Trichoderma asperellum in the biocontrol of Lasiodiplodia theobromae and Pseudofusicoccum kimberleyense

Abstract

Lasiodiplodia theobromae and Pseudofusicoccum kimberleyense are pathogens causing trunk canker in Carya illioniensis and there are still no reports of effective forms of control. However, biological control is a promising measure. The objective of this work was to isolate, identify and evaluate the action of Trichoderma spp. in the in vitro con-trol of L. theobromae and P. kimberleyense and to identify the compounds produced by the antagonist. Trichoderma spp. was identified by molecular technique and morphologically characterized. The antagonistic action of T. asperellum isolates (obtained from the rhizospheric soil, and of an isolate obtained from a commercial formulation) was evaluated by pairing cultures and volatile metabolites on L. theobromae and P. kimberleyense . Optimization of the cultivation method of T. asperellum was carried out and the compounds produced by the antagonist were identified by gas chromatography. Isolates obtained from the soil were identified as T. asperellum and decreased mycelial growth of L. theobromae and P. kimberleyense in the crop pairing test (48.98% S6 x Qt), as well as by volatile metabolites (29.85% SM21 x TR4). The cultivation conditions that generated the filtrates with the greatest antifungal action used 20 g · l –1 of corn maceration water, yeast extract 7.5 g · l –1 , pH 5, agitation 100 rpm, sucrose 50 g · l –1 , inoculum concentration 10 5 spores /ml. Among the identified compounds, some stood out for having bioactive action, such as pyran derivatives, celidoniol, deoxy, pentadecanoicacid, 2,3-dihydro-3,5-dihydroxy-6-me-thyl, propanoicacid, 1-methylethyl ester and 9-octadecenoic acid. The T. asperellum isolates showed potential for biocontrol in vitro , acting by different mechanisms.