Screening, identification and evaluation of Trichoderma spp. for biocontrol potential of common bean damping-off pathogens

Damping-off caused by soil-borne pathogenic fungi is the major constraint responsible for significantly reduced yields and severe economic losses during common bean cultivation. In a search for alternative control measures, this study describes the investigation of 85 Trichoderma isolates obtained from bean rhizospheric soil to identify an environment friendly method of biological control of damping-off. The Trichoderma isolates were screened for their antagonistic potential against four common bean pathogens namely Fusarium oxysporum, Fusarium solani, Macrophomina phaseolina and Pythium ultimun. As a result, 6 Trichoderma isolates were selected and further identified as T. asperellum It-13, T. koningiopsis It-21, T. erinaceum It-58, T. gamsii It-62, T. afroharzianum P-8 and T. harzianum P-11 by amplifying the sequences of ITS1 and ITS4. Identified strains were found to produce volatile and non-volatile inhibitory metabolites as well as hydrolytic enzymes (chitinase, cellulase, protease and lipase) with T. gamsii It-62 exhibiting globally the highest enzyme secretion. Seeds treatment with T. gamsii showed a beneficial effect on the emergence of bean plants by inhibiting damping-off incidence and delaying the onset of disease symptoms induced by the different plant pathogens. As far as we know, this is the first report in Cameroon referring to the antagonistic effect of Trichoderma gamsii on soil-borne pathogens complex causing damping-off of common bean. It could be suggested that T. gamsii It-62 should be further investigated as a promising alternative to control common bean damping-off caused by plant pathogens.