Resistência basal e composição química de cultivares de Coffea arabica L. resistentes e suscetíveis à ferrugem

Abstract

Coffea arabica L. is the most economically important coffee species worldwide, recognized for its high-quality drink. This species is the most severely affected by rust, a disease that causes defoliation and losses in production. The most effective control measure to control the disease is the use of resistant C. arabica cultivars, which can be obtained by introgressing rust resistance genes derived from C. canephora or C. liberica. Lignin is a secondary metabolite that provides the first line of defense in plants against pathogens and its content may differ between resistant and susceptible cultivars. Although the interspecific origin provides

resistance to rust, the chemical composition of these cultivars can be affected. Modern rust- resistant cultivars of C. arabica have been little studied and compared in terms of molecular

and chemical aspects. Thus, this study aimed to verify whether the level of constitutive resistance of cultivars is associated with higher or lower levels of gene expression, the activity of enzymes and metabolites involved in lignin biosynthesis. In parallel, to verify whether the interspecific origin of the cultivars influences on the chemical composition, the contents of chemical compounds were compared between cultivars. The samples were constituted of thirteen C. arabica cultivars with different levels of rust resistance, conducted under field conditions. The expression of WRKY1, PAL1, CAD1, and POX1 genes was analyzed using quantitative real-time PCR (RT-qPCR), the activity of PAL, CAD and POX enzymes and the levels of total phenolic compounds and lignin were determined by spectrophotometry. The chemical compounds from leaves and raw coffee beans were determined by high- performance liquid chromatography (HPLC). Cultivars differed statistically for constitutive expression of all genes, the activity of all three enzymes and contents of metabolites. The interspecific origin of cultivars contributed to the increase in 5-ACQ and trigonelline contents of leaves and beans, caffeine of beans, sugars, citric, oxalic, quinic, succinic and acetic acids and the reduction in malic and lactic acids contents. Based on the results, constitutive gene expression, enzyme activity, and defense-related metabolite contents were not associated with resistance levels of coffee cultivars. The chemical composition of cultivars is influenced by their genetic origin. This study may facilitate future research in the selection of genotypes regarding resistance to rust and chemical composition.