Eficiência de métodos de inoculação de Ceratocystis manginecans em mudas de cultivares de café arábica

Abstract

Coffee is one of Brazil's main agricultural products, playing a crucial role in the economy by generating employment and income. However, the occurrence and increasing severity of the disease caused by Ceratocystis manginecans, associated with climate change, threatens coffee productivity. Therefore, studies on effective pathogen inoculation methods and the selection of resistant cultivars are essential. Thus, the objective of this study was to evaluate the efficiency of different C. manginecans inoculation methods in seedlings of different Coffea arabica cultivars. The experiment was conducted using a factorial design (4x4+1), with four cultivars (Catuaí Vermelho IAC 144, Catuaí Vermelho IAC 99, Catucaí Amarelo 24/137 and Mundo Novo IAC 379/19), four inoculation methods (spraying of spore suspension with or without stem wounding, deposition of spore suspension droplets and insertion of a mycelial disk-both with stem wounding) and an additional treatment (deposition of a droplet of sterilized distilled water, without inoculum, in a wound on the stem of Catuaí Vermelho IAC 144 seedlings). A randomized block design with four replications was used. Each replication consisted of four seedlings with eight to ten pairs of fully expanded leaves. Disease severity was assessed 30 days after inoculation. The stem of each plant was sectioned vertically and the length of internal cortical discoloration, both above and below the inoculation point, was measured. Severity was calculated by dividing the length of the discoloration by the total stem height and multiplying the result by 100. The experiments were conducted twice. A combined data analysis was performed to verify differences between the experiments. No significant difference (p<0.05) was found between the trials; therefore, the data presented refer to the average of both experiments. The data obtained were subjected to assumption analyses (normality and homogeneity) for variance analysis (ANOVA). Normality and homogeneity were assessed using the Shapiro-Wilk and Bartlett tests. Since the assumptions were met, data were analyzed using ANOVA. When the F-test in ANOVA was significant (p<0.05), variables were subjected to Scott-Knott grouping tests (p<0.05) or orthogonal contrasts with the additional treatment. A significant difference (p<0.001) was found for the contrast between the additional treatment and the factorial design regarding severity. No symptoms of cortical stem discoloration were observed in plants from the additional treatment, which received only water. The most effective inoculation methods involved wounding, particularly the deposition of a sporesuspension droplet (10.40 to 17.19% severity) and spore suspension spraying (11.15 to 16.64%). Among the cultivars, Mundo Novo IAC 379/19 exhibited the lowest severity (9.97 to 10.40%). Therefore, C. manginecans infection in coffee plants depends on wounding. The application of 500 μL of spore suspension at a concentration of 2.5 × 106 spores/mL-1 proved out as the most efficient, rapid and practical inoculation method. The cultivar Mundo Novo IAC 379/19 showed the lowest severity levels.