Abstract:
Species in the genus Trichoderma are important
commercial source of several enzymes, biofungicides
and growth promoters. The most common biological
control agents of the genus are strains of T. harzianum,
T .viride and T. viriens. In this study, sixteen selected
isolates of T. harzianum from different land use types
in Embu, Kenya were tested for antagonistic action
against five soil borne phytopathogenic fungi
(Rhizoctonia solani, Pythium sp, Fusarium
graminearum, F. oxysporum f. sp phaseoli and F.
oxysporum f. sp Lycopersici) using dual culture assay
and through production of non-volatile inhibitors.
Seven isolates were further characterized using
RAPD-PCR procedure to determine genetic
variability. All T. harzianum isolates had considerable
antagonistic effect on mycelial growth of the
pathogens in dual cultures compared to the control.
Maximum inhibitions occurred in Pythium sp-055E
interactions (73%).The culture filtrates obtained from
Czapek‟s liquid medium reduced the dry weight (mg)
of the mycelia significantly while those from the
potato dextrose broth showed minimum inhibition
growth. Pythium sp. was most sensitive compared to
other pathogens. Genetic similarities generated using
Jaccard‟s coefficient of similarity ranged from 0.231
to 0.857 for isolates 055E, 011E, 010E and 015E.
Since all T. harzianum isolates evaluated were
effective in controlling colony growth of the soil borne
pathogens both in dual cultures and in culture filtrates
they could be tried as a broad spectrum biological
control agent in the green house and under field
conditions.
Key words: Trichoderma harzianum, growth
antagonism, genetic similarity RAPDs
