Controle genético e químico da ferrugem do cafeeiro e sua relação com a expressão da doença, produtividade, composição química, atividade antioxidante e qualidade do café

Abstract

The objective of this study was to verify the efficiency of rust genetic and chemical control and its influence on disease progress and coffee yield, the effects of rust and its control forms on the activity of antioxidant enzymes and metabolite levels of leaves and fruits and on leaf mineral composition, in addition to evaluating the effects of rust expression and its control forms on coffee quality. The experiment was conducted in the Germplasm Active Bank of Coffea spp., in Minas Gerais, Brazil, in the Experimental Field of Patrocínio (CEPC). Four arabica coffee genotypes wre evaluated, from the groups Híbrido de Timor (HT) (MG0277 and MG0313) and Bourbon (MG0006 and MG0012), with and without chemical treatment for rust control (Verdadero 600 WG® - Cyproconazole + Thiamethoxam, 1.0 kg.ha-1). In plants not treated for rust control, the leaf miner was controlled (Actara 250 WG®, Thiamethoxam, 1.0 kg.ha-1). The assessments of rust incidence and severity, as well as the collection of leaves and fruits for analysis of enzymatic activity and of fruits for chemical analysis occurred when the fruits were green, sugarcane-green and ripe. After harvesting, leaves were collected for leaf mineralogical analysis of macro-and micronutrients. Yields in bags of processed coffee per hectare (SC ha-1) were measured by weighing the processed coffee after drying (12% moisture). After dry processing and sample preparation, chemical and physical evaluations of the bean and sensory assessments of the beverage were carried out. All evaluations were performed in the 2018/19 harvest. There is variability in the HT group for rust resistance, with MG0277 resistant and MG0313 susceptible. Genetic control is at least as efficient as chemical control, with a differential response of genotypes to the use of pesticides. There was no effect of chemical control on yield in the first harvest after infestation and the genotypes showed similar yield, with or without the use of pesticides. Chemical control does not affect nutrient content in the leaves, but rust expression is associated with the content of these nutrients. The activity of antioxidant enzymes and the levels of metabolites in leaves and fruits are related to rust expression and are affected by the type of control and ripening stage, indicating a systemic response of the plant to the infection. Genetic and chemical controls are effective in reducing the damage caused by the disease in bean composition. Genotypes with resistant ancestry, even with resistance breakdown, respond better to chemical control, reflecting positively on bean and beverage quality. The chemical and physicochemical components of beans that were affected by rust are associated with attributes evaluated by sensory analysis. Coffees with a higher and lower frequency of “fruity” and “chocolate” flavor notes, respectively, such as HT, have a higher total score in sensory analysis, regardless of the use of chemical control. The combination of genetic and chemical control favors an increase in the sugar content in the beans, the total sensory score and the richness of perceived flavors.