Prehaustorial local resistance to coffee leaf rust in a Mexican cultivar involves expression of salicylic acid-responsive genes

In Mexico, coffee leaf rust (CLR) is the main disease that affects the Arabica coffee crop. In this study, the local response of two Mexican cultivars of (Oro Azteca and Garnica) in the early stages of infection was evaluated. We quantified the development of fungal structures in locally-infected leaf disks from both cultivars, using qRT-PCR to measure the relative expression of two pathogenesis recognition genes ( and ) and three genes associated with the salicylic acid (SA)-related pathway ( , and ). Resistance of the cv. Oro Azteca was significantly higher than that of the cv. Garnica, with 8.2% and 53.3% haustorial detection, respectively. In addition, the ( ), a key gene for the pathogen recognition, as well as the genes associated with SA, , and , presented an increased expression in response to infection by in cv. Oro Azteca if comparing with cv. Garnica. Our results suggest that Oro Azteca's defense mechanisms could involve early recognition of CLR by NDR1 and the subsequent activation of the SA signaling pathway.