Enhancement of plant productivity through microbial seed treatments
G. E. HARMAN (1). (1) Advanced Biological Marketing, Geneva, NY, U.S.A.
Microbial seed treatments have been proposed and used now for several decades for the control of plant diseases. In many cases enhanced plant growth and performance was also noted, but the mechanisms of action of action have been unknown. In fact, even the mechanisms of biocontrol have been misunderstood in many cases. Recently, there have been identified a number of microbes that are endophytic plant symbionts, including specific strains of the Ascomycete <i>Trichoderma</i>, and the Basidomycete <i>Piriformospora indica</i>. These fungi colonize the external area of roots and at least some strains grow with the roots and provide season long benefits to crop plants. In addition, mycorhizzal fungi, and plant growth promoting bacteria in the genera <i>Pseudomonas</i> and <i>Bacillus</i>, as well as others, also colonize plant roots. These plant endophytic symbionts have qualitatively similar effects upon plants, and can induce systemic resistance to diseases; induce resistance to plant stresses including drought, salt, and pollutants; increase plant nitrogen use efficiency (NUE), increase plant photosynthetic efficiency, and even increase antioxidants in produce. Selected strains of <i>Trichoderma</i> spp. can be applied as seed treatments and have been shown to reliably increase crop yields over hundreds of trials, and during the drought of 2012, provided remarkable benefits to stricken fields.
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