Identification of a major QTL for adult plant resistance to coffee leaf rust (Hemileia vastatrix) in the natural Timor hybrid (Coffea arabica x C. canephora)
Résumé
Most of the commercial varieties of coffee (Coffea arabica L.) derived
from the Timor hybrid (TH) have been shown to contain major genes
for coffee leaf rust (CLR) resistance. To identify markers tightly linked
to such genes, an F2 mapping population derived from a cross between
‘Caturra’ (susceptible variety) and the TH-derived DI.200 line (highly
resistant) was generated. Using expressed sequence information and a
bioinformatics approach, both targeted region amplified polymorphism
(TRAPs) markers and simple sequence repeat (SSR) markers were
identified. Phenotypic evaluations in the field and under controlled conditions confirmed the existence of one quantitative trait locus for CLR
resistance. Four candidate SSR markers were associated with high
CLR resistance. They spanning a region of 2.5 cM designated QCLR_4
located within chromosome 4 of the international C. canephora map.
The presence of this region was confirmed in a set of elite lines and
commercial varieties. The QCLR_4 region corresponds to a new and
genetically independent SH locus that could potentially be useful in
gene pyramiding with other genes to enhance rust resistance in TH
derivatives.