Studies On Blast Resistance Of Indica Hybrid Rice And Backbone Parents

Rice blast is one of the most important diseases that threaten the safety of rice production.Cultivating resistant varieties is the most economical and efficient way to control the damage of rice blast.In this study,the resistance of rice materials(73 rice restorer lines,15 rice male sterile lines and 145 rice hybrid combinations)were evaluated by the method of natural induction of rice blast in the field.At the same time,the blast resistance genes of the tested materials were detected by using the molecular markers of 10 major genes(Pi2,Pizt,Pi9,Pikh,Pikm,Pid3,Pib,Pit,Pi5 and Pita)to understand the distribution of resistance genes.To analyze the application value of these major resistance genes in rice breeding is of great significance for rice blast resistance breeding and enrich genotype database of rice varieties resistant to rice blast.The main results are as follows:1)Among the 10 blast resistance genes detected,Pita is the most widely distributed resistance gene in rice varieties,accounting for more than 34.00% of the three rice lines.The distribution frequencies of Pi2,Pizt,Pikh,Pikm,Pid3 and Pi5 in rice male sterile lines were 6.67%,6.67%,20.00%,13.33%,6.67% and 6.67%,respectively,while Pit,Pib and Pi9 resistance genes were not found in 15 rice male sterile lines.Except for the low distribution frequency of Pi54,Pikm and Pi9 in rice restorer lines(conventional rice),the other 7 resistance genes were widely distributed in rice restorer lines(conventional rice).Pib,Pi54,Pi5 and Pikm were highly distributed in rice hybrid combinations,which were45.52%,38.62%,51.72% and 17.24%,respectively.Other resistance genes such as Pi2,Pizt,Pid3 and Pit were rarely found in rice hybrid materials,and Pi9 gene was not detected in any rice hybrid combination.2)The resistance of 233 rice materials was identified in the rice blast nursery of Daweishan Town,Liuyang City.When the rice materials carried 0-3 blast resistance genes,the average comprehensive resistance grades were 4.62,3.25,3.04 and 3.49 respectively,and the difference was not significant,but showed an overall downward trend.However,those carrying 4 blast resistance genes(average comprehensive resistance grade 1.84)were significantly lower than those carrying 3 resistance genes and less than 4 genes carrying 5rice blast resistance genes(average comprehensive resistance grade 0.67).The average comprehensive resistance grade of materials carrying 6 or more than 6 was 0 grade.On the whole,the average comprehensive resistance grade decreased with the increase of the number of resistance genes,that is,the resistance to rice blast increased with the increase of the number of resistance genes.