Dissection Of Mechanisms Underlying The MPIC-mediated Rice Blast Resistance And Locus-related Disease Resistance Molecular Breeding

Rice is a staple crop which has the largest growing area and the highest yield per unit area in China. Secure production of rice connects with our national food security issue. Rice blast is one of the major rice diseases. Due to the increasing expansion in hazard area and level, rice blast has become an important factor in restricting the high and stable yield of rice. To carry out the research on rice blast resistance molecular function and signal transduction pathway is of great significance for rice resistance breeding.This study was carried out on the basis of our previous work. The MPIC gene is a mosaic gene that has the most part of Pi2except for the Pi9’s LRR domain. In this study, we found that MPIC transgenic rice plant has the same blast resistance spectrum as the Pi9transgenic rice plant. Out of expectation, the MPIC plants enhance resistance to virulent race of Xanthomonas oryzae pv. Oryzae(Xoo) and exhibit autoimminity-like phenotypes. Comparing to Pi9, MPIC contains a total of9amino acid differences, which are predicted to cause the activation of autoimmunity. It is therefore intriguing to further identify which amino acid residue(s) control the transition between Pi9and MPIC. In this study, we employed a rice-protoplast-based transient assay system to achieve our research goal. By referring the microarray data, we selected a total of260upregulated genes for further validation using a RT-PCR method. Three genes that were highly induced of their expression in MPIC plants were identified. The promoters of these three genes were cloned and used for generating the luciferase (LUC) fusion vectors. In addition, salicylic acid (SA) deficient MPIC transgenic rice plants were generated by overexpression of either OsSAMT1or bacterial NahG gene.The marker aided selection (MAS) method was emploied to introduce different rice blast resistance genes into an elite male sterial line, Y58S. First, we identified two SSR markers RM7193and RM564that were linked with the P2/9locus and able to distinguish GUMEI-2,75-1-127, Toridel, Zenith, representing Pi25, Pi9, Piz-t, Piz, respectively from Y58S. In F1, BC1F1, BC2F1, BC3F1generations, I used these two SSR markers for screen of resistance genes. Genetic background screen of BC3F1generation was carried out and the line that had the most genetic background as Y58S was selected. The disease resistance of the BC3F1lines was assessed using a set of isolates that are able to differentiate the resistance spectrum of those donor resistance lines from Y58S.