Abstract:
Trichoderma spp. are known biocontrol agents for many plant pathogens,
especially against soil-borne pathogens. Trichoderma is also involved in
salinity and drought tolerance of plants. The main objective of this study was
to screen Trichoderma isolates to use them as potential biocontrol agents in
agricultural fields under various salinity and drought conditions. For this
purpose, screening of salinity and drought tolerance of Trichoderma isolates
having plant growth promotion traits and antagonistic effects on Sclerotium
rolfsii and Fusarium oxysporum f. sp. cubense were explored under in vitro
conditions. In total, 36 Trichoderma isolates were isolated from various
climatic zones in Sri Lanka. They were screened for salinity tolerance using
different strengths of NaCl-amended PDA plates. Trichoderma Tmat2 was
found to be the most salinity-tolerant isolate followed by T9 and T13. Drought
tolerance was screened on KCl-amended PDA for osmotic potential and
polyethylene glycol (PEG) for matric potential. Based on the results, Tmat2
and Tmaho4 isolates were found to be the best drought tolerance isolates
whilst T9 and T13 were found as moderately drought tolerance isolates. All
strains were screened for antagonistic activity by using Sclerotium rolfsii and
Fusarium oxysporum f. sp. cubense as challenging fungal pathogens. Isolates
T9, T13 and Tmat2 were found to be the most powerful antagonistic isolates
and showed higher chitinolytic activity on plate assay. According to the IAA
assay, Tmat2, Tkal1 and T13 showed the highest indole acetic acid production.
However, in the phosphate solubilization assay T9, T13, Tmaho4 and Tuni2
showed the highest ability of phosphate solubilization. Accordingly, it can be
concluded that Trichoderma T13 would be the best candidate to be developed
as a biopesticide for field application under salinity and drought conditions
considering the overall performances with IAA production, phosphate
solubilzation and antagonistic potential.
