In vitro evaluation of Trichoderma isolates as biocontrol agents against Rigidoporus microporus (Fr.) overeem causing white root disease in cinnamon.

Abstract

White root disease (WRD) caused by Rigidoporus microporus is a looming threat to cinnamon cultivations in Sri Lanka. The use of synthetic fungicides currently employed to control the disease is not compatible with the organic production of cinnamon. The current study was conducted to isolate Trichoderma species from cinnamon rhizosphere soils and to morphologically identify them and to screen the antagonistic effect of Trichoderma isolates obtained from rhizosphere soils of cinnamon, banana, and pepper against the causative agent of white root disease in cinnamon. Antagonistic activity of eight isolates was assessed employing a dual culture assay. Among these isolates, four were obtained from the rhizosphere soil of cinnamon (MA1, MA2, MA3, and MA4), while the remaining isolates were obtained from the rhizosphere soil of bananas (Tc, Tk, and T13) and pepper (MT). All dual culture assay plates were incubated for five days at 28 C, and percentage inhibition of the radial growth of R. microporus mycelium was recorded. The findings unveiled considerable variations in the antagonistic capacity across the isolates. Statistical analysis revealed that the MA1 isolate exhibited a considerably greater efficacy in inhibiting the mycelial growth of R. microporus by 44.12 % at p≤0.05, compared to the other isolates used in the study. The MA2 isolate exhibited the lowest percentage inhibition (22.06%). This study revealed the feasibility of using Trichoderma isolates as effective bio control agent against R. microporus under in-vitro conditions. Screening of more Trichoderma strains and appropriate in-vivo testing is necessary to explore the possibility of applying potential Trichoderma species for controlling the WRD in cinnamon.