Trichoderma viride establishes biodefense against clubroot (Plasmodiophora brassicae) and fosters plant growth via colonizing root hairs in pak choi (Brassica campestris spp. chinesnsis)

The significant economic importance of the pak choi crop leads farmers to take numerous measures to combat the club root disease, which is harmful to Brassicaceae plants. The mechanical understanding of clubroot biocontrol, on the other part, is still largely unknown. The fundamental criterion for choosing rhizospheric strains obtained from tomato was the germination inhibitory activity of Plasmodiophora brassicae resting spores. The resting spores of the clubroot causing pathogen were inhibited by 10 fungal isolates. TR-7 had the strongest inhibitory impact, reducing spore germination to 25.3 %. The plant growth promoting and extracellular enzyme activities of the fungal strain TR-7 were investigated. TR-7 produced indole acetic acid (IAA), as well as side-rophore and extracellular enzymatic activities. Inoculation with strain TR-7 improved pak choi plant growth in greenhouse settings when compared to plants grown without TR-7 and P. brassicae infected plants. During fungal association, the activity of lactate dehydrogenase (LDH), alcohol dehydrogenase (ADH), and malate dehydrogenase (MDH) was dramatically enhanced in clubroot infected plants. Co-inoculation including both P. brassicae and TR-7 showed 56.7 % decline in gall growth when compared to plants only infected with P. brassicae. Multiple treatments of TR-7 were more efficient than one treatment at repressing root hair infes-tation in clubroot infected plants at 7, 14, and 21 days after inoculation (DAI). TR-7 was identified as Trichoderma viride based on the internal transcribed spacer (ITS) sequence analysis. The findings show that the application of T. viride as bio-fungicides provides another potential promising strategy for suppressing clubroot disease in pak choi.