An Endophytic Trichoderma Strain Promotes Growth of Its Hosts and Defends Against Pathogen Attack

Abstract

Plants host numerous endophytic microbes which promote plant performance, in particular under stress. A new endophytic fungus was isolated from the leaves of a deciduous wood tree Leucas aspera. Morphological inspection and multilocus phylogeny identified the fungus as a new Trichoderma strain. If applied to Arabidopsis thaliana and Nicotiana attenuata, it mainly colonizes their roots and strongly promotes initial growth of the plants on soil. The fungus grows on high NaCl or mannitol concentrations, and shows predatory capability on the pathogenic fungus Alternaria brassicicola. Colonized Arabidopsis plants tolerate higher salt stress and show lower A. brassicicola spread in roots and shoots, while arbuscular mycorrhiza formation in N. attenuata is not affected by the Trichoderma strain. These beneficial features of the novel Trichoderma strain are important prerequisites for agricultural applications.

Trichoderma and the Plant Heritable Priming Responses

“…Most of the work on Trichoderma –plant interactions has been carried out in root systems. However, it should not be forgotten that many Trichoderma strains live and can be isolated from the aboveground parts of the plant [ 29 ], where they endophytically colonize leaves and stems [ 30 ]. Some strains of Trichoderma are effective in the direct control of pathogens in the phyllosphere, although their mechanism of action seems to be linked more to induced resistance and mycoparasitism than to direct competition [ 31 ].…”

Arabidopsis Restricts Sugar Loss to a Colonizing Trichoderma harzianum Strain by Downregulating SWEET11 and -12 and Upregulation of SUC1 and SWEET2 in the Roots

“…After cold treatment at 4 • C for 48 h, plates were incubated for 10 days at 22 • C under continuous illumination (100 µmol m −2 sec −1 ). The Trichoderma strain was propagated on KM medium (pH 6.5) for a week at 25 • C in the dark, as described previously, and pH changes were monitored by adding 0.004% (w/v) bromocresol purple pH indicator [20]. All experiments with insoluble Pi were performed on National Botanical Research Institute's Pi growth medium (NBRIP) (glucose, 10 g/L: Ca 3 (PO 4 ) 2 , 2.5 g/L; MgCl 2 × 6 H 2 O, 5 g/L; MgSO 4 × 7 H 2 O, 0.25 g/L; KCl, 0.2 g/L; and (NH 4 ) 2 SO 4 , 0.1 g/L), either on plates with 0.3% gelrite or in liquid medium for fungal growth.…”

“…A 5 mm plug of the Trichoderma strain was placed at the center of the cocultivation's plate. Cocultivation was monitored over a period of 10 days at 22 • C under continuous illumination (100 µmol m −2 s −1 ) [20,22].…”

“…We studied the symbiotic interaction of Arabidopsis with a recently characterized Trichoderma harzianum strain [20]. The fungus strongly promotes plant growth on soil and full culture medium [20].…”

“…We studied the symbiotic interaction of Arabidopsis with a recently characterized Trichoderma harzianum strain [20]. The fungus strongly promotes plant growth on soil and full culture medium [20]. However, under Pi limitation, the fungus colonizes Arabidopsis aggressively, shifting the beneficial relationship towards an interaction with no or fewer benefits for the host.…”