Introgresion of the SH3 gene resistant to rust (Hemileia vastatrix) in improved lines of CASTILLO variety (Coffea arabica L.)

The genetic improvement at Cenicafe has developed varieties with resistance to Coffee Leaf Rust (CLR) (Hemileia vastatrix) derived from the Timor Hybrid. These varieties have durable rust resistance, especially against race II, the predominant race. In Colombia, these varieties have been cultivated for three decades and still show resistance. Recently, new rust races have appeared attacking these varieties. Consequently incorporation of different resistance genes into new varieties is being sought. The present study aims to determine the presence of the SH3 resistance gene using the SCAR marker BA-124-12K-f and to evaluate its effect in F1 and F2 progenies derived from crosses of 4 lines of the Castillo® variety (C. arabica) with the varieties S288/23 and BA-2 introgressed with the SH3 gene. Eight F1 populations were inoculated using the detached leaf method and evaluated by the incubation and the latency periods (IP and LP). Plants 9 months old from the F2 populations were inoculated in the greenhouse and compared for sporulation presence. All F1 and F2 populations whose progenitor contained the SH3 gene-marker were resistant. However, rust resistant plants that did not present the band in the F2 progenies derived from BA-2 progenitor also had the rust resistance SH2 gene and, some plants derived from S.288 progenitor, in addition to the SH3 gene, also had the SH1 gene. The resistant F2 plants were planted in the field to be evaluated for agronomic traits and to continue the breeding process. The best progenies will be the basis future varieties aimed for durable resistance to CLR. Key words: Coffea arabica, Hemileia vastatrix, Coffea liberica, SH3 gene, marker assisted selection.