Endophytic fungi from the common walnut and their in vitro antagonistic activity against Ophiognomonia leptostyla

• Published in: Biológia Vol. 78; no. 2; pp. 361 - 371
• Main Authors: Yabaneri, Cafer, Sevim, Ali
• Format: Journal Article
• Language: English
• Published: Cham Springer International Publishing 01-02-2023; Springer Nature B.V
• Subjects: Alternaria; Anthracnose; Biological control; Biomedical and Life Sciences; Cell Biology; Control programs; Economic importance; Edible nuts; Endophytes; Fungal diseases; Fungi; Fungicides; Fusarium; Gene sequencing; Genes; Hardwoods; Juglans regia; Life Sciences; Microbiology; Neonectria; Non-ribosomal peptide synthase; Ophiognomonia leptostyla; Original Article; Pathogens; Peptide synthase; Plant Sciences; Plant species; Polyketide synthase; Polyketide synthase I; Roots; Species richness; Walnuts; Zoology; Antifungal genes; Anthracnose; Endophyte; Biological control
• ISSN: 1336-9563; 0006-3088; 1336-9563
• DOI: 10.1007/s11756-022-01218-0

The common (or English) walnut (
Juglans regia
L.) is an economically important hardwood tree species cultivated worldwide for its edible nuts and high-quality wood. However, walnut trees are attacked by many pathogens causing economic damage. Among these pathogens, the most important fungal disease agent of walnut is
Ophiognomonia leptostyla
(Fr.) Sogonov (formerly
Gnomonia leptostyla
(Fr.) Ces. et de Not), which causes walnut anthracnose. In this study, endophytic fungi from various walnuts tissues (leaves, roots, twigs, shoots, fruits, and petioles) were isolated and molecularly identified by ITS gene sequencing. Additionally, the isolated fungi were tested for their in vitro antagonistic potential against
O. leptostyla
. A total of 35 endophytic fungi were isolated and species richness of endophytic fungi in roots was found to be higher than in aboveground organs. The most frequently isolated species was
Fusarium
sp. Seven isolates (
Alternaria
sp. CC-3,
A. chlamydosporigena
CC-8 and CC-9,
Fusarium acuminatum
CC-11, unidentified CC-16,
Neonectria
sp. CC-22 and unidentified CC-44) showed the antagonistic effects on
O. leptostyla
at different rates and the highest inhibition rate was obtained from
Alternaria
sp. CC-3 with 52.5%. Also, the presence of polyketide synthase I-II and non-ribosomal peptide synthase genes (possible antifungal-related genes) was investigated by PCR. From seven isolates showing antagonistic activity, PKS-I gene was detected in 3 isolates (
Alternaria
sp. CC-3,
A. chlamydosporigena
CC-8 and CC-9), PKS-II in one isolate (
F. acuminatum
CC-11), NRPS in two isolates (unidentified CC-16 and
Neonectria
sp. CC-22). None of three genes was detected in one isolate (unidentified CC-44). This is the first study to determine the antagonistic activity of the endophytic fungi isolated from walnuts against
O. leptostyla
. It is thought that the results will be beneficial in the future biological control programs for walnut anthracnose disease.