Host Specificity of the Bioherbicidal Fungal Strain Paramyrothecium eichhorniae TBRC10637 for Control of Water Hyacinth

Paramyrothecium eichhorniae TBRC10637 has been reported as a potential biocontrol agent of water hyacinth (Eichhornia crassipes) in Thailand. Despite its great potential, it remained unclear whether the strain may cause disease in other plant species, especially those sharing the same niche as water hyacinth. Here, we examined the strain for its specificity and pathogenicity on 55 plant species from 26 families ranging from crop plants to aquatic weeds. We showed that, except for water hyacinth, P. eichhorniae TBRC10637 did not cause leaf spot or leaf blight or on any of the tested plants. Scanning electron microscopy of spores inoculated on eight plant species, including economically important plants such as maize (Zea mays) and chilli (Capsicum annuum) at 0, 24, 48, and 72 h after inoculation, showed no spore germination, except on water hyacinth. Inoculation with spore-free culture washing led to blight symptoms on leaves of water hyacinth 72 h after inoculation, suggesting that enzymes and secondary metabolites may be involved in causing the blight symptoms. Our results confirmed high specificity of P. eichhorniae TBRC10637 towards water hyacinth, paving the way to control the spread of water hyacinth effectively.