Comparative metabolomic analysis of resistant and susceptible Actinidia rufa and Actinidia chinensis var.chinensis hybrid germplasms in re-sponse to Pseudomonas syringae pv.actinidiae infection

HE Di; ZHU Jiahui; PAN Hui; LI Wenyi; YANG Jie; HUANG Yue; ZHONG Caihong; LIU Pu; LI Li

doi:10.13925/j.cnki.gsxb.20250267

Abstract：[Objective]Actinidia Lindl.,a deciduous perennial liana genus endemic to China,is recog-nized globally as a functional fruit crop owing to its unique organoleptic characteristics,exceptional nu-tritional profile(notably distinguished as the ascorbate hyperaccumulator within Rosidae clade),and pharmacological properties.The Chinese kiwifruit industry has undergone remarkable expansion,with cultivation areas reaching 300 000 hectares and annual production achieving 4.346 million metric tons by 2024.This growth has significantly contributed to regional economic development,poverty allevia-tion initiatives,and agroecosystem rehabilitation.Pseudomonas syringae pv.actinidiae(Psa),a phyto-pathogen with rapid dissemination capacity and high virulence,poses severe threats to global kiwifruit production,causing epidemic canker outbreaks.Identifying excellent disease-resistant germplasms,elu-cidating the underlying mechanisms of resistance formation,and developing resistant cultivars are cru-cial approaches to addressing the occurrence of canker.Plant metabolite alterations provide insights in-to metabolic states,gene expression,and protein function.By conducting metabolomics research on the resistant genotype E2545 and susceptible genotype E674 at different infection time points,we can identify differential metabolites,determine associated metabolic pathways,and reveal their roles in bio-logical processes.This study offers a metabolic perspective on the molecular mechanisms underlying the response of kiwifruit materials with differential resistance to Psa infection.[Methods]Invitro stem inoculation assays were conducted on Psa-resistant(E2545)and susceptible(E674)kiwifruit gen-otypes under controlled phytosanitary conditions.Longitudinal sections(1 cm)of xylem-differentiated tissues were sampled proximal and distal from the inoculation site at defined intervals(0,3,7,and 14 days post-inoculation,dpi).Untargeted metabolomic profiling was performed using the ultra-high-per-formance liquid chromatography coupled with quadrupole time-of-flight tandem mass spectrometry(UHPLC-QTOF-MS/MS).Raw metabolite data was acquired using MassLynx V4.2.Data processing including peak extraction and alignment was performed using Progenesis QI.Metabolite identification was achieved against a self-built database(BMK)using MS/MS data,with quantification via multiple reaction monitoring on a triple quadrupole mass spectrometer.Differential metabolites were screened using thresholds of variable importance in projection(VIP)≥1,P-value＜0.05,and log2|FC|≥1.[Re-sults]Comparative metabolomic profiling revealed distinct clustering of specialized metabolites be-tween P.syringae pv.actinidiae(Psa)-resistant and susceptible Actinidia genotypes.Differential metab-olites were predominantly categorized as benzene and substituted derivatives,coumarins and deriva-tives,prenol lipids,carboxylic acids and derivatives.Quantitative analysis demonstrated significant ac-cumulation of 87 defense-related metabolites in resistant germplasm,including key phytoalexins and signaling molecules linked to systemic acquired resistance.Four metabolites exhibiting dual antimicro-bial and immune-priming activities were prioritized:aspirin,liquoric acid,pestalactam B,and valtra-tum.KEGG pathway enrichment analysis revealed significant activation of phenylpropanoid biosynthe-sis and phenylpropanoid metabolism,indicating their critical roles in kiwifruit defense against Psa in-fection.[Conclusion]This study conducted comparative metabolomic profiling of resistant and suscep-tible germplasms in Actinidia rufa and Actinidia chinensis var.chinensis subjected to varying P.syrin-gae pv.actinidiae(Psa)infection periods.Building on these findings,further in-depth research on the key differential metabolites between resistant and susceptible kiwifruit germplasms could elucidate the disease resistance mechanisms of germplasms,providing a theoretical basis for screening novel kiwi-fruit germplasms resistant to bacterial canker.Additionally,antimicrobial activity assays and field trials should be conducted to validate the antibacterial properties of these metabolites,facilitating the devel-opment of innovative biocontrol agents.This integrated approach would advance both the theoretical framework and practical applications in kiwifruit disease resistance breeding and sustainable disease management.