Effects of pollination with different apple cultivars’ pollen on postharvest disease resistance of apple fruits to apple ring rot disease

Objectives This study investigated the influence of xenia on disease resistance in apple fruits, with a specific focus on the impact of resistant pollen on the susceptibility of hybrid fruits to apple ring rot, a major threat to the apple industry in China. Materials and Methods Hybrid fruits were produced by pollinating susceptible apple cultivars with both resistant and susceptible pollen. Disease resistance was assessed through inoculation with the ring rot pathogen and subsequent evaluation of disease incidence, latent period, and lesion development. The expression of candidate mobile mRNAs associated with disease resistance was analyzed using quantitative reverse transcription polymerase chain reaction (qRT-RCR). Results The application of resistant pollen significantly reduced disease incidence (by up to 90% in the ‘Fuji’ × ‘Jiguan’ combination) and lesion development in hybrid fruits compared with those pollinated with susceptible cultivars. Fruits pollinated with resistant cultivars also exhibited longer latent periods and smaller lesions, with a 60%–86% reduction in lesion incidence observed between resistant and susceptible combinations. Two mobile mRNAs, MdRGA3 and MdMYC2, were identified as key signaling molecules, whose expression is significantly upregulated during late fruit maturation stages, suggesting their involvement in enhancing disease resistance. Conclusions The findings demonstrate that xenia can effectively improve disease resistance in apple fruits, highlighting its potential to enhance both fruit quality and resilience against diseases like apple ring rot. This research contributes valuable insights into the molecular mechanisms underlying xenia and supports the development of sustainable practices in apple cultivation.