A Novel Pesticide Vectorization Strategy: Development of Phloem-Mobile PCA Amide Derivatives for Enhanced Crop Disease Control

The phloem mobility of fungicides is a highly advantageous property for controlling plant root and vascular diseases. In order to develop phloem-mobile fungicides with enhanced antifungal activity, a new pesticide vectorization strategy was proposed for using exogenous compounds as vector groups in this study. Nine novel PCA amide derivatives containing heterocyclic carboxylic acids were designed and synthesized by coupling PCA with a heterocyclic carboxylic acid via an amide linkage. In vitro bioassays revealed that nine target compounds exhibited moderate to strong antifungal activity against the tested fungal pathogens. Notably, compound D4 demonstrated superior inhibitory effects against multiple pathogenic fungi. The results of phloem mobility tests demonstrated that five target compounds, D1, D2, D4, D7, and D9, exhibited phloem mobility, which is consistent with possible carrier-mediated transport. In pot experiments, compound D4 exhibited significantly better protective and curative efficacy against rice sheath blight than PCA, a benefit that may stem from its phloem mobility. Further systemic translocation studies in tobacco (Nicotiana tabacum L.) confirmed that compound D4 is readily absorbed by leaves and efficiently distributed throughout the plant, with pronounced accumulation in roots and stems. This translocation pattern may play a significant role in improving the effectiveness of compound D4 in controlling root and vascular diseases.