Effects of the dual inoculation of dark septate endophytes and Trichoderma koningiopsis on blueberry growth and rhizosphere soil microorganisms

A new Schizophyllum commune strain as a potential biocontrol agent against blueberry root rot

In recent years, blueberry root rot has been caused mainly by Fusarium commune, and there is an urgent need for a green and efficient method to control this disease. To date, research on Schizophyllum commune has focused on antioxidant mechanisms, reactive dye degradation, etc., but the mechanism underlying the inhibition of pathogenic microorganisms is still unclear. Here, the control effects of S. commune on F. commune and blueberry root rot were studied using adversarial culture, tissue culture, and greenhouse pot experiments. The results showed that S. commune can dissolve insoluble phosphorus and secrete various extracellular hydrolases. The results of hyphal confrontation and fermentation broth antagonism experiments showed that S. commune had a significant inhibitory effect on F. commune, with inhibition rates of 70.30% and 22.86%, respectively. Microscopy results showed distortion of F. commune hyphae, indicating that S. commune is strongly parasitic. S. commune had a significant growth-promoting effect on blueberry tissue-cultured seedlings. After inoculation with S. commune, inoculation with the pathogenic fungus, or inoculation at a later time, the strain significantly reduced the root rot disease index in the potted blueberry seedlings, with relative control effects of 79.14% and 62.57%, respectively. In addition, S. commune G18 significantly increased the antioxidant enzyme contents in the aboveground and underground parts of potted blueberry seedlings. We can conclude that S. commune is a potential biocontrol agent that can be used to effectively control blueberry root rot caused by F. commune in the field.

Importance of Dark Septate Endophytes in Agriculture in the Face of Climate Change

Climate change is a notable challenge for agriculture as it affects crop productivity and yield. Increases in droughts, salinity, and soil degradation are some of the major consequences of climate change. The use of microorganisms has emerged as an alternative to mitigate the effects of climate change. Among these microorganisms, dark septate endophytes (DSEs) have garnered increasing attention in recent years. Dark septate endophytes have shown a capacity for mitigating and reducing the harmful effects of climate change in agriculture, such as salinity, drought, and the reduced nutrient availability in the soil. Various studies show that their association with plants helps to reduce the harmful effects of abiotic stresses and increases the nutrient availability, enabling the plants to thrive under adverse conditions. In this study, the effect of DSEs and the underlying mechanisms that help plants to develop a higher tolerance to climate change were reviewed.

©Relationship between endophytic fungal diversity and colonization and soil factors of cultured blueberry roots in Guizhou Province, Southwest China

Dark septate endophytes (DSEs) inhabit plant roots and soil in ecosystems and host plants worldwide. DSE colonization is influenced by cultivars, soil factors, and specific habitat conditions. The regular diversity of DSEs in blueberries in Guizhou, China, is still unclear. In this study, four cultivars (Gardenblue, Powderblue, O'Neal, and Legacy) in three areas (Gaopo, Majiang, and Fenggang) in Guizhou were used to identify DSEs by morphological and molecular biological methods and to clarify the relationship between DSE diversity and DSE colonization and soil factors of cultivated blueberries in Guizhou. The DSEs isolated from cultivated blueberry roots in 3 areas in Guizhou Province were different, belonging to 17 genera, and the dominant genera were Penicillium, Phialocephala, and Thozetella. DSEs isolated from Majiang belonged to 12 genera and 16 species, those from Gaopo belonged to 7 genera and 15 species, and those from Fenggang belonged to 5 genera and 7 species. Among the different blueberry varieties, 11 genera were isolated from O'Neal, 12 genera were isolated from Powderblue, 11 genera were isolated from Legacy and 13 genera were isolated from Gardenblue. Coniochaeta is endemic to O'Neal, Chaetomium and Curvularia are endemic to Powderblue, and Thielavia is endemic to Legacy. Correlation analysis showed that DSE diversity was significantly correlated with DSE colonization and soil factors.

Trichoderma spp. promotes ginseng biomass by influencing the soil microbial community

Introduction

Ginseng (Panax ginseng C.A. Meyer) has multiple effects on human health; however, soil degradation seriously affects its yield. Trichoderma spp. play an important role in improving plant biomass by influencing the soil environment. Therefore, it is necessary to screen efficient Trichoderma strains that can increase ginseng biomass and determine their mechanisms.

Methods

Herein, we selected six Trichoderma species (T. brevicompactum, T. velutinum, T. viridescens, T. atroviride, T. koningiopsis, and T. saturnisporum) isolated from ginseng rhizosphere soil, and evaluated their growth promoting effects on ginseng and their influence on the microbiome and chemical attributes of the ginseng rhizosphere soil.

Results

Except for T. saturnisporum (F), compared with the control, the other five species increased ginseng biomass. In terms of chemical properties, the pH value, available potassium content, and available phosphorus content in the ginseng rhizosphere soil increased by 1.16-5.85%, 0.16-14.03%, and 3.92-38.64%, respectively, after root irrigation with spores of Trichoderma species. For the soil microbiome, fungal Chao1 and Ace richness indices decreased. Application of Trichoderma enhanced the relative level of Proteobacteria, but reduced the relative level of Ascomycota. At the genus level, application of Trichoderma enhanced the relative levels of Sphingomonas, Blastomonas, and Trichoderma, but reduced the relative level of Fusarium. Available K and available P were the most important elements that affected the structure of the bacterial community, while total K was the most influential element for the structure of the fungal community structure.

Conclusion

The results indicated that the application of Trichoderma spp. could increase soil nutrients and regulate the structure and composition of the soil microbial community, thereby enhancing the biomass of ginseng. The results will provide guidance for soil improvement in ginseng cultivation.