Selection of resistance inducers for managing Hemileia vastatrix Berk. & Br. in coffee (Coffea arabica L.) seedlings

Coffee leaf rust (Hemileia vastatrix) is one of the most devastating coffee diseases, causing losses ranging from 23% to 50% of the crop. Chemical applications are the most employed control strategies in countries lacking resistant coffee varieties. In the search for new alternatives for integrated management, an in vitro and nursery evaluation protocol was developed for Coffea arabica cv. Caturra plants using the following resistance inducers: acibenzolar-S-methyl, salicylic acid, potassium phosphite, and Harpin protein. These compounds were tested at three concentrations, across three intervals between product application and pathogen inoculation, and in two response signaling pathways (local or systemic) to assess their effects on the in vitro germination of rust urediniospores and disease severity in 6-month-old coffee plants inoculated with the pathogen. In general, all compounds inhibited urediniospore germination and exerted disease control mediated mainly by the concentration of the product with biweekly application intervals and where local responses prevailed more than systemic ones. This study highlights the potential of these compounds as resistance inducers, especially for acibenzolar-S-methyl, where we observed the best effects on disease control. Our findings open new avenues for incorporating resistance inducers into integrated disease management programs to complement fungicide applications.