NBS-LRR proteins represent the largest class of R genes in plants, and nearly 500 NBS-LRR genes have been identified in both Nipponbare and

93-11 [31]. Eighteen of 20 cloned blast R genes (except Pid2 and pi21) encode NBS-LRR proteins [21], [26], [35] and [40]. Colocalizations of the NBS-LRR genes and blast resistance loci were identified through DAPT molecular weight genetic analyses [14] and [59]. Therefore, NBS-LRR genes are the most likely potential candidates for further blast R genes [70]. In our study, eight intact NBS-LRR genes in the 274 kb region encompassing Pi60(t) were identified in the Nipponbare sequence, but only six intact NBS-LRR genes were identified in the 93-11 sequence in the Gramene database ( Fig. 1-d), including the two alleles of Pia/PiCO39 (SasRGA4 and SasRGA5). On the other hand, four NBS-LRR genes exist in the 200 kb target region of Pi61(t) in 93-11, and all of them showed differences in comparison with the corresponding NBS-LRR genes in Nipponbare. Therefore, it is difficult to shortlist candidate genes for Pi61(t). We need to further reduce the target interval of Pi61(t), www.selleckchem.com/products/ink128.html or to transform all four NBS-LRR genes into susceptible cultivars for complementation tests. In addition, another blast R gene, Pi41(t), present

in 93-11 was predicted as a NBS-LRR-type gene [47]. Therefore, we postulate that the broad-spectrum blast resistance in 93-11 is mediated by multiple NBS-LRR genes, representing a molecular mechanism of broad-spectrum resistance different

from Digu [77], and Pi2, Pi9 and Piz-t [79]. In summary, the broad-spectrum blast resistant cv. 93-11 harbors at least three R genes, Pi60(t) on chromosome 11, and Pi61(t) and Pi41 on chromosome 12. Pi60(t) and Pi61(t) are both embedded in recombination-suppressed regions with several clustered NBS-LRR genes. We identified Rebamipide two tightly linked flanking markers, K1-4 and E12, and two co-segregating markers, Y10 and B1, for Pi60(t); and two tightly linked flanking markers G8 and M2, and one co-segregating marker M9 for Pi61(t). These markers should ensure rapid and accurate transfer of the two R genes from 93-11 into new breeding lines through MAS. The delineation of physical positions and the short-listed candidate genes of the two blast R loci have set solid foundations for positional cloning of Pi60(t) and Pi61(t). We thank Dr. Yulin Jia, USDA-ARS Dale Bumpers National Rice Research Center, Stuttgart, Arkansas, USA for helpful discussion. This work was supported by grants from the National Natural Science Foundation of China (Grant No. 30871606), the Special Fund for Agro-scientific Research in the Public Interest Program of China (Grant No. 20120314), and the Major Science and Technology Project to Create New Crop Cultivars using Gene Transfer Technology (Grant No. 2011ZX08001-002). “
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