The green peach aphid (GPA), Myzus persicae, is an important pest of the peach crop. Three major dominant resistance genes have already been detected, Rm1 in the Weeping Flower Peach (WFP) clone, Rm2 in the Rubira clone, and Rm3 in the Fen Shouxing clone. In this study, after NGS resequencing of WFP and Rubira, we found that their genomic sequences in the Rm1 and Rm2 region were similar but very different from that of the susceptible reference peach Lovell. We constructed a BAC library for the GPA-resistant WFP and screened four BAC clones to sequence the target region. The new sequence was 61.7 Kb longer than Lovell and was annotated with four different TIR_NBS_LRR genes. Among them, the TNL1 gene was very overexpressed in WFP leaves 24 h after GPA infestation. This gene was also present and expressed in the Rubira clone and had the same sequence as the candidate Rm3 gene, supporting the hypothesis that the three genes share the same origin. In addition, we identified a second TNL, TNL2, located at 35.4 Kb from TNL1 and slightly overexpressed after GPA infestation. Kasp and size molecular markers were designed for use in marker-assisted selection and were validated in a peach segregating population.

Accumulation of anthocyanin pigments is a primary determinant of fruit quality in peach (Prunus persica L. Batsch). The recessive blood-flesh trait (bf), identified in French cultivars was first mapped on chromosome 4. However, the underlying gene is yet to be identified. In this study, the genetic, molecular and transcriptional bases of the bf trait were investigated. Blood-flesh cultivars showed high levels of cyanidin-3-glucoside and cyanidin-3-rutinoside in the fruit mesocarp about 45-60 days after anthesis. Fine mapping coupled to a positional cloning strategy mapped the bf locus to an 80-kb interval on peach linkage group 4. The sequence polymorphism analysis of genes present in this interval allowed the identification of only one candidate gene for bf a deletion of 21-bp in exon 3 of a PSAK-like gene (PSAK:photosystem I subunit K). A specific marker for the deletion was developed and validated in different genetic backgrounds. An expression study of PpPSAK as well as analysis of structural, regulatory and photosynthesis related genes was performed to compare cultivars with blood-flesh (Montarsa) and without blood-flesh (S11332) during fruit development from 60 days after blooming until fruit maturity. Differently expressed of PpPSAK in the flesh of bf fruit was correlated with expression of anthocyanin biosynthesis structural genes. A protein-protein interaction study was performed and is presented with an open discussion on functional pathways in peach.