Seleção in vitro de nanopartículas, óleos essenciais e fungicidas para o controle de Ceratocystis manginecans

Abstract

The Ceratocystis species are considered of great phytopathological importance in several plant species, both annual and perennial. These pathogens cause cankers and black rots on stems and roots, with consequent wilting, drying and death of the plants. The Ceratocystis canker, caused by Ceratocystis manginecans, has recently been reported in coffee crops. C. manginecans is an important pathogen due to its aggressiveness in non- resistant plants, and strategies to reduce damage need to be established. The management of diseases in economically important plants, such as coffee, requires a good understanding. The present study aimed to select in vitro nanoparticles, essential oils, and fungicides for the control of C. manginecans. Four experiments were carried out, the first to test the fungicides thiophanate methyl, tebuconazole, azoxystrobin, cyproconazole, azoxystrobin + cyproconazole, mancozeb and copper hydroxide. The second, CuO, ZnO, S and MoO3 nanoparticles (NP’s). The doses, of experiments 1 and 2, were 0; 2.5; 10; 40; 160; 320 and 640 mg/Kg-L. The third, the essential oils of Melaleuca alternifolia, Eremanthus erythropappus, Thymus vulgaris, Eucalyptus radiata and Cymbopogon citratus, at doses of 0; 100; 200; 400; 1600 and 3200 μL/L. The fourth was based on the best treatments and least sensitive isolates obtained in the above experiments. Five isolates of C. manginecans (KLC1, P14, P311, P711 and P811) were used. Mycelial discs were placed in the center of Petri dishes with the culture medium modified with the treatments and measurements of the colony diameters were performed. The data obtained were used to calculate the percentage of mycelial growth inhibition and the dose required to reduce growth by 50% (EC50). In experiment I, thiophanate methyl and cyproconazole were classified as highly toxic (EC50 <1 mg/Kg-L), with 100% mycelial inhibition of the isolates from doses of 2.5 and 40 mg/Kg-L, respectively. In experiment II, none of the NP doses inhibited mycelial growth by 100%, however, the isolates were more sensitive to MoO3 NP’s, followed by ZnO and CuO. In experiment III, 100% inhibition was only observed with C. citratus oil, from 1600 μL/L. The second best performance was obtained by T. vulgaris, followed by M. alternifolia. In experiment IV, the isolates were more sensitive to chemical control compared to other alternative methods. There was a difference in sensitivity between the isolates and KLC 01 and P14 were the least sensitive to treatments.