Diverse Xylaria in the Ecuadorian Amazon and their mode of wood degradation

• Published in: Botanical studies Vol. 64; no. 1; p. 30
• Main Authors: Rajtar, Nickolas N., Kielsmeier-Cook, Joshua C., Held, Benjamin W., Toapanta-Alban, Cristina E., Ordonez, Maria E., Barnes, Charles W., Blanchette, Robert A.
• Format: Journal Article
• Language: English
• Published: Singapore Springer Nature Singapore 25-10-2023; Springer Nature B.V; SpringerOpen
• Subjects: Balsa; Biomass; Biomedical and Life Sciences; Decay; Decay fungi; Degradation; Ecology; Ecuador; Electron micrographs; Fruit bodies; Fungi; Life Sciences; National parks; Nutrient cycles; Original; Original Article; Plant Genetics and Genomics; Plant Sciences; Rainforests; Soft rot; Spacer region; Species; Taxonomic and ecological studies on Ascomycota; Tropical rainforest; Variance analysis; with emphasis on xylariaceous fungi; Wood; Wood decay; Xylaria; Xylariales; Ecuador; Fungi; Ecuador; Wood decay; Xylariales; Tropical rainforest
• ISSN: 1999-3110; 1817-406X; 1999-3110
• DOI: 10.1186/s40529-023-00403-x

Background
Xylaria
is a diverse and ecologically important genus in the Ascomycota. This paper describes the xylariaceous fungi present in an Ecuadorian Amazon Rainforest and investigates the decay potential of selected
Xylaria
species. Fungi were collected at Yasuní National Park, Ecuador during two collection trips to a single hectare plot divided into a 10-m by 10-m grid, providing 121 collection points. All
Xylaria
fruiting bodies found within a 1.2-m radius of each grid point were collected. Dried fruiting bodies were used for culturing and the internal transcribed spacer region was sequenced to identify
Xylaria
samples to species level. Agar microcosms were used to assess the decay potential of three selected species, two unknown species referred to as
Xylaria
1 and
Xylaria
2 and
Xylaria curta
, on four different types of wood from trees growing in Ecuador including balsa (
Ochroma pyramidale
), melina (
Gmelina arborea
), saman (
Samanea saman
), and moral (
Chlorophora tinctoria
). ANOVA and post-hoc comparisons were used to test for differences in biomass lost between wood blocks inoculated with
Xylaria
and uninoculated control blocks. Scanning electron micrographs of transverse sections of each wood and assay fungus were used to assess the type of degradation present.
Results
210
Xylaria
collections were sequenced, with 106 collections belonging to 60 taxa that were unknown species, all with less than 97% match to NCBI reference sequences.
Xylaria
with sequence matches of 97% or greater included
X
. aff.
comosa
(28 isolates),
X. cuneata
(9 isolates)
X. curta
and
X
.
oligotoma
(7 isolates), and
X
.
apiculta
(6 isolates)., All
Xylaria
species tested were able to cause type 1 or type 2 soft rot degradation in the four wood types and significant biomass loss was observed compared to the uninoculated controls. Balsa and melina woods had the greatest amount of biomass loss, with as much as 60% and 25% lost, respectively, compared to the controls.
Conclusions
X
ylaria
species were found in extraordinary abundance in the Ecuadorian rainforest studied. Our study demonstrated that the
Xylaria
species tested can cause a soft rot type of wood decay and with the significant amount of biomass loss that occurred within a short incubation time, it indicates these fungi likely play a significant role in nutrient cycling in the Amazonian rainforest.