Selection and control efficacy of Trichoderma spp. against Fusarium solani and Lasiodiplodia theobromae causing root rot in forage cactus

Forage cactus (Nopalea cochinillifera L.) is highly efficient in water use and biomass production for animal feed in arid regions; however, soil fungi Fusarium solani (Fs) and Lasiodiplodia theobromae (Lt) pose a threat to this plant. This study evaluated the antagonistic potential of nine Thricorderma spp. against these pathogens. Thricorderma aureoviride URM 6668 (TIA) significantly decreased the growth of the mycelial halo of Fs and Lt by 34% and 89%, respectively (in vitro). TIA inoculation on forage cactus soils was also compared with the use of isolate T. aureoviride URM 5158 (TCP), a chitinase producer, and with Acibenzolar-S-methyl, a plant resistance inducer (PRI). All treatments were effective to control the pathogens, reducing the lesion area at the basal cladode by up to 96%, while Trichoderma spp. induced significant reductions of reactive oxygen species (ROS) in plant tissues. TIA showed potential for inoculant production due to its high efficacy against Fs and Lt in vitro and in vivo, its easy application directly on the plant neck in the form of conidia suspension, and its fast growth in the laboratory.