Exploring the synergistic potential of Trichoderma gamsii T6085 and Clonostachys rosea IK726 for biological control of Fusarium head blight in wheat.

We explore the combined use of two beneficial fungal isolates, Trichoderma gamsii T6085 (Tg) and Clonostachys rosea IK726 (Cr), to enhance Fusarium head blight (FHB) management by biological control. We found no evidence for mycoparasitism or inhibition via diffusible metabolites, but Tg volatiles inhibited Cr growth slightly. Although Cr reduced Tg spore germination and mycelial growth in liquid culture, this effect seemed absent in planta. The BCAs differently modulated defence-related (DR) genes when colonizing roots or spikes. At seven days post-inoculation (dpi), root-applied Cr, alone and co-inoculated, induced a minor upregulation of PR1. In leaves, a systemic signalling response by root inoculation was detected. In spikes, Pal1, PR1, and Lox1 were upregulated by Cr alone and co-inoculated at 96 hours post-inoculation (hpi). However, Lox1 activation was enhanced by co-inoculation. On spikes inoculated with Fg, the BCAs revealed different patterns of DR gene modulation indicating involvement of different biocontrol mechanisms. In detail, Pgip2 was primarily upregulated at 24 hpi in co-inoculated spikes whereas at 72 hpi activation of DR genes was observed only with Tg. Notably, the disease incidence was reduced by 93 % by co-inoculation. In addition, the inoculum potential of F. graminearum on straw was reduced by all BCAs treatments, with ≥ 96 % reduction of perithecia after six months incubation. Our results show the potential of combining Tg and Cr as a more effective and stable FHB management strategy, than by treatments with the individual strains.