In vitro evaluation of Trichoderma asperellum Samuels, Lieckfeldt & Nirenberg strains as promising agents for the control of Alternaria solani Sorauer

Abstract

The aim of this work was to evaluate in vitro antagonism of 13 Cuban Trichoderma asperellum Samuels, Lieckfeldt & Nirenberg (Ta.) strains against Alternaria solani Sorauer. The modes of action of T. asperellum strains against A. solani in dual culture were determined. The results showed differences between the antagonist strains. The strains Ta. 90, Ta. 78, Ta. 75, and Ta. 85 were highlighted by their antibiotic effect. In the space competition, only Ta. 85 colonized 100 % of the pathogen (Bell et al. scale Grade 1.), while Ta. 17, Ta. 3, Ta. 90, Ta. 78, and Ta. 28 had more than 80 % growth over A. solani (Grade 2 of the scale). However, Ta. 75, Ta. 78, Ta. 79, and Ta. 85 strains proved to be good space competitors against the pathogen, with more than 50 % inhibition of radial growth of the pathogen. The strains Ta. 13, Ta. 56 and Ta. 85 had four hyphal interactions with A. solani; the most observed were vacuolization, penetration and granulation. The strains Ta. 1, Ta. 3, Ta. 12, Ta. 13, Ta. 25, Ta. 28, Ta. 56 and Ta. 85 caused significant reduction of the area occupied by the pathogen at 400 h, relative to the size at 96 h. The strains Ta. 85, Ta. 1 and Ta. 12 were highlighted in this action; the strain Ta. 85 was selected as the most promising; however, Ta. 28, Ta. 56 and Ta. 13 showed good qualities for evaluation in field conditions.