Abstract
The use of novel isolates of
Trichoderma
with efficient antagonistic capacity against
Fusarium oxysporum
f. sp
. lycopersici
(FOL) is a promising alternative strategy to pesticides for tomato wilt management. We evaluated the antagonistic activity of 30 isolates of
T. asperellum
against 4 different isolates of FOL. The production of extracellular cell wall degrading enzymes of the antagonistic isolates was also measured. The random amplified polymorphic DNA (RAPD) method was applied to assess the genetic variability among the
T. asperellum
isolates. All of the
T. asperellum
isolates significantly reduced the mycelial growth of FOL isolates but the amount of growth reduction varied significantly as well. There was a correlation between the antagonistic capacity of
T. asperellum
isolates towards FOL and their lytic enzyme production. Isolates showing high levels of chitinase and β-1,3-glucanase activities strongly inhibited the growth of FOL isolates. RAPD analysis showed a high level of genetic variation among
T. asperellum
isolates. The UPGMA dendrogram revealed that
T. asperellum
isolates could not be grouped by their anta- gonistic behavior or lytic enzymes production. Six isolates of
T. asperellum
were highly antagonistic towards FOL and potentially could be used in commercial agriculture to control tomato wilt. Our results are consistent with the conclusion that understanding the genetic variation within
Trichoderma
isolates and their biochemical capabilities are required for the selection of effective indigenous fungal strains for the use as biocontrol agents.