Establishment of a broad-spectrum marker for er1/PsMLO1 powdery mildew resistance in pea (Pisum sativum L.)

O oídio, causado pelo fungo ascomycete Erysiphe pisi Syd, é uma das doenças mais importantes que afectam a produção de ervilha (Pisum sativum L.) em Portugal e em países por todo o mundo (Sousa, 1999). Esta doença prospera em climas húmidos temperados causando perdas até 50% nas colheitas de ervilha, uma leguminosa muito importante e vastamente cultivada na Europa, sendo a quarta mais cultivada em todo o mundo (Rubiales et al., 2009; Warkentin et al., 1996).Powdery mildew caused by the biotrophic ascomycete fungus Erysiphe pisi Syd. is one the most devastating diseases of (Pisum sativum L.) with a considerable impact in seed production. So far, the most efficient genetic resistance to this disease identified is conferred by the naturally occurring or experimentally induced by chemical mutagenesis recessive state of the locus er1. Identified over 6 decades ago and genetically mapped to the Pisum sativum Linkage Group VI over 20 years ago, this gene was recently identified as a homolog of the barley (Hordeum sativum L.) powdery mildew resistance gene MLO, and renamed as PsMLO1. The broad spectrum resistance conferred by the er1/PsMLO1 locus was found to be a consequence of the loss of function of the encoded PsMLO1 protein. After the publication of the expressed sequence of this gene by another research group, we published the genomic sequence of this gene, which harbors a relatively long (TA) microsatellite sequence (SSR) in the fifth intron. SSR markers based on this highly polymorphic microsatellite can be used for marker-assisted selection in multiple pea powdery mildew resistance breeding programs involving the er1/ PsMLO1 resistance, except in the rare circumstances where the progenitor lines are monomorphic for the microsatellite sequence. The use of established SSR markers is an affordable and straightforward approach for identification and discrimination of alleles of progenitors in breeding programs, permiting the easy analysis of their inheritance among progenie