Selecting with markers linked to the PPVres major QTL is not sufficient to predict resistance to Plum Pox Virus (PPV) in apricot
Publication Overview
Abstract Sharka is one of the most serious viral diseases
affecting stone fruit species and, in apricot, resistance to its
viral agent, the Plum Pox Virus (PPV), is conferred by one
major quantitative trait locus (QTL), named PPVres for PPV
resistance. Previous studies indicated that PPV-resistant cultivars
and breeding progenies can be selected by using a set of
SSR markers (named PGS) targeting the PPVres locus.
However, before these markers can be employed for markerassisted
selection, they were validated in a wide range of
genetic backgrounds and environments. We used a total of
11 mapping populations issued from three distinct environments
to confirm that this marker set located within the QTL
adequately predicted PPV resistance. In this study, we show
that selection of PPV-resistant material based only on markers
co-localizing with the PPVres major locus is not fully reliable.
Indeed, genotype-phenotype discrepancies were observed depending
on the progeny and the PPV-resistant/susceptible
parents. While most of the PPV-resistant individuals displayed
the resistant alleles, a significant number of PPV-susceptible
individuals showed the same resistant haplotype. An effect of
the PPV strain used for phenotyping was also demonstrated.
We thus hypothesize that the presence of other factors or genes
involved in the mechanism of resistance to sharka in apricot
could explain these unexpected results. Our work indicates
that the current PGS marker set is not broadly applicable for
MAS and that marker-assisted breeding based on the sole
PPVres locus is not sufficient to unambiguously select PPVresistant
apricot cultivars.
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