Colonization of Vitis vinifera L. by the Endophyte Trichoderma sp. Strain T154: Biocontrol Activity Against Phaeoacremonium minimum

Abstract

Trichoderma strains used in biological control products usually exhibit high efficiency in the control of plant diseases. However, their behavior under field conditions is difficult to predict. In addition, the potential of indigenous strains has been poorly assayed as well as their possible behavior as endophytes. Hence, niche colonization is a key feature for an effective protection. In this study, we aimed to: (i) explore the possibility of using a new Trichoderma strain isolated from vine to control pathogens, (ii) study the in planta interaction with the pathogen Phaeoacremonium minimum W. Gams, Crous, M.J. Wingf. & L. Mugnai (formerly Phaeoacremonium aleophilum), a pioneer fungus involved in Grapevine Trunk Diseases (GTDs) such as esca. For this purpose, fluorescently tagged Trichoderma sp. T154 and a P. minimum strain were used for scanning electron microscopy and confocal scanning laser microscopy analyses. Data showed that the Trichoderma strain is able to colonize plants up to 12 weeks post inoculation and is located in xylem, fibers, as well as in parenchymatic tissues inside the wood. The beneficial fungus reduced colonization of the esca-related pathogen colonizing the same niches. The main observed mechanism involved in biocontrol of Trichoderma against the esca pathogen was spore adhesion, niche exclusion and only few typical hypha coiling was found between Trichoderma and the pathogen. These results suggest that the Trichoderma strain has potential for reducing the colonization of Phaeoacremonium minimum and thus, an inoculation of this biological control agent can protect the plant by limiting the development of GTD, and the strain can behave as an endophyte.

The Influence of Temperature on the Growth, Sporulation, Colonization, and Survival of Trichoderma spp. in Grapevine Pruning Wounds

“…However, not all T. harzianum strains can be described as efficient BCAs. Previously, T154 has been tested against P. minimum as an effective BCA that uses niche exclusion mechanisms for biocontrol [47], and T214 was shown to have a significant antifungal activity in our case (data not shown). These two strains belong to the clade HV that possesses a complex taxonomy and has not been fully identified due to its coexistence and interaction with all these organisms that together create this clade and have a lack of strict genetic borders between them [68].…”

“…Kühn [86]. Furthermore, native Trichoderma were able to colonize pruning wounds against P. minimum [47]. However, on the contrary, studies carried out with some commercial Trichoderma-based bioproducts concluded that they did not show a good plant colonization ability under the selected conditions [28].…”

“…Its persistence over grapevine wounds was significantly higher at 89.58% when sprayed with T154 at 2 × 10 −6 CFU/mL, in comparison to 70.31% for T071 at the same concentration of spores. Niche exclusion was described as one of the mechanisms used by T154 [47] in order to biocontrol P. minimum and it could be a reason for its successful colonization. Moreover, its capacity to produce a greater number of spores and its mycoparasitic activity would point to this strain as a suitable BCA [71].…”

“…T065 and T214 were selected based on their high potential to produce secondary metabolites; T214 showed a remarkable mycoparasitic activity against the pathogenic fungus Phaeoacremonium minimum (unpublished data); Trichoderma T071 is effective against the Xylotrechus arvicola insect pest [46]; and Trichoderma sp. T154 also possesses significant mycoparasitic activity against P. minimum [47].…”

“…Trichoderma T154 was classified into Clade Harzianum/Virens (HV) [47] and Trichoderma T071 was assigned to Section Trichoderma (ST) [46]. The criteria followed for this assessment was applied according to Kubicek et al, 2019 [48].…”