Selecting The Pyramids Of Blast Resistance Genes In Ningxia Rice Assisted By Molecular Marker

Rice blast is one of the most serious diseases affecting rice production.Scientific research and practical production experience show that breeding resistant varieties is the most economical and effective means to prevent rice blast outbreak.Blast resistance gene polymerization is one of the methods to cultivate varieties with broad-spectrum and long-term resistance.Therefore,in this study,582 rice hybrids were used as the experimental materials,and the resistance to blast will be identified using dominant physiological races of rice blast pathogen in Ningxia through the method of artificial inoculation and natural induction.At the same time,molecular detection of blast resistance gene was carried out by using functional markers of cloned blast resistance genes pita.pib,pikm,pi9,pi2,pi5,pikh and pid2.Then the agronomic characters of the antagonistic materials were examined.Finally,Comprehensive analysis was carried out from three aspects of disease resistance,blast resistance genotype and agronomic characters.The aim of this study was to select a genetic polymer with high resistance to blast and good agronomic characters,and provided theoretical basis and breeding materials for rice blast resistance breeding in Ningxia.The main results are summarized as follows:(1)Among the tested materials,18420-10,18455-5,18455-6,18455-7,18455-8,18455-9 and 18455-10 showed high resistance to rice blast and could be used as intermediate materials for blast resistance breeding.18418-1 and 18421-1 were highly sensitive materials,and other agronomic traits are also not prominent,so they should be eliminated directly.18447-3 was also a highly susceptible material,but it's agronomic traits,especially its yield,were prominent,which could be used as an alternative material for studying the linkage between agronomic traits and blast resistance.The resistance and genotype of genes polymer 18463-10 were both excellent,which could be used as the key material for the breeding of blast resistant rice in Ningxia region.(2)Through genotype analysis,it was found that in the genetic polymerization breeding of rice blast resistance in Ningxia region,the combination of genes with outstanding resistance to rice blast were(pita+pib+pikm+pi5+pikh),(pita+pid2),(pita+pi2),(pita+pib+pi9-pi2-pikh)and(pita+pikm+pi2+pikh+pid2).At the same time,some genotype combinations with obvious negative effects were suggested to be carefully considered in the polymerization breeding of rice blast resistance in Ningxia region.They were(pita+pib+pi9+pi5+pikh),(pita+pikm+pib+pid2),(pita+pi5+pikh),(pita+pikm+pi9+pi2+pid2)and(pita+pi5+pid2).(3)Through the comprehensive analysis of disease resistance,blast resistance genotype and agronomic characters,it was found that the resistance level did not increase with the increase of the number of genes when the rice blast resistance genes were polymerized.Rather,different genes exhibit complex interactions.At the same time,under the influence of bad linkage genes,the more the resistance genes polymerized,the more the adverse interference to the agronomic traits.Therefore,the selection of genes for rice blast resistance gene polymerization breeding should include two aspects:gene effect and gene quantity.