Genome-wide identification of R genes and exploitation of candidate RGA markers in rice

By scanning the whole genomic sequence of japonica rice using 45 known plant disease resistance (R) genes, we identified 2119 resistance gene homologs or ana- logs (RGAs) and verified that RGAs are not randomly dis- tributed but tend to cluster in the rice genome. The RGAs were classified into 21 families according to their functional domain based on Hidden Markov model (HMM). By com- paring the RGAs of japonica rice with the whole genomic sequence of indica rice, we found 702 RGAs allelic between the two subspecies and revealed that 671 (95.6%) of them have length difference (InDels) in their genomic sequences (including coding and non-coding regions) between the two subspecies, suggesting that RGAs are highly polymorphic between the two subspecies in rice. We also exploited 402 PCR-based and co-dominant candidate RGA markers by designing primer pairs on the regions flanking the InDels and validating them via e-PCR. The length differences of the candidate RGA markers between the two subspecies are from 1 to 742 bp, with an average of 10.26 bp. All related information of the RGAs is available from our web site (http://ibi.zju.edu.cn/RGAs/index.html).