Metabolismo de compostos constitutivos e a resistência à ferrugem em diferentes cultivares de cafeeiro

Abstract

One of the most important diseases of coffee is rust, caused by the fungus Hemileia vastatrix. The use of pathogen resistant cultivars is a way for the producer to avoid the damage caused by the disease without the use of fungicides. However, there are still many questions about the mechanisms by which plants are resistant. From this, the present work aimed to analyze the relationship between the constitutive metabolism of phenolic compounds and alk aloids and resistance to rust in resistant and susceptible coffee cultivars. The cultivars used in the experiment were: Aranâs RV, IAPAR 59, Clone 224, Clone 312, Conilon 213 (resistant to rust) and Mundo Novo 376/4 (susceptible to rust). The plants of the experiment were in their first productive year and the collection of the vegetal material was carried out between October and November, after the first rains. At this time there was still no pathogen present in the field. The objective of the collection in this period was to collect mature, stable and uniform leaves between the different cultivars to evaluate the difference in constitutive gene expression, as well as to quantify some phenolic compounds in the six coffee cultivars with different resistance levels to rust. For this, relative gene expression analyzes of the PAL, CAD and POX genes for the phenylalanine ammonia lyase, cinnamyl alcohol dehydrogenase and peroxidase enzymes, respectively, present in the phenylpropanoid route were performed. Quantifications of lignin, total soluble phenols, total soluble solids, chlorogenic acid, caffeine and trigonellin in coffee leaves were also performed. In all analyzes, there were generally no differences between resistant and susceptible cultivars, perhaps because rust-resistant coffee plants did not constitutively produce more compounds related to plant defense than susceptible ones as a form energy saving and better use of the resources it has for its development at that time. From the results obtained in the present work, it was concluded that there is no relation between the constitutive relative expression of the PAL, CAD and POX genes, constitutive concentration of lignin, total soluble solids, total soluble solids, chlorogenic acid, caffeine and trigonellin in leaves, and resistance to coffee rust in the cultivars tested in this experiment.