Modern elite rice varieties of the 'Green Revolution' have retained a large introgression from wild rice around the Pi33 rice blast resistance locus.
During the breeding process of cultivated crops, resistance genes to pests and diseases are commonly introgressed from wild species. The size of these introgressions is predicted by theoretical models but has rarely been measured in cultivated varieties. By combining resistance tests with isogenic strains, genotyping and sequencing of different rice accessions, it was shown that, in the elite rice variety IR64, the resistance conferring allele of the rice blast resistance gene Pi33 was introgressed from the wild rice Oryza rufipogon (accession IRGC101508). Further characterization of this introgression revealed a large introgression at this locus in IR64 and the related variety IR36. The introgressed fragment represents approximately half of the short arm of rice chromosome 8. This is the first report of a large introgression in a cultivated variety of rice. Such a large introgression is likely to have been maintained during backcrossing only if a selection pressure was exerted on this genomic region. The possible traits that were selected are discussed.
Ballini
Elsa
E
UMR BGPI, AGRO.M-CIRAD-INRA, Montpellier, France.
Berruyer
Romain
R
UMR BGPI, AGRO.M-CIRAD-INRA, Montpellier, France.
Morel
Jean-Benoît
JB
UMR BGPI, AGRO.M-CIRAD-INRA, Montpellier, France.
Lebrun
Marc-Henri
MH
UMR 2847 CNRS-Bayer CropScience, Physiologie des plantes et des champignons lors de l'infection, Lyon, France.
Nottéghem
Jean-Loup
JL
UMR BGPI, AGRO.M-CIRAD-INRA, Montpellier, France.
Tharreau
Didier
D
UMR BGPI, AGRO.M-CIRAD-INRA, Montpellier, France.
D002874:Chromosome Mapping; D018506:Gene Expression Regulation, Plant; D017343:Genes, Plant; D020022:Genetic Predisposition to Disease; D005838:Genotype; D012275:Oryza / Q000235:genetics*; D010802:Phylogeny; D010935:Plant Diseases / Q000235:genetics*