Peach cultivar ‘DaHongPao’: a promising resource for gummosis disease resistance from laboratory and field investigations

Gummosis, a severe fungal disease affecting peach production worldwide, poses a significant threat to peach orchards. Despite the fact that peach originates from China with rich peach germplasm resources, the identification of tolerant or resistant resources to gummosis remains elusive. Previously, the evaluation of resistance to peach gummosis disease relied on field investigation. In this study, we evaluated the resistance from twelve peach genetic resources against gummosis both under laboratory and field conditions, by inoculating detached current-year shoots with the causal pathogen Lasiodiplodia theobromae. Based on lesion length under laboratory conditions, the tested resources were divided into three levels: high tolerance [exemplified by DaHongPao (DHP) and HuangJinMi (HJM)], high susceptibility (evident in ChunYuHuangTao, CYHT), mid-susceptibility (the others). Field investigation validated DHP and HJM as tolerant genotypes, while CYHT exhibited high susceptibility. Correlation analysis revealed a strong correlation (R = 0.8663) between field gummosis grades and lesion length, but not with gum formation ratio (R = 0.2718). Furthermore, lenticel density was negatively correlated with the severity of gummosis in peach orchards (R = 0.8786). Additionally, the relative fungal biomass in infected DHP shoots was significantly lower than that in CYHT shoots. DHP also showed elevated levels of ROS and reduced activities of POD upon L. theobromae infection compared with CYHT. Moreover, DHP exhibited higher transcript levels of defense-related genes. Altogether, this study establishes an in vitro evaluation method for peach gummosis and using this method we preliminarily identify DHP as a potential tolerant genotype, offering prospects for peach gummosis control and breeding efforts.