Polymerization Of Pi9 And Pi49 Loci By Marker Assisted Selection To Improve Blast Resistance Of Dual-purpose Genic Sterile Rice Chuang5S

Rice blast disease,which has a great impact on rice yield and rice quality,is one of the most destructive diseases in the world.It is well known that to breed resistant varieties harbored with resistant genes is the most cost-effective way to control rice blast.In order to improve the resistance to rice blast of the dual-purpose genic sterile rice,Chuang 5S(C5S),the broad-spectrum resistance genes located on the Pi9 locus,which were harbored in the donor parents of 75-1-127(75,Pi9),GuMei 4(GM4,Pigm)and Tianjinyeshengdao(TY,Pi2-1),and gene on the Pik locus which harbored in the parent of Mowanggu(MWG,Pi49),were introgressed into C5 S by successive backcross and molecular marker assisted selection technology.Thus,several monogenic lines,which contain a single rice blast resistance gene with the genetic background of C5 S,were developed.In this study,several improved lines which pyramided two different resistance genes were bred,by crossed the Pi9/Pigm/Pi2-1 monogenic line to the line with Pi49,using the marker assistant selection technology.The resistance to rice blast of the improved lines was evaluated with both the indoor inoculation method and field disease nursery identification method.The main agronomic traits such as height,panicle length,grain number per panicle,primary branch number and stigma exsertion rate were also studied.The main results are as follows:1)The improved lines,which pyramided the rice blast resistance genes located on Pi9 locus(Pi9,Pigm and Pi2-1)and Pik locus(Pi49),were bred by crossed the monogenic lines with Pi9/Pigm/Pi2-1 gene and Pi49 gene.The markers of RM7311,RM7178,RM3330,which were closely linked to the Pi9 locus,and the marker RM224 which is closely linked to the Pi49 locus,were subjected to molecular marker-assisted selection for the objective genes in the breeding schedule.2)The results of field disease nursery identification showed that the disease severity score(DSS)of the recipient parent of Chuang 5S was 7,that of the monogenic lines of C5S-Pi49,C5S-Pigm and C5S-Pi2-1 was 3,and the C5S-Pi9 was 0.Ninety-two of the total ninety-five improved lines which pyramided the Pi9 and Pik locus exhibit the DSS of 0,except other three showed 1.In the laboratory inoculation identification,the DSS of all monogenic lines decreased to various extent compared with the recipient parent 5S,and the difference reached significant level at 0.05 for 4 rice blast strains.The DSS of all improved lines which pyramided the Pi9 and Pik locus was significantly lower than that of Chuang 5S,for all rice blast strains except the strain of 16-572.All lines polymerized two resistance genes showed lower DSS than that of the monogenic line,but there were no significant difference between the polymerized lines and monogenic lines except for C5S-Pi49/Pigm and C5S-Pigm.3)Compared with Chuang 5S,the main agronomic traits of the improved male sterile lines varied to various extent depend on the parental pedigree and specific traits.For example,the plant height,ear length and grain number per panicle of C5S-Pi49/Pi9 lines increased significantly,while those of C5S-Pi49/Pi2-1 lines significantly decreased,but there was no significant change in the above traits for C5S-Pi49/Pigm lines.Usually,the difference among the different pedigree lines derived from the same parental cross was not significant for all the traits.