Fine mapping of the Bsrl barley stripe mosaic virus resistance gene in the model grass Brachypodium distachyon.

Authors: CUI, Y - China Agricultural University; LEE, M - University Of California; HUO, N - University Of California; BRAGG, J - University Of California; YAN, L - China Agricultural University; YUAN, C - China Agricultural University; LI, C - China Agricultural University; HOLDITCH, S - University Of California; XIE, J - China Agricultural University; LUO, M - University Of California; LI, D - China Agricultural University; YU, J - China Agricultural University; MARTIN, J - Joint Genome Institute; SCHACKWITZ, W - Joint Genome Institute; Gu, Yong; Vogel, John; JACKSON, A - University Of California; LIU, Z - China Agricultural University; Garvin, David

Submitted to: PLOS ONE
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/4/2012
Publication Date: 6/4/2012
Citation: Cui, Y., Lee, M.Y., Huo, N., Bragg, J., Yan, L., Yuan, C., Li, C., Holditch, S.J., Xie, J., Luo, M.C., Li, D., Yu, J., Martin, J., Schackwitz, W., Gu, Y.Q., Vogel, J.P., Jackson, A.O., Liu, Z., Garvin, D.F. 2012. Fine mapping of the Bsrl barley stripe mosaic virus resistance gene in the model grass Brachypodium distachyon. PLoS One. 7:e38333.

Interpretive Summary: Viruses damage many crops. Barley stripe mosaic virus (BSMV) is one virus that infects barley and can cause significant yield losses. While there are BSMV resistance genes in barley that can provide protection against the virus, none have been isolated. In this study, BSMV resistance was characterized in the model grass Brachypodium distachyon (Brachypodium), a close relative of barley with the same general complement of genes. Genetic studies revealed that the BSMV resistance of one Brachypodium genotype due to a single dominant gene, named Bsr1. Using genetic mapping methods in a Brachypodium population segregating for Bsr1, the location of this gene was narrowed down to a part of one chromosome containing just 5 genes. One of the genes has features similar to some other virus resistance genes that have been isolated in other species, and thus is a strong candidate to be Bsr1. Future research will be directed at confirming the gene’s identity. This study demonstrates the power of Brachypodium for translational research on disease resistance in cool season cereal crops. The isolation of a BSMV resistance gene from Brachypodium will permit functional studies on how the gene provides protection against the virus. Further, inserting the gene into barley may provide a new method for reducing losses from BSMV and thus increasing producer profits.

Technical Abstract: The ND18 strain of Barley stripe mosaic virus (BSMV) infects several lines of Brachypodium distachyon, a recently developed model system for genomics research in cereals. Among the inbred lines tested, Bd3-1 is highly resistant at 20 to 25 °C, whereas Bd21 is susceptible and infection results in an intense mosaic phenotype accompanied by high levels of replicating virus. We generated an F6:7 recombinant inbred line (RIL) population from a cross between Bd3-1 and Bd21 and used the RILs and an F2 population of a second Bd21 X Bd3-1 cross to evaluate the inheritance of resistance. The results indicate that resistance is encoded by a single dominant gene, which we have designated Barley stripe mosaic virus resistance 1 (Bsr1). We constructed a genetic linkage map of the RIL population using SNP markers to map this gene to within 705 Kb of the distal end of the top of chromosome 3. Additional CAPS and Indel markers were used to fine map Bsr1 to a 23 kB interval containing five putative genes. Our study demonstrates the power of using RILs to rapidly map the genetic determinants of BSMV resistance in Brachypodium. Moreover, the RILs and their associated genetic map, when combined with the complete genomic sequence of Brachypodium, provide new resources for genetic analyses of many other traits.