Comportamento de clones de cajueiro-anão ao oídio e o dano em flores e maturis

Abstract

The powdery mildew, caused by the fungus Erysiphe quercicola, is the main phytopathogenic problem of the cashew tree, damaging the production of chestnut and peduncle. The objective of this work was to evaluate the behavior of three BRS 226, BRS 265 and EMBRAPA 51 dwarf cashew clones in epidemic conditions and the damage of powdery mildew on flowers and maturi. The experiment was carried out in the Experimental Field of Embrapa, in Pacajús - CE, from september to november 2018, through the monitoring of three clones of dwarf cashew, distributed in a completely randomized design (DIC). The incidence was evaluated through the percentage of flowers infected by the pathogen and the severity of the disease in the panicles using a score scale of 0 to 4. With the incidence and severity data, the area under the disease progress curve (AACPD). In addition, the diseases effect variables such as total and maximum number of flowers; the fall rate and the days with flowers; the number of maturis; and damage in flowers and maturis were submitted to analysis of variance and Tukey test at 5%. Also, the disease variables were correlated with the damage and number of total flower by the Pearson Correlations test. According to the disease and disease effect variables, the BRS 226 clone was the one that presented the best and the Embrapa 51 clone had the worst responses regarding the attack of powdery mildew, including damage of 75 and 80% in flowers and cashew nuts, respectively. Clone BRS 265 presented intermediate responses. Disease variables were positively correlated with flower damage and negatively with total flower numbers. The results showed that the BRS 226 clone has resistance to powdery mildew and is shown as a strategy to reduce damage in flowers and maturis.