Efficiency of indoleacetic acid, gibberellic acid and ethylene synthesized in vitro by Fusarium culmorum strains with different effects on cereal growth

Abstract

Three different Fusarium culmorum strains having a pathogenic, a deleterious (deleterious rhizosphere microorganism), or a promoting (plant growth promoting fungus) effect on plant growth were studied for their ability to synthesize in vitro the phytohormones indoleacetic acid (IAA), gibberellic acid (GA), and ethylene. All the phytohormones tested were synthesized in cultures supplemented with wide concentration ranges of glucose and tryptophan or methionine (precursors of phytohormone synthesis). The amounts of these secondary metabolites synthesized by the particular strains were found to be significantly different. The non-pathogenic PGPF strain (DEMFc2) synthesized the highest amounts of IAA and GA, a fact that could be responsible for the growth-promoting properties of this strain. A pathogenic strain synthesized the highest amount of ethylene, which could be responsible for the negative effect of this strain on plant growth. F. culmorum isolates with a high capacity for IAA synthesis also have a high capacity for GA synthesis and irrespective of the growth conditions, a high positive correlation (R > 0.9) between the concentrations of synthesized IAA and GA in F. culmorum cultures was found. It is worth mentioning that the optimal conditions for the growth of F. culmorum isolates and the synthesis of the individual phytohormones differed from one another. The optimal growth conditions were 1.0% of glucose and 9.9 mM of methionine or 6.0 mM of tryptophan. The optimal conditions for ethylene synthesis were 0.5% of glucose and 6.6 mM of methionine, whereas 1.0% of glucose and 9.0 mM of tryptophan were optimal for IAA and GA synthesis.

Synthesis of Indoleacetic Acid, Gibberellic Acid and ACC-Deaminase by Mortierella Strains Promote Winter Wheat Seedlings Growth under Different Conditions

“…The IAA, the main auxin, is crucial for the majority of plant growth and development processes “and it is also a major factor determining the competition between fungal species that occupy the same niche [ 15 ]”. The production of microbial IAA may depend on the presence of its precursor, tryptophan; however, some microorganisms and plants can also synthesize IAA by Trp-independent mechanism [ 20 , 39 ]. According to Quiroz-Villareal et al [ 16 ], this amino acid was identified as one of the components of root exudates.…”

“…It was found that the concentration of IAA in “MV DEM32” cultures was correlated with the initial dose of Trp at “9 °C” and 20 °C “( Figure 3 B,F), but in the presence of 1.5 mM of Trp, the MV DEM32 strain synthesized the highest amount of phytohormone (about 32 µg mL) ( Figure 3 D). Many reports confirmed that even the very small amount of Trp may induce the IAA synthesis, but in fact, the term ‘small dose’ is not clearly defined [ 15 , 17 , 20 , 39 ]. Kumar et al [ 18 ] announced the IAA concentrations in cultures of bacteria with the 4 mM dose of Trp, whereas Khan et al [ 39 ] applied 0.4 mM of IAA precursor.” The optimal dose of Trp recommended for fungal cultures is from 2 mM to 4 mM and the maximal concentration of IAA was usually measured after 60 and 72 h of incubation [ 17 , 40 ], “whereas the lowest threshold value indispensable for auxin synthesis is not defined.…”

“…Phytohormone ethylene plays role in plant development regulation and stress resistance. Moreover, the microbial ACC-deaminase converts the precursor of ethylene (ACC) to the ammonia and α-ketobutyrate and protects plants from excessive concentrations of ethylene [ 20 , 21 , 22 ].…”

Facilitation of olive harvest by microbial indole acetic acid and an enzyme mixture

“…The production of IAA reached 38850 ppm (unpublished data) in consequence of triplicate performed. In the other studies, it was observed that the production rates of various fungi were lower and their incubation periods were longer (Palavan-Unsal, 1993;Yalcinkaya, 1993;Khan et al, 2012;Jaroszuk-Ściseł et al, 2014). The increasing of the production level and the shortness of the incubation period are significant in terms of reducing the production cost.…”

Differences in Production, Composition, and Antioxidant Activities of Exopolymeric Substances (EPS) Obtained from Cultures of Endophytic Fusarium culmorum Strains with Different Effects on Cereals

“…Earlier studies of the three tested strains of Fusarium culmorum showed a clear diversity of their interaction with cereals, colonization of root [58,60] and root border cells [59] and the ability to synthesize toxins [58], CWDEs [63,64] and phytohormones [60,65]. The ability to induce plant resistance has been demonstrated for these Fusarium culmorum strains [58].…”