Plant-associated Fungi: Methods for Taxonomy, Diversity, and Bioactive Secondary Metabolite Bioprospecting.

Plants harbor a large reservoir of fungal diversity, encompassing endophytic, epiphytic, phytopathogenic, and rhizosphere-associated fungi. Despite this diversity, relatively few fungal species have been characterized as sources of bioactive secondary metabolites. The role of secondary metabolites is still not fully understood; however, it is suggested that these metabolites play important roles in defense mechanisms and fungal interactions with other organisms. Hence, fungal secondary metabolites have potential biotechnological applications as prototype molecules for the development of therapeutic drugs. In this chapter, we describe the main methods used for routine fungi isolation, production of crude fungal extracts, and chemical characterization of bioactive compounds. In addition, explicative notes about the steps described are provided to explore the diversity of the endophytic, phytopathogenic, epiphytic, and rhizosphere fungi and to evaluate the biotechnological potential of each group.

Endophytic fungus diversity in soybean plants submitted to conditions of elevated atmospheric CO2 and temperature.

Global climatic changes can have drastic impacts on plant species, including severe consequences for the agricultural species productivity. Many of these species present important mutualisms with endophytic fungi that positively influence their performance. The present study evaluated whether the increases in CO2 and temperature predicted for the year 2100 may cause changes in foliar carbon (C) and nitrogen (N) concentrations in soybean (Glycine max) and, consequently, the interactions with its endophytic fungi. The effects of elevated CO2 and temperature were evaluated in four treatments in open-top chambers: (i) control, (ii) increased temperature, (iii) increased CO2, and (iv) increased CO2 and temperature. Increased atmospheric CO2 resulted in decreased foliar N concentration, while increased temperature increased it. A total of 16 taxa of endophytic fungi were identified based on sequencing internal transcribed spacer regions of rRNA subunits. Increased atmospheric CO2 and temperature were observed to potentially modify the endophytic mycobiota of soybean plants. The results suggest that the fungi species substitution is a consequence of changes in foliar N concentration and C/N ratio. Predicted climatic changes shall affect the relationships between plant and endophytes, which in turn, will affect the performance and resistance of soybean, one of the most important crops in the world.

Penicillium citrinum and Penicillium mallochii: New phytopathogens of orange fruit and their control using chitosan.

The antimicrobial action of chitosan against several phytopathogens in agriculture has been tested, including Penicillium digitatum, which is the major pathogen that causes postharvest decay of oranges. However, the biopolymer action has not been tested against other fungi that are capable of developing molds in orange fruit. This study have demonstrated that chitosan is able to inhibit the growth in vitro and in vivo of two Penicillium species, which were isolated from decay oranges fruit and identified as Penicillium citrinum and Penicillium mallochii, using molecular methods. This is the first report of P. mallochii acting as an orange phytopathogen. The commercial chitosan with higher molecular weight demonstrated a reduction in the disease incidence of 50-70 % for the inoculum P. citrinum and of 40 % for the inoculum P. mallochii for the in vivo experiments. The data obtained opens interesting alternative options to synthetic fungicide to prevent orange decay caused by the potential phytopathogenic species of Penicillium here identified.