Attività cellulosolitica di specie di Trichoderma e interazione pianta patogeno

The genus Trichoderma comprises a great number of species and strains able to contain plant diseases through multiple mechanisms, which can act directly towards the pathogen (competition, parasitism and antibiosis) or indirectly through the plant. Concerning the plant, Trichoderma spp. may be defined as beneficial microorganisms, since they promote growth and stimulate defensive mechanisms. The production of enzymes such as cellulases serves likely several functions in Trichoderma strains used in biocontrol. The lytic properties of cellulases may be connected to direct inhibition of Chromista pathogens or to colonization of plant roots. The aim of this study was to verify the cellulolytic activity of some Trichoderma strains, their antagonism against Fusarium culmorum and hizoctonia solani in vitro, on potato dextrose agar, and in vivo, on maize seedlings. The cellulolytic activity (endo-1,4-b-glucanase) of 64 strains was tested through the degradation of Na-carboximethylcellulose as substrate. All strains, except two, showed variable enzyme activity from low to high level. Three strains, J40, MART2 and SAL1, were selected for their different cellulolytic activity (no activity, medium activity and high activity, respectively) and were used to study their interaction with each pathogen ì) in vitro, using the dual culture plate assay and ìì) in vivo, by their application on corn seed to control the disease caused by the two pathogens, artificially inoculated on roots. In vitro, MART2 and SAL1 strains inhibited colony radial growth of both pathogens more than J40. All three strains inhibited more F. culmorum than R. solani. Moreover, all strains showed at microscope examination parasitism action mechanism against F. culmorum and R. solani hyphae consisting in, coils, cell lysis and cell wall collapse. In vivo, all Trichoderma strains reduced the severity of disease caused by both pathogens. They were similarly effective against R. solani, whereas J40 and MART2 were more effective against F. culmorum disease. SAL1 was more effective against R. solani than F. culmorum. J40, MART2 and SAL1 exhibited root colonization ability. In conclusion, the three tested Trichoderma strains could be good candidate for further studies on plant disease biocontrol.