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
