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Sundström, Olof, 2020. Choke disease in timothy : seed borne disease and mycotoxins. Second cycle, A2E. Uppsala: SLU, Dept. of Forest Mycology and Plant Pathology

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Abstract

Epichloë spp. and their asexual state, formerly named Neotyphodium, are endophytes of the phylum Ascomycota that are symbionts of cool-season grasses. There has been an estimation that one third of all cool-season grass species all over the world are associated with these endophytes. The endophytes inhabit the above ground part of the plant and can transmit vertically through intercalary growth depending on the host-species interaction. Eventually, infections of the seeds occur through the intercalary growth, or horizontally through dispersion of conidia and ascospores. Sexually reproducing Epichloë spp. are able to produce a light-colored stroma on the leaf sheath of the host. The stroma prevents the inflorescence from emerging and this condition is referred to as choke disease. Epichloë spp. are known for producing alkaloids toxic to vertebrates and invertebrates but can also help the host tolerate various stress factors.

Choke disease is of importance in timothy (Phleum pratense) since it leads to severe yield losses for seed producers due to the choked inflorescences. There is also a concern for mycotoxins toxic to livestock. Epichloë typhina is the only species known to associate with timothy and has never been confirmed to transmit vertically in this host. Given the importance of timothy and the concern from the industry due to the severe outbreaks of choke disease in Sweden 2014 and 2019, the objective of this thesis was to (i) examine possible presence of Epichloë spp. in timothy seeds, (ii) to identify the species of Epichloë present in Swedish timothy, (iii) examine the presence of the mycotoxins ergovaline and lolitrem B in Swedish cool-season grasses and (iv) to better understand the life cycle of Epichloë spp. in timothy.

No sign of Epichloë were to be found in any of the timothy seeds through examination with PCR or microscopy. It was not possible to determine the species of Epichloë through isolation of the fungi or directly from stromata, possibly due to old material. The concentration of ergovaline was below the detection limits in all the samples sent for analysis and lolitrem B could only be detected in four samples, however at low concentrations. The samples sent for analysis were various samples of hay, silage and green mass. Of the 17 samples analyzed, three contained solely timothy and in two of these lolitrem B was found.

The results indicate that Epichloë spp. are not seed borne in timothy, or at least occurs only rarely in seeds. Even though it was not possible to determine the species present in Swedish timothy it can be assumed that the species present is E. typhina since it is the only species reported in timothy. The results from the mycotoxin analysis suggest that there was no obvious risk for livestock to graze on ley infected with Epichloë spp. or to be fed with fodder containing Epichloë spp. in Sweden 2019.

Main title:Choke disease in timothy
Subtitle:seed borne disease and mycotoxins
Authors:Sundström, Olof
Supervisor:Friberg, Hanna
Examiner:Andersson, Björn
Series:UNSPECIFIED
Volume/Sequential designation:UNSPECIFIED
Year of Publication:2020
Level and depth descriptor:Second cycle, A2E
Student's programme affiliation:NY003 Agricultural Programme - Soil/Plant 270 HEC
Supervising department:(S) > Dept. of Forest Mycology and Plant Pathology
Keywords:timothy, Phleum pratense, Epichloë, stroma, stromata, seeds, microscopy, mycotoxins, alkaloids, ergovaline, lolitrem B
URN:NBN:urn:nbn:se:slu:epsilon-s-15909
Permanent URL:
http://urn.kb.se/resolve?urn=urn:nbn:se:slu:epsilon-s-15909
Subjects:Agricultural research
Seed production and processing
Plant diseases
Language:English
Deposited On:18 Aug 2020 08:57
Metadata Last Modified:24 Aug 2020 11:06

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