Assessment of Biocontrol Ability of Trichoderma Isolates Against White Root Disease Caused by Rigidoporus Microporus in Cinnamon Under Laboratory Conditions

White Root Disease (WRD), caused by Rigidoporus microporus, poses a significant threat for cinnamon cultivations in Sri Lanka. The application of synthetic fungicides to manage this disease contradicts the principles of organic cinnamon production. This study aimed to isolate Trichoderma species from the rhizosphere soils of cinnamon, banana, and pepper, identify them morphologically, and assess their antagonistic activity against the WRD pathogen. The research was conducted at the National Cinnamon Research and Training Centre in Palolpitiya, Thihagoda, Sri Lanka. A dual culture assay was employed to evaluate the antagonistic potential of eight isolates: four from the rhizosphere soil of cinnamon trees (MA1, MA2, MA3, and MA4) and four from the rhizosphere soil of pepper (MT) and banana (Tc, Tk, and T13). The dual culture plates were incubated for five days, during which the radial mycelial growth of the pathogen was measured, and the percentage inhibition of this growth was calculated. The results indicated that the MA1 isolate achieved the highest percentage inhibition of radial mycelial growth at 44.12%, while the MA2 isolate showed the lowest inhibition at 22.06%. Importantly, the MA1 isolate significantly inhibited the mycelial growth of R. microporus (p ≤ 0.05) compared to the other isolates.