Resistance of genotypes and defence compounds against bacterial halo blight of coffee

Bacterial halo blight of coffee (BHB), caused by Pseudomonas syringae pv. garcae, is one of the main coffee diseases and is economically important mainly in regions of higher altitudes and mild temperatures. The use of resistant cultivars in the management of diseases is the most efficient and least costly technology for producers. The Coffee Germplasm Bank of Minas Gerais State has genotypes with great genetic variability, some of which are sources of resistance to several diseases and pests. Thus, the objective of this study was to evaluate the potential of 34 genotypes from the Coffee Germplasm Bank of Minas Gerais State and five cultivars with resistance to BHB. We evaluated the expression of three plant defence genes (phenylalanine ammonia liase-PAL, peroxidase-POX, and cinnamyl alcohol dehydrogenase-CAD) and quantified the content of total soluble phenolic compounds, lignin, caffeine, trigonelline, and chlorogenic acid in coffee leaves showing different levels of resistance to BHB. The cultivar IPR 102 (resistant control to BHB), the Catimor UFV 7158, Caturra Vermelho x CIFC H 79/1 UFV 339-34, Catigua MG2, Volutifolia Vermelho, Caturra Vermelho, Hibrido de Timor UFV 432-02, Caturra Vermelho x CIFC H 288/14 UFV 319-04, and Caturra Vermelho x CIFC H 79/1 UFV 339-02 genotypes showed low disease severity. The UFV 7158 genotype showed higher PAL and POX expression levels than Mundo Novo 376/4 cultivar. The IPR 102 cultivar and UFV 7158 genotype showed high chlorogenic acid content and low caffeine and trigonelline contents.