DIFFERENT RICE BLAST RESISTANCE GENES CONTRIBUTING TO THE BROAD-SPECTRUM RESISTANCE IN ELITE MALE STERILE AND RESTORER LINES FOR HYBRID RICE BREEDING

Abstract

Rice blast is one of the most destructive diseases of rice worldwide. Three-line hybrid rice provides a high efficacy system to exploit heterosis that contributes to the yield increase in the past decades. A disease-resistant breeding program has released two elite male sterile lines, Gang-Xiang 1A (GX1A) and D-Xiang 4A (DX4A), and an elite restorer line, Shuhui 707 (SH707), which showed resistance to 102 isolates of Magnaporthe oryzae. To address the question whether the sterile lines and the restorer line contained different resistance genes, expression levels of the functionally cloned blast resistance genes were examined by real-time PCR (RT-PCR). Our data demonstrated that Pikm, Pia, Pid2, Pi-ta, and Pi5 were the candidate contributors of resistance in GX1A, DX4A and/or SH707, because of their high expression. Resistant spectrum assay and sequence polymorphism analysis narrowed down the potentially resistant contributors to Pikm and Pid2 in GX1A and DX4A, and Pi-ta, Pi5 and Pid2 in SH707, respectively. These data indicate that the male sterile lines and the restorer line possess different resistance genes and are highly valuable in disease-resistant breeding programs for developing new male sterile and restorer lines. Therefore, hybrid rice has the advantage to pyramid multiple disease resistance genes by introduction of different resistance genes into the parental male sterile lines and restorer lines.