Potencial Antagônico de Trichoderma spp. associados a dsRNA contra Colletotrichum guaranicola (Albuq.)

Abstract

Guaran´a is one of the most important crops in the state of Amazonas. Commercially, their use is as refrigerant, however, the industry of Guaran´a has been growing and diversifying its products, including the foreign market. The main disease that affects the culture of guarana is anthracnose, and its etiologic agent, is the pathogen Colletotrichum guaranicola. The main form of anthracnose control is the use of chemical fungicides, but in some regions, which have gained the recognition of organic agriculture, this control measure is not appropriate to the needs of production. Several species of genus Trichoderma, are antagonists used effectively in biological control of some plant pathogens, including the genus Colletotrichum. The presence of dsRNAs is common in fungi, being reported in the literature many studies associating them with various aspects of these hosts: hipovirulence morphological changes, the phenotype “ killer”in yeast, and others changes in these microorganisms. The main objective of this research was investigate the presence and influence of dsRNA on the antagonistic potential of Trichoderma spp. against C. guaranicola. We analyzed 100 isolates of Trichoderma spp., and only one presented dsRNA. The species was determined by sequencing the ITS region of rDNA and its micromorphological aspects (optical and electron microscopy) as Trichoderma asperellum. We proceeded to purify this material by column chromatography on cellulose and digestion with nucleases (DNase I and nuclease S1). To analyze the possible interference of these particles in the antagonistic potential of Trichoderma, the dsRNA was eliminated with sodium deoxycholate, added to PDA medium at a concentration of 200 mg / mL. Tests of antagonism in vitro (by the method of pairing in Petri dishes), showed a difference between inbred strains (with and without dsRNA) against the pathogen. In vivo tests, in plants of Mucuna aterrima, showed no statistical difference between the isolates with and without dsRNA. Morphological alterations were observed betweem isolates with and without dsRNA, the absence of dsRNA showed higher mycelial growth and higher production of spores. Based on these results it was concluded that dsRNA present in T. asperellum interfere in its potential antagonist in vitro tests, but not to its performance in vivo tests.