In Vitro and in Planta Evaluation of Trichoderma asperellum TA as a Biocontrol Agent Against Phellinus noxius , the Cause of Brown Root Rot Disease of Trees

Brown root rot (BRR), caused by the white rot fungus (syn. ), is an epidemic disease of diverse broadleaved and coniferous tree species in many tropical and subtropical regions. Flooding and trenching control measures are difficult to implement, and chemical controls can have an adverse impact on ecosystems. Previous studies have provided in vitro evidence for the potential use of spp. for biocontrol of BRR. Here, we analyzed the in vitro antagonistic and mycoparasitic abilities of four spp. isolates against four isolates in dual culture and wood blocks. A convenient inoculation system based on root inoculation of a highly susceptible loquat ( ) with -colonized wheat-oat grains was developed to examine the effect of treatment in planta. Preventive application of TA, the isolate showing high antagonistic activity in vitro, was effective in preventing and delaying the wilting of -inoculated loquat cuttings in greenhouse trials. To understand the specific niche in which TA interacts with , KOH-aniline blue fluorescence microscopy was used to investigate the colonization of loquat roots by and/or TA. Dilution plating assays were also conducted to quantify populations in the rhizosphere and potting mix. TA was able to robustly establish in the rhizosphere and potting mix but with scarce root penetration limited to the superficial layer. We discuss the timing and strategy for applying antagonistic sp. on living trees or in BRR-infested areas for BRR management.