Pre-fruit exogenous ATaiLing application controls fruit spot in Rosa roxburghii caused by Diaporthe cercidis and improves fruit quality

Fruit spot, a newly identified fungal disease, has emerged in the major production areas of Rosa roxburghii in Guizhou Province, significantly reducing both fruit yield and quality. Based on pathogenicity, morphology, and multigene phylogenetic analysis, the causative agent of this disease was identified as Diaporthe cercidis strain LX13—the first report of this pathogen infecting R. roxburghii. Optimal growth conditions for D. cercidis LX13 on PDA medium were determined to be 28 °C, pH 7.0, full light, with glucose, peptone and yeast extract identified as favorable nutrient sources. In vitro mycelial growth inhibition assays revealed that four plant immunity inducers, ATaiLing (ATL), VDAL, Pulvtong and ProAct, exhibited limited direct antimicrobial activity (<50 %) against D. cercidis LX13. Among them, ATL (active ingredients: 3 % amino-oligosaccharides and 3 % PeaT1 protein) showed the strongest antifungal effect (20.05 %–49.02 %), significantly outperforming the other inducers (2.58 %–18.96 %). Field trials demonstrated ATL efficacy in controlling fruit spot in R. roxburghii. Its induced resistance peaked at 14 days after the third spray (91.54 % control efficacy), then gradually declined to its lowest level at 35 days (68.30 % control efficacy). Additionally, ATL enhanced fruit quality by elevating disease-resistance compounds (soluble sugars, proteins, lignin, flavonoids, and total phenols) and boosting antioxidant activity at maturity. This study provides the first evidence of D. cercidis LX13 as the causal agent of R. roxburghii fruit spot disease and highlights ATL as an eco-friendly plant immunity inducer for sustainable disease management, offering both theoretical insights and practical solutions for cultivation.