Microbial Consortia: Promising Probiotics as Plant Biostimulants for Sustainable Agriculture

Multistrain versus single-strain plant growth promoting microbial inoculants - The compatibility issue

“…Based on a large number of studies, multistrain PGPM mixtures appear to have greater effi cacy on improvement of plant growth and/or biological control than single strains. According to the current trend, prerequisites for successful construction of artifi cial microbial mixtures are: 1) use of diverse microorganisms that can promote plant growth and protect plants from biotic or abiotic stress, 2) effi cacy of seed, leaf or root colonization, 3) compatibility among strains in the mixture, 4) use of microorganisms with diff erent modes of action, 5) human and environmental safety, 6) easy application and 7) easy incorporation in an existing management system (Raupach and Kloepper, 1998;Sikora et al, 2010;Bashan et al, 2014;Großkopf and Soyer, 2014;Ahkami et al, 2017) The issue of compatibility among microbial components of a probiotic multistrain mixture is gaining ground and is considered a basic requirement in the engineering of synthetic microbial mixtures applied to plants (Sarma et al, 2015;Friedman et al, 2017;Woo and Pepe, 2018) or humans and animals (Ouwahand et al, 2018). According to the established literature, the microbial components of a PGPM mixture are considered to be compatible when they have no growth suppressive eff ect on each other during their in vitro co-culture, either in contact or in proximity, or during the plant rhizosphere colonization competition assay (Jain et al, 2012;Castanheira et al, 2017;Pangesti et al, 2017;Santiago et al, 2017;Liu et al, 2018).…”

“…Currently, the majority of the PGPMs marketed as biopesticides, biofertilizers and biostimulants are comprised of a single strain, according to the label. However, bacterial and/or fungal multistrain mixtures are gradually becoming popular (Woo et al, 2014;Woo and Pepe, 2018), indicating a general shift in replacing the single strain inoculants. This shift is refl ected in the increasing number of research publications, as discussed above, the boosting of patent fi les depositions and the interest of several companies in developing and launching multistrain microbial mixtures.…”

Can Trichoderma-Based Biostimulants Optimize N Use Efficiency and Stimulate Growth of Leafy Vegetables in Greenhouse Intensive Cropping Systems?

“…Therefore, our results highlight the need to conduct further investigations on this argument to unravel the physiological and molecular mechanism(s) behind the synthesis and accumulation of these secondary metabolisms in edible leafy produce. Finally, future research should also focus on designing ideotype Trichoderma strains and identifying the best combination of crop species × Trichoderma strains for the production of healthy and nutrient-dense foods [33].…”

“…In addition to their activity in overcoming abiotic stresses, some Trichoderma strains, among which those of Trichoderma harzianum, Trichoderma virens, and Trichoderma atroviride, are capable in triggering phytostimulation (i.e., biostimulant action) via a mechanism entailing multifaceted cross-talk communication between root and shoot systems. This includes the transfer of auxins (i.e., indole-3-acetaldehyde, indole-3-carboxaldehyde, and indole-3-ethanol), oligopeptides, volatiles, and other secondary metabolites to the rhizosphere, which augment root branching and nutrient uptake efficiency (P, Fe, Cu, Zn, and Mn) that consequently improve crop performance [23,28,[30][31][32][33]. However, the positive effects in terms of plant growth, tolerance to abiotic stresses, and increased NUE, not only rely on the use of an effective Trichoderma strain, but also depend upon several interacting variables including the method of application (on the seed or root and soil), cropping systems (open field versus protected cultivation), fertilizer management, plant species, and pedoclimatic conditions [23,34].…”

Effectiveness of Plant Beneficial Microbes: Overview of the Methodological Approaches for the Assessment of Root Colonization and Persistence

“…The increasing demand to reduce the use of chemical fertilizers and pesticides for the development of an agri-food system sustainable for environmental and human health, as well as the current shifting in the agricultural legislation of several countries, have led to an expanded use of bioinoculants. Chemical inputs usually alter the natural physico-chemical and biological equilibrium of soil, and microbial consortia used in agricultural management practices could return soil to its natural status (Lucy et al, 2004;Woo and Pepe, 2018). Although the manipulation of soil microbiomes to optimize crop productivity is an ancient practice, it is still little explored, especially regarding mechanistic studies of plant-microbe interactions and microbial persistence in heterogeneous communities in diverse locations, soils, and hosts (Finkel et al, 2017).…”