Abstract
Purpose: To isolate and identify the fungal endophytes of Fagopyrum tataricum and assess their antimicrobial activity.Methods: The fungal isolates were identified according to their morphological characters and internal transcribed spacer (ITS) sequence analysis. Both broth-dilution-colorimetric assay and spore germination test were employed to assess the antimicrobial activity of fungal mycelia extracts.Results: A total of 72 endophytic fungal isolates were successfully obtained from the healthy tissues of F. tataricum. On the basis of their morphological and molecular characteristics, thirteen distinct fungal isolates were identified, and belonged to Alternaria, Bionectria, Botryosphaeria, Fusarium, Guignardia, Nectria, Neonectria, Phomopsis, Pseudocercospora and Verticillium spp. Of these, Pseudocercospora owned the maximum colonization frequency (15.3 %), next for Alternaria (12.5 %) and Neonectria (11.1 %). Through antimicrobial screening assays, six endophytes (Fataf-4, 6, 9, 11, 12 and 15) were active against Bacillus subtilis, Staphylococcus aureus, Agrobacterium tumefaciens, Escherichia coli and Pseudomonas lachrymans, and their minimal inhibitory concentration (MIC) ranged from 0.125 to 2.00 mg/mL. Furthermore, the endophytes, Fataf-9 and Fataf-11, also displayed strong inhibitory activity on the spore germination of F. oxysporum f. sp. vasinfectum and F. oxysporum f. sp. cucumerinum, and their median effective inhibitory concentration (IC50) was 0.356, 0.463, 0.451 and 0.489 mg/mL, respectively.Conclusion: The endophytic fungi of F. tataricum appear to be diverse and promising in their antimicrobial activity, and may represent a potential source of antibiotics for agriculture and/or pharmaceutical applications.Keywords: Endophytic fungi, Fagopyrum tataricum, Diversity, Antimicrobial activity, Antibiotics, Pseudocercospora
Highlights
There is an on-going search for novel antimicrobials which are expected to be high efficiency, low toxicity, eco-friendly and obtainable as the number of drug-resistant pathogens continues to increase [1,2]
The diversity of these fungi associated with the F. tataricum was revealed by colonization frequency (CF)
The results showed that thirteen fungal isolates were identical to the members of eleven different genera, including Alternaria, Bionectria, Botryosphaeria, Fusarium, The internal transcribed spacer (ITS) sequence data of sixteen fungal endophytes from F. tataricum have been successfully submitted to the GenBank database under the accession numbers of KC218445 to KC218460 (Table 1)
Summary
There is an on-going search for novel antimicrobials which are expected to be high efficiency, low toxicity, eco-friendly and obtainable as the number of drug-resistant pathogens continues to increase [1,2]. To provide foundational information for further exploration and utilization of these valuable microorganisms, the aim of present study was to isolate and characterize the endophytic fungal isolates of F. tataricum, and to determine their frequencies of colonization Their potency for the production of antimicrobial components was evaluated further. Five test microorganisms included two gram-positive (Bacillus subtilis ATCC 11562 and Staphylococcus aureus ATCC 6538), and three gram-negative (Agrobacterium tumefaciens ATCC 11158, Escherichia coli ATCC 29425, Pseudomonas lachrymans ATCC 11921) bacteria They were grown in liquid Luria-Bertani (LB) medium (yeast extract 5.0 g/L, peptone 10.0 g/L, NaCl 5.0 g/L, pH 7.0) for 24 h at 30 oC, and the concerntration of bacterial suspension was adjusted to 1 × 106 cfu/mL for detection. The term significant has been used to denote the differences for which p ≤ 0.05
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