Phytohormone Production Profiles in Trichoderma Species and Their Relationship to Wheat Plant Responses to Water Stress

Abstract

The production of eight phytohormones by Trichoderma species is described, as well as the 1-aminocyclopropane-1-carboxylic acid (ACC) deaminase (ACCD) activity, which diverts the ethylene biosynthetic pathway in plants. The use of the Trichoderma strains T. virens T49, T. longibrachiatum T68, T. spirale T75 and T. harzianum T115 served to demonstrate the diverse production of the phytohormones gibberellins (GA) GA1 and GA4, abscisic acid (ABA), salicylic acid (SA), auxin (indole-3-acetic acid: IAA) and the cytokinins (CK) dihydrozeatin (DHZ), isopenteniladenine (iP) and trans-zeatin (tZ) in this genus. Such production is dependent on strain and/or culture medium. These four strains showed different degrees of wheat root colonization. Fresh and dry weights, conductance, H2O2 content and antioxidant activities such as superoxide dismutase, peroxidase and catalase were analyzed, under optimal irrigation and water stress conditions, on 30-days-old wheat plants treated with four-day-old Trichoderma cultures, obtained from potato dextrose broth (PDB) and PDB-tryptophan (Trp). The application of Trichoderma PDB cultures to wheat plants could be linked to the plants’ ability to adapt the antioxidant machinery and to tolerate water stress. Plants treated with PDB cultures of T49 and T115 had the significantly highest weights under water stress. Compared to controls, treatments with strains T68 and T75, with constrained GA1 and GA4 production, resulted in smaller plants regardless of fungal growth medium and irrigation regime.

Effect of Trichoderma asperellum on Wheat Plants’ Biochemical and Molecular Responses, and Yield under Different Water Stress Conditions

“…It is well known that Trichoderma increases the tolerance of wheat plants to abiotic stresses such as salinity, waterlogging, and drought [ 6 , 20 , 24 ], although this trait is not an attribute of all strains of the genus [ 22 ]. Considering the FW of 4-week-old seedlings subjected to non-irrigation conditions within the previous two weeks and their phenotype, T. asperellum T140 was selected for further studies.…”

“…Nevertheless, ROS also play a role as signaling molecules in response to stresses. Thus, plants have developed efficient ROS scavenging mechanisms in order to maintain the ROS balance [ 4 , 5 , 6 , 7 ]. Antioxidant enzymes such as superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT) constitute the first line of defense in maintaining basal levels of ROS.…”

“…can induce plant systemic responses to counteract biotic and abiotic stresses, as well as to promote growth [ 18 , 19 ]. Indeed, recent studies have demonstrated that Trichoderma application can enhance wheat tolerance to salinity [ 20 , 21 ], drought [ 6 , 22 , 23 ], and waterlogging [ 24 ]. However, it should not be forgotten that correct strain selection is necessary and is dependent on the interest being pursued [ 22 ].…”

“…However, it should not be forgotten that correct strain selection is necessary and is dependent on the interest being pursued [ 22 ]. It has been suggested that Trichoderma’s production of different phytohormones such as gibberellins (GA), cytokinins (CK), salicylic acid (SA), indole-3-acetic acid (IAA), and abscisic acid (ABA) contributes to balancing the plant phytohormone network and consequently to the signaling processes of the defense responses of plants to abiotic stresses [ 6 , 22 , 25 , 26 ]. Likewise, Trichoderma spp.…”

Root Morphology, Allometric Relations and Rhizosheath of Ancient and Modern Tetraploid Wheats (Triticum durum Desf.) in Response to Inoculation with Trichoderma harzianum T-22

“…Changes in phytohormone levels, in particular auxins and cytokinins have been established to be one of the direct mechanism by which T. harzianum is able to promote tree plant growth and cell wall suberification in the exoderm and endoderm [38,39]. Furthermore, different degrees of Trichoderma strain-dependent in root colonization of wheat have been demonstrated due to a diverse production of eight different phytohormones, including gibberellins, abscisic acid (ABA), salicylic acid (SA), auxin IAA (indole-3-acetic acid), and cytokinins [40]. Trichoderma spp.…”