Location: Plant Science ResearchTitle: QTLs for resistance to the leaf rust Puccinia brachypodii in the model grass Brachypodium distachyon Author
Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 7/15/2011
Publication Date: 10/19/2011
Citation: Barbieri, M., Marcel, T.C., Niks, R.E., Francia, E., Pasquariello, M., Mazzamurro, V., Garvin, D.F., Pecchioni, N. 2011. QTLs for resistance to the leaf rust Puccinia brachypodii in the model grass Brachypodium distachyon [abstract]. 1st European Brachypodium Workshop, October 19-21, 2011, Versailles, France. p. 70. Interpretive Summary:
Technical Abstract: The wild grass Brachypodium distachyon is a useful new model for temperate cereals, but its potential to study the interactions with pathogens remains underexploited. Leaf rust is one of the major fungal diseases affecting cereals, and recently the host status of Brachypodium to Puccinia rusts was investigated. We aimed to identify genomic regions associated with quantitative resistance to leaf rust in Brachypodium. Two inbred lines, Bd3-1 and Bd1-1, with quantitative differences in resistance to Puccinia brachypodii, were crossed to develop an F2 population of 110 plants that was evaluated for reaction to a P. brachypodii isolate at both seedling and advanced growth stages by means of the AUDPC (Area Under Disease Progress Curve) score. Results from the F2 population were validated in F2-derived F3 families. Disease evaluations showed quantitative and transgressive segregation for leaf rust resistance. We applied AFLP, SNP, and SSR markers to develop a new Brachypodium linkage map of 203 loci spanning 811.8 cM and anchored it to the Brachypodium genome sequence. Three leaf rust resistance QTLs (Rpbq1, Rpbq2, and Rpbq3) were identified on chromosomes 2, 3, and 4, respectively. The resistant alleles of Rpbq1 and Rpbq2 were contributed by the more resistant parent Bd3-1, while for Rpbq3 the resistant allele came from Bd1-1. This study is, to our knowledge, the first quantitative analysis of a trait in Brachypodium. To begin the process of isolating the QTLs, we chose eight candidate genes close to the peaks of Rpbq2 and Rpbq3, based on genome sequence information. The genes were resequenced in the parents of the mapping population, and polymorphisms were identified for mapping efforts. The validation of a gene sequences for a leaf rust resistance QTL will lead to a deeper understanding of mechanisms of quantitative resistance to this and other rust pathogens that infect members of the Triticeae.