Endophytic fungi are found in most, if not all, plant species on the planet. They colonise inner plant tissues without causing symptoms of disease, thus providing benefits to the host plant while also benefiting from this interaction. The global concern for the development of more sustainable agriculture has increased in recent years, and research has been performed to decipher ecology and explore the potential of endophytic interactions in plant growth. To date, many studies point to the positive aspects of endophytic colonisation, and in this review, such research is summarised based on the direct (acquisition of nutrients and phytohormone production) and indirect (induced resistance, production of antibiotics and secondary metabolites, production of siderophores and protection for abiotic and biotic stresses) benefits of endophytic colonisation. An in-depth discussion of the mechanisms is also presented.

Background Especially on commodities crops like soybean, maize, cotton, coffee and others, high yields are reached mainly by the intensive use of pesticides and fertilizers. The biological management of crops is a relatively recent concept, and its application has increased expectations about a more sustainable agriculture. The use of fungi as plant bioinoculants has proven to be a useful alternative in this process, and research is deepening on genera and species with some already known potential. In this context, the present study focused on the analysis of the plant growth promotion potential of Purpureocillium lilacinum, Purpureocillium lavendulum and Metarhizium marquandii aiming its use as bioinoculants in maize, bean and soybean. Methods Purpureocillium spp. and M. marquandii strains were isolated from soil samples. They were screened for their ability to solubilize phosphorus (P) and produce indoleacetic acid (IAA) and the most promising strains were tested at greenhouse in maize, bean and soybean plants. Growth promotion parameters including plant height, dry mass and contents of P and nitrogen (N) in the plants and in the rhizospheric soil were assessed. Results Thirty strains were recovered and characterized as Purpureocillium lilacinum (25), Purpureocillium lavendulum (4) and Metarhizium marquandii (1). From the trial for P solubilization and IAA production, seven strains were selected and inoculated in maize, bean and soybean plants. These strains were able to modify in a different way the evaluated parameters involving plant growth in each crop, and some strains distinctly increased the availability of P and N, for the last, an uncommon occurrence involving these fungi. Moreover, the expected changes identified at the in vitro analysis were not necessarily found in planta. In addition, this study is the first to evaluate the effect of the isolated inoculation of these fungi on the growth promotion of maize, bean and soybean plants.

Agriculture is the largest economic sector in the world. The awareness of the current environmental degradation caused by conventional farming practices has allowed the use of entomopathogenic fungi as a biological control technique to become increasingly widespread. Several studies from the laboratory bench to field trials show that fungi can be directly applied or, more recently, can be carried to the target by other biological vectors (i.e., insects), which increases their potential for dispersal and transmission. In addition, studies on the development of formulations have intensified, with the aim to enable their commercialization and reduce costs for the more sustainable management of crops. This review discusses the positive aspects of the use of filamentous fungi in the biological control of pests, specifically in terms of the use of antagonistic fungal plant pathogens and nematophagous fungi.

Fungus-growing ants of the genus Atta are known for their leaf-cutting habit, a lifestyle they have maintained since their 50-million-year-old co-evolution with a mutualistic fungus, cultivated as food. Recent studies have highlighted that, in addition to the mutualistic fungus, nests of ants harbor a great diversity of microbial communities. Such microorganisms include the dematiaceous fungi, which are characterized by their melanized cell walls. In order to contribute to the knowledge of fungal ecology, as well as opportunistic strains that may be dispersed by these social insects, we isolated and identified fungi carried by gynes of Atta capiguara and Atta laevigata, collected from colonies located in Fazenda Santana, Botucatu (São Paulo, Brazil). The isolation was carried out using the oil flotation technique, which is suitable for the growth of black fungi. Inoculated plates were incubated at 25 and 35 °C until black cultures were visible (20-45 days). Isolates were identified based on microscopic and molecular characteristics. Some isolated genera were: Cladophialophora, Cladosporium, Exophiala, Ochroconis, Phaeococcomyces, Phialophora and Penidiella. Hyaline species were also found. The results obtained from this work showed that leaf-cutting gynes may contribute to the dispersal of opportunistic dematiaceous fungi. It is suggested that more attention should be paid to this still unexplored subject.

The use of plant growth-promoting bacteria (PGPB) is a promising alternative method to improve plant efficiency in the utilization of chemical fertilizers, enabling a reduction of fertilizer application on crops. This study aimed to evaluate the potential of ten Bacillus strains (eight B. subtilis, one B. velezensis and one B. amyloliquefaciens) to promote growth in cotton plants under greenhouse conditions. The experiment was performed in a completely randomized design with 11 treatments and five replicates under greenhouse conditions. The parameters related to plant growth from treatments that received the bacterial isolates were compared to the control. The parameters analyzed were shoot dry matter, root dry matter, total dry matter, plant height, nitrogen content and phosphorus content in soil and in plants. The highest root dry matter was 1.24 g for the isolate 263. The total dry matter was 4.0 g for the isolate 248 and 3.54 g for the isolate 290. The highest chlorophyll content was 28 µg/cm2 for the isolate 290. The higher N content in shoot dry matter was 28 g of N for the isolate 290, 26 g for the isolate 248 and 25 g for the isolate 320. The improved P efficiency use was 32% for the isolate 248, 28% for the isolate 188 and 27% for the isolate 274. These results strongly confirm that B. subtilis isolates 248, 290 and 263 may represent a good alternative as plant growth-promoting endophytes to cotton crops, as they positively affected several parameters evaluated, such as root and shoot dry matter and phosphorus content in the soil. In addition, the parameters evaluated can strongly and positively affect plant yield. However, some isolates of B. subtilis did not promote plant growth and most likely failed as bioinoculants. This result shows the importance of properly identifying the isolate for bioinoculation to achieve success in promoting plant growth.