 20 d.2. CO39,21 rice receptors and 75-1-127, the donor of the Pi9 gene was investigated byphenotypic analyses of 25 Magnaporthe oryzae races or strains. Blast resistance investigation in field nursery and the results shows that all receptors expressed different grades of susceptibility, t implied that blast resistance of all tested receptor rice lines is needed to be improved. In addition, the resistant spectrum showed that these parents may contain antibacterial spectrum and Pi9 complementary new rice blast resistance genes, improved through backcross these receptors, resistance to rice blast of the parents may be able to get resistance spectrum than Pi9 donor parent 75-1-127 more widely, also stronger varieties resistance.3. Ins2-1, a dominant functional DNA marker, was developed based on the intron sequence of the broad-spectrum blast resistance gene Pi9, showed stable polymorphism between 21 receptor parents and 75-1-127, the Pi9 donor. And the selection efficiency of the marker genotype for blast resistance phenotype was 100%. In tai wai, induction of natural disease nursery were used for all the material for the disease, after using molecular markers of Fengyuan B develop Ins2-1×75-1-127 and E32×75-1-127 BC6F1 group random sampling of genotype identification of plant, to detect efficiency of molecular marker assisted selection, the results show that Ins2-1 marker genotype phenotype selection efficiency was 100%, the resistance to rice blast proof this tag can be used in MAS breeding practice as the basis of choice.4. Above molecular marker was employed for marker-assisted selection in consecutive backcross breeding to improve blast resistance of the tested receptor rice lines, and five BC6F3 population, five BC6F2 populations, three BC6F1 populations and seven other populations were developed, which paved a good foundation for further breeding elite blast resistant rice varieties.5. To improve blast resistance of the early season indica rice line 1701, Ins2-1 was used for MAS breeding. BC6F2 population, harboring the Pi9 gene and possessing receptor’s genomic background, was developed by consecutive backcrossing and bagged-pollination, and a blast resistant rice pure line, named resistant 1701, was identified from the BC6F3 families by genotypic and phenotypic analyses, these work paved a way for breeding elite blast resistant rice varieties or hybrids. |
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