Characterization of Lr75: a partial, broad-spectrum leaf rust resistance gene in wheat
Singla J, Luethi L, Wicker T, Bansal U, Krattinger SG and Keller B (2017) Characterization of Lr75: a partial, broad-spectrum leaf rust resistance gene.Theoretical and Applied Genetics 130: 1-12.
Leaf rust caused by the fungal pathogen Puccinia triticina is a damaging disease of wheat (Triticum aestivum
L.). The combination of several, additively-acting partial disease
resistance genes has been proposed as a suitable strategy to breed wheat
cultivars with high levels of durable field resistance. The Swiss
winter wheat cultivar ‘Forno’ continues to show near-immunity to leaf
rust since its release in the 1980s. This resistance is conferred by the
presence of at least six quantitative trait loci (QTL), one of which is
associated with the morphological trait leaf tip necrosis. Here, we
used a marker-informed strategy to introgress two ‘Forno’ QTLs into the
leaf rust-susceptible Swiss winter wheat cultivar ‘Arina’. The resulting
backcross line ‘ArinaLrFor’ showed markedly increased leaf rust resistance in multiple locations over several years. One of the introgressed QTLs, QLr.sfr-1BS,
is located on chromosome 1BS. We developed chromosome 1B-specific
microsatellite markers by exploiting the Illumina survey sequences of
wheat cv. ‘Chinese Spring’ and mapped QLr.sfr-1BS to a 4.3 cM interval flanked by the SSR markers gwm604 and swm271. QLr.sfr-1BS does not share a genetic location with any of the described leaf rust resistance genes present on chromosome 1B. Therefore, QLr.sfr-1BS is novel and was designated as Lr75.
We conclude that marker-assisted combination of partial resistance
genes is a feasible strategy to increase broad-spectrum leaf rust
resistance. The identification of Lr75 adds a novel and highly useful gene to the small set of known partial, adult plant leaf rust resistance genes.