Testing plant growth promoting microorganisms in the field - a proposal for standards

Abstract

In the European Union and worldwide there are a burgeoning markets for plant growth promoting microorganisms (PGPM) and other biological agents as soil improvers, bio-fertilizers, plant bio-stimulants, and biological control agents or bio-pesticides. Microbial agents have a major share in this development. The use of such products is often advertised with the promise of contributing to sustainable agricultural practices by increasing crop growth and yield and offering an alternative or substitute to decrease the dependency of agriculture on hazardeous agrochemicals. In contrast to registered microbial plant protection products, PGPM that are marketed in the EU as soil improvers or plant biostimulants, are not strictly required to have proven minimum efficacy levels under field conditions. Manufacturers only have to ensure that these products do not pose unacceptable risks to human, animal or plant health, safety or the environment. Uniform guidelines comparable to the EPPO - standards (European and Mediterranean Plant Protection Organisation) to test the efficacy in field trials are not available. This paper attempts to fill the gap. It proposes guidelines for PGPM field trial design and implementation, as well as recommendations for the type and scope of data collection and evaluation. Selected research papers from literature were evaluated to analyze, whether and to what extent the requirements are already met. The majority of the papers had a clear experimental design followed by proper data evaluation. Frequent deficiencies were the low number of tested environments and crop species, insufficient site and agronomic management description and missing data on soil humidity and temperature. Using the suggested standards is assumed to increase the expressive power of tested microbial products.

Chickpea seed endophyte Enterobacter sp. mediated yield and nutritional enrichment of chickpea for improving human and livestock health

“…Enterobacter strains with PGP properties are thought to work through a variety of mechanisms ( 34 , 52 ). The most important mechanism is the synthesis of PGP- hormones such as indole-3 acetic acid (IAA), which can stimulate root growth and enhance nutrient uptake by the plant ( 16 ). Another mechanism is through the production of enzymes such as phosphate, K, and zinc solubilizing enzymes, which can release nutrients from organic sources in the soil and make them available to the host plants ( 12 , 17 , 35 ).…”

“…PGPMs have been successfully used either as biofertilisers or as bio-pesticides for a very long time ( 16 ). However, the application of the seed endophytes to plant growth promotion (PGP) and their impact on the improving nutrient quality of the host plant are very poorly studied ( 8 ).…”