Seed treatment techniques for biological control agents in the control of charcoal rot of soybean (Macrophomina phaseolina, Trichoderma harzianum, Trichoderma koningii)

The soil pathogen Macrophomina phaseolina is the causal organism of the disease, charcoal rot of soybean. This fungus causes external as well as internal damage to its host. Infection by this pathogen often reduces soybean yield and seed quality.; This study was conducted to determine if an inoculation procedure for soybean seed biological control agents could be developed for use in large farming operations. The biological control agents, Trichoderma harzianum and T. koningii, were applied with lime, peat, or starch to soybean seed. Treated seed were planted into soil infested with M. phaseolina. Isolation ratings of Trichoderma spp. and M. phaseolina from soybean root tissue were determined, and the viability of T. harzianum and T. koningii in combination with protectants was evaluated over 12 wk in simulated commercial storage (SCS).; Throughout greenhouse studies, no seed treatment containing either Trichoderma spp. effectively reduced isolation ratings of M. phaseolina from soybean seedling root tissue. T. harzianum had greater viability in SCS and was isolated more frequently from root tissue compared to T. koningii. Without a protectant, T. koningii viability in SCS was reduced to zero within 12 wk; however, addition of any protectant provided for some level of sustained viability.; Additional research should be conducted to determine conditions for increased viability of Trichoderma spp. over time in SCS and increased isolation ratings for T. koningii or T. harzianum from soybean seedling root tissue. T. harzianum and T. koningii were isolated from root tissue in the presence of M. phaseolina; further research should be conducted to determine if these fungi were antagonistic to M. phaseolina.