Could Trichoderma Be a Plant Pathogen? Successful Root Colonization

<i>Trichoderma spp.</i> strains: growth and interaction at different temperatures

The paper examines the growth of Trichoderma spp. strains and their interaction at different temperatures. Trichoderma spp. is a genus of microscopic ascomycetes; these fungi belong to different ecosystems and are found in soil (rhizosphere). The study aims to analyze and compare the characteristics pertaining to the growth of Trichoderma species and the interaction between them. The experiments used the following media: a Czapek medium and a medium simulating plant root exudates (Cucumis sativus). The growth rate of Trichoderma spp. strains was determined at different temperatures. The use of a medium containing plant exudate models provided a different growth rate as compared to that obtained when using a rich growth medium; some variations in the macromorphology of colonies were also observed. The growth of Trichoderma longibrachiatum F2124 and Trichoderma viride F2001 strains was detected at 9 °С on the Czapek medium, while only the Trichoderma longibrachiatum F2124 strain was observed to grow on the medium simulating exudates. A significant growth inhibition was noted at 40 °С for all strains, except for Trichoderma longibrachiatum species. No colony growth was observed at 50 °С. All the strains grew within the temperature range of 12 to 28 °С. It was assumed that Trichoderma species growing in various media may interact differently with each other. Interaction between the three strains of Trichoderma spp. was examined via the surface culture method under different temperature conditions. The study found no significant differences in the interaction between the Trichoderma species.

Fungal Inhibition of Agricultural Soil Pathogen Stimulated by Nitrogen-Reducing Fertilization

Plant health is the fundamental of agricultural production, which is threatened by plant pathogens severely. The previous studies exhibited the effects of different pathogen control strategies (physical, chemical, and microbial methods), which resulted from bringing in exogenous additives, on microbial community structures and functions. Nevertheless, few studies focused on the potential inhibitory abilities of native microbial community in the soil, which could be activated or enhanced by different fertilization strategies. In this study, three plant diseases (TMV, TBS, and TBW) of tobacco, fungal community of tobacco rhizosphere soil, and the correlation between them were researched. The results showed that nitrogen-reducing fertilization strategies could significantly decrease the occurrence rate and the disease index of three tobacco diseases. The results of bioinformatics analyses revealed that the fungal communities of different treatments could differentiate the nitrogen-reducing fertilization group and the control group (CK). Furthermore, key genera which were responsible for the variation of fungal community were explored by LEfSe analysis. For instance, Tausonia and Trichocladium increased, while Naganishia and Fusicolla decreased under nitrogen-reducing fertilization conditions. Additionally, the correlation between tobacco diseases and key genera was verified using the Mantel test. Moreover, the causal relationship between key genera and tobacco diseases was deeply explored by PLS–PM analysis. These findings provide a theoretical basis for a nitrogen-reducing fertilization strategy against tobacco diseases without exogenous additives and make contributions to revealing the microbial mechanism of native-valued fungal key taxa against tobacco diseases, which could be stimulated by agricultural fertilization management.

Trichoderma-Based Biopreparation with Prebiotics Supplementation for the Naturalization of Raspberry Plant Rhizosphere

The number of raspberry plants dying from a sudden outbreak of gray mold, verticillium wilt, anthracnosis, and phytophthora infection has increased in recent times, leading to crop failure. The plants suffer tissue collapse and black roots, symptoms similar to a Botrytis-Verticillium-Colletotrichum-Phytophthora disease complex. A sizeable number of fungal isolates were acquired from the root and rhizosphere samples of wild raspberries from different locations. Subsequent in vitro tests revealed that a core consortium of 11 isolates of selected Trichoderma spp. was the most essential element for reducing in phytopathogen expansion. For this purpose, isolates were characterized by the efficiency of their antagonistic properties against Botrytis, Verticillium, Colletotrichum and Phytophthora isolates and with hydrolytic properties accelerating the decomposition of organic matter in the soil and thus making nutrients available to plants. Prebiotic additive supplementation with a mixture of adonitol, arabitol, erythritol, mannitol, sorbitol, and adenosine was proven in a laboratory experiment to be efficient in stimulating the growth of Trichoderma isolates. Through an in vivo pathosystem experiment, different raspberry naturalization-protection strategies (root inoculations and watering with native Trichoderma isolates, applied separately or simultaneously) were tested under controlled phytotron conditions. The experimental application of phytopathogens attenuated raspberry plant and soil properties, while Trichoderma consortium incorporation exhibited a certain trend of improving these features in terms of a short-term response, depending on the pathosystem and naturalization strategy. What is more, a laboratory-scale development of a biopreparation for the naturalization of the raspberry rhizosphere based on the Trichoderma consortium was proposed in the context of two application scenarios. The first was a ready-to-use formulation to be introduced while planting (pellets, gel). The second was a variant to be applied with naturalizing watering (soluble powder).