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The 25th International Conference on Virus and other graft transmissible diseases of Fruit crops , Amsterdam, Netherlands, 9 - 13 July 2023, pp.1
Introduction
Understanding the mechanism of resistance to pathogens
in fruit trees is arguably one of the most important areas of study. A major
resistance locus, named PPVres and located in the
upper part of Linkage Group 1 (LG1) of apricot, accounted for 70% of the
resistance to plum pox virus. A cluster of genes of the MATH–TRAF family
located in PPVres locus on LG1 could be responsible for the resistance
to PPV, and particularly a 5 nt deletion on a MATH gene has been hypothesized
to result in loss of function and thereby resistance gene silencing in
susceptible accessions (Zuriaga et al., 2013, 2018). This 5 nt deletion has been used as the most reliable
and easy to use in selecting for the resistant apricots (Decroocq et al., 2014; Gürcan et al., 2019). Besides to MATH–TRAF
family, a genome-wide association (GWA) approach in apricot highlighted other
potential resistance loci, and resolved each to a limited set of candidate
genes for further study (Mariette et a., 2016). Here we also
implemented GWA to determine PPV resistance linked loci in LG1.
Materials and Methods
DNA
sequence of 32 apricots, including resistant and susceptible breeding material
were obtained using high-throughput sequencing. Genomic variants within a
region of ∼300 kb spanning PPVres locus, flanking the 5 nt
deletion were determined. Fifteen indel loci were further investigated together
with the 5 nt deletion by segregation analysis. PCR amplification of 800 seedling
of F1 mapping populations were performed for the 16 loci.
Results and Discussion
DNA reads of the 32 apricots produced by high-throughput
sequencing were mapped to the PPVres locus of the reference apricot genome with
minimum 30x coverage. Over 200 genomic variants, including INDELs and SNPs,
linked to the 5 nt deletion were determined by GWA. Among the 15 loci, a 15 nt deletion located at
114 054 nt poison of 300 kb depicted over 95 % co-segregation with the 5 nt
deletion located at the position 118 674. Further, another 12 nt insertion at
the position 266 005 nt exhibited one hundred percent allelic variation with
the 5 nt deletion. As Marrette et al., (2016) reported previously, it is likely
that more loci linked to the PPV resistance. The new PPV resistance linked loci
has potential to be used for marker assisted selection in apricots.