Genetic and physical mapping of the SH3 region that confers resistance to leaf rust in coffee tree (Coffea arabica L.)
Resistance to coffee leaf rust is conferred by SH3, a major dominant gene that has been introgressed from a wild coffee species Coffea liberica (genome L) into the allotetraploid cultivated species, Coffea arabica (genome CaEa). As the first step toward the map-based cloning of the SH3 gene, using a bacterial artificial chromosome (BAC) library, we describe the construction of a physical map in C. arabica spanning the resistance locus. This physical map consists in two homeologous BAC-contigs of 1,170 and 1,208 kb corresponding to the subgenomes Ca and Ea, respectively. Genetic analysis was performed using a single nucleotide polymorphism detection assay based on Sanger sequencing of amplicons. The C. liberica-derived chromosome segment that carries the SH3 resistance gene appeared to be introgressed on the sub-genome Ca. The position of the SH3 locus was delimited within an interval of 550 kb on the physical map. In addition, our results indicated a sixfold reduction in recombination frequency in the introgressed SH3 region compared to the orthologous region in Coffea canephora.
Summary: | Resistance to coffee leaf rust is conferred by SH3, a major dominant gene that has been introgressed from a wild coffee species Coffea liberica (genome L) into the allotetraploid cultivated species, Coffea arabica (genome CaEa). As the first step toward the map-based cloning of the SH3 gene, using a bacterial artificial chromosome (BAC) library, we describe the construction of a physical map in C. arabica spanning the resistance locus. This physical map consists in two homeologous BAC-contigs of 1,170 and 1,208 kb corresponding to the subgenomes Ca and Ea, respectively. Genetic analysis was performed using a single nucleotide polymorphism detection assay based on Sanger sequencing of amplicons. The C. liberica-derived chromosome segment that carries the SH3 resistance gene appeared to be introgressed on the sub-genome Ca. The position of the SH3 locus was delimited within an interval of 550 kb on the physical map. In addition, our results indicated a sixfold reduction in recombination frequency in the introgressed SH3 region compared to the orthologous region in Coffea canephora. |
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