The use of Trichoderma spp., Pseudomonas fluorescens, and Bacillus spp. in Seed and Soil Treatment

The rhizosphere colonizing fungi, Trichoderma harzianum and T. viridae, and the rhizosphere colonizing bacterium, Pseudomonas fluorescens, have been widely incorporated into IPM crop protection packages for several vegetable crops in Honduras, Ecuador, Indonesia, Kenya, the Philippines, India, Nepal, and Bangladesh. The rhizosphere colonizing bacterium, Bacillus subtilis, and other Bacillus spp. have been used less widely but have proven to be valuable components in IPM programs. Trichoderma species have been used in soil treatment, seedling dips, and in “Trich-composts” or “Tricho-leachates” to provide protection from soilborne fungal pathogens, including Pythium, Rhizoctonia solani, Sclerotium rolfsii, Phytophhora, and Fusarium sp., and nematodes including Meloidogyne incognita and M. javanica. P. fluorescens has been used as a seed treatment or soil treatment for protection against soilborne fungal pathogens. Bacillus sp. provides both direct growth promotion and control of soilborne pathogens. The mechanisms whereby Trichoderma sp. controls pathogens include the production of antibiotics, direct parasitism, and the induction of systemic resistance via the salicylic acid signaling pathway. In addition, these fungi improve phosphorous and nitrogen uptake, improve root growth and water uptake, and detoxify HCN produced by deleterious rhiozosphere inhabiting bacteria. Trichoderma induced resistance has been shown to control soilborne fungi, foliar and bacterial pathogens, and some viruses. Pseudomonas fluorescens provides control by production of antibiotics and chelation of Fe⁺⁺⁺ in the rhizosphere and by induction of systemic resistance via the jasmonic acid/ethylene signaling pathway. Fe⁺⁺⁺ is needed by many soilborne fungi for their growth and pathogenicity, and Pseudomonas-produced siderophores essentially make available Fe⁺⁺⁺ unavailable to pathogens near the root system. The induction of systemic resistance has been shown to make the plants less desirable as food sources for control of fungal and bacterial foliar pathogens and for virus control by directly interfering with infection, cell to cell and systemic virus movement, and virus replication. The presentation will show the results from several countries of using locally-produced products in farmers’ fields.