Peach fungal gummosis (PFG), caused by fungal pathogens in the Botryosphaeriaceae family, including Botryosphaeria dothidea, Lasiodiplodia theobromae, and Diplodia seriata. This disease is a major threat to Prunus production worldwide. The initial symptoms often remain latent until trees are exposed to stress, at which point it can lead to substantial yield losses and even tree mortality. Given the lack of curative fungicide options and the difficulty of managing prolonged latent infections, genetic resistance has become a central focus for integrated PFG management strategies. A key breakthrough in this effort was the identification of Botd8, a major resistance locus derived from the almond cultivar ‘Tardy Nonpareil.’ Mapped to linkage group 8, Botd8 confers dominant resistance to B. dothidea and co-segregates with the red leaf locus (Gr). Its resistance effect was validated in multiple environments and under different inoculation methods, including field, trellis, and wound inoculation. Further validation using detached stem and leaf assays confirmed that genotypes homozygous or heterozygous carrying Botd8 exhibited significantly reduced lesion development following inoculations with B. dothidea and D. seriata. However, Botd8 was not effective against L. theobromae, underscoring the need for additional resistance sources. The strong correlation between detached stem assay results and field ratings also demonstrated the utility of these rapid, non-destructive screening tools in breeding programs. To expand resistance options beyond almond-derived sources, a recent study focused on the low-chill peach landrace ‘Okinawa’. A segregating F1 population from ‘Okinawa’ × (‘Flordaguard’ × PI91459) was phenotyped for disease severity and genotyped via Genotyping-by-Sequencing. QTL analysis revealed a novel resistance locus on linkage group 6, distinct from Botd8. This QTL consistently explained 29–41% of the phenotypic variation across two years, suggesting a polygenic basis for resistance in peach. Notably, the Botd8 haplotype was common in high-chill cultivars but absent in low-chill germplasm, positioning ‘Okinawa’ as a valuable resistance source for subtropical breeding efforts. Collectively, these studies establish a comprehensive framework for developing PFG-resistant peach cultivars
