Evaluation of the phytotoxic effect of extracts from endophytic fungi Colletotrichum dianesei and Xylaria sp. isolated from Palicourea corymbifera (Rubiaceae)

Weison Lima Da Silva,Laísley Martins Lima,Cecilia Veronica Nunez

doi:10.31285/agro.24.423

Abstract

The allelopathic action can be verified by the presence of phytotoxic substances, molecules that are directed to the agribusiness sector. The objective of this study was to evaluate the chemical composition of the methanolic extracts from Colletotrichum dianesei and Xylaria sp., and phytotoxic potential on Lactuca sativa. The fungi were grown in Sabouraud liquid medium supplemented with 0.2% yeast extract, under stirring. The mycelia were subjected to solvent extraction in order of increasing polarity, but methanol extracts were used in this investigation. The allelopathic activity was evaluated at a concentration of 1000 µg/mL in quadruplicate, evaluating: percentage and speed of germination, and growth of lettuce seedlings under laboratory conditions. C. dianesei extract reduced germination percentage by 36% and delayed germination speed by 63.8%, while Xylaria sp. didn't interfere with the germination percentage, it only delayed the germination rate by 43.9%. Root growth was negatively affected in 30.5% and 51.1% under the influence of extracts from Xylaria sp. and C. dianesei, there was also a reduction of 33.1 and 31.8% in the aerial part length, respectively. The thin layer chromatography showed the presence of aromatic substances and terpenes in both extracts, and alkaloids only in C. dianesei extract. The 1H nmr spectra showed signals between 6 and 8.5 ppm (aromatic substances), being relatively more intense for Xylaria sp., signals between 3 and 4 ppm (sugars, showing anomers only for Xylaria sp.) and methyl groups between 0.7 and 1.3 ppm, suggesting terpenes. The results suggest that the fungal species evaluated have phytotoxic potential, and produce terpenes and aromatic substances.

Highlights

Brazil plays an important role in the production and commercialization of food, especially in the cultivation of plant species that are relevant to the country's economy[1]
It was possible to verify a reduction of 36% on germination percentage when the seeds were submitted to the extract of Colletotrichum dianesei (Figure 1)
The germination speed was delayed by 63.8% for C. dianesei, and by 43.9% for Xylaria sp (Figure 2)

Summary

Introduction

Brazil plays an important role in the production and commercialization of food, especially in the cultivation of plant species that are relevant to the country's economy[1]. It is necessary to develop efficient and low-cost technologies capable of minimizing negative environmental impacts. In this sense, research using natural products has stood out, mainly exploring alternative sources in the production of allelochemicals[3]. Endophytic fungi are inserted in this scenario, and have received attention mainly for their competence in the production of secondary metabolites with wide applicability by the industry[4]. Endophytes can increase the competitive capacity of hosts, especially through the production of phytotoxic substances[7]

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Conclusion