Marker-Assisted Introgression of Quantitative Resistance Gene pi21 Confers Broad Spectrum Resistance to Rice Blast

摘要

The quantitative resistance genepi21from Sensho was introgressed to anindicabreeding line IR63307-4B-13-2, a pyramiding line IRBB4/5/13/21, and a tropicaljaponicaline Kinandang Patong by marker-assisted backcrossing. A total of 192 improved lines at the BC4F3and BC4F4generations were developed and confirmed to have the gene introgression via genotyping using api21-specific InDel marker. Thirteen randomly selected improved lines, representing all the three genetic backgrounds, demonstrated resistance against leaf blast composites in the field and a broader spectrum resistance against individual isolates compared to the recurrent parents in the glasshouse. Specifically, the tested lines exhibitedpi21-acquired resistance against 11 leaf blast isolates that elicited susceptible reactions from the recurrent parents. All the tested lines maintained a comparative heading date, and similar or improved panicle length, number of primary branches per panicle and number of total grains per panicle relative to the recurrent parents. The physical grain characteristics of the recurrent parents were also maintained in the 13 lines tested, although variability in the amylose content and chalkiness degree was observed. The successful marker-assisted introgression ofpi21in diverse genetic backgrounds and the resulting broader spectrum resistance of improved lines against leaf blast indicate the potential ofpi21for deployment in cultivars grown across other rice growing regions in Asia.