Haplotype-resolved genome assembly provides insights into the genetic basis of green peach aphid resistance in peach.

Abstract

Green peach aphid (GPA) is one of the most destructive pests of peach, threatening both growth and fruit quality. However, the mechanism underlying GPA resistance remains unclear. Here, we performed haplotype-resolved genome assembly of a GPA-resistant cultivar and identified an allele-specific expressed gene, PpNLR1, responsible for the GPA-resistant trait. A genome-wide association study (GWAS) revealed a functional 20-bp insertion or deletion (indel) in the PpNLR1 promoter, which co-segregated with the GPA-resistant trait and directly influenced promoter activity. Furthermore, jasmonate (JA) signaling, activated during GPA infestation, induced the transcription of PpERF109. This transcription factor specifically bound to the "CAAGT" motif within the GWAS-identified 20-bp insertion of the PpNLR1 promoter, resulting in allele-specific expression (ASE). Functional validation of the two alleles (PpNLR1-Hap1 and PpNLR1-Hap2) in both peach and Arabidopsis demonstrated their role in aphid resistance. Additionally, two GPA salivary proteins were identified as effectors, triggering reactive oxygen species (ROS) and activating the peach immune system in conjunction with the PpNLR1 protein. Comparative genomics and phylogenetic analysis indicated that an ∼53.6-kb genomic variation surrounding PpNLR1 underwent negative selection during peach evolution. In conclusion, the JA-mediated PpERF109-PpNLR1 module and GPA effector proteins significantly contribute to GPA resistance in peach. The novel haplotype-resolved genome assembly and identified key genes provide valuable resources for future genomic research and GPA resistance breeding in peach.