Mycorrhizal vs saprotrophic status of fungi: the isotopic evidence

Abstract

Summary• Relative abundances of carbon and nitrogen isotopes in fungal sporocarps are useful in assessing mycorrhizal or saprotrophic status, and might provide insights into the evolutionary history of these traits.• Sporocarps of known mycorrhizal or saprotrophic genera were collected at Woods Creek, OR, USA, and isotopically compared with foliage, litter, soils and wood collected from the same site. Possible trophic strategies were then isotopically assessed in archived specimens of the Pezizales of known molecular phylogeny from the western United States.• At Woods Creek, mycorrhizal fungi were 3.5‰ ± 0.6‰ depleted in δ 13 C and 5.7‰ ± 0.4‰ enriched in δ 15 N compared with saprotrophic fungi. By contrast, fungi from four genera of uncertain mycorrhizal status ( Clavulina , Helvella , Otidia , and Ramaria ) were only 0.4‰ ± 0.4‰ enriched in δ 13 C and 1.2‰ ± 1.1‰ depleted in δ 15 N relative to mycorrhizal fungi.• In archived samples, the δ 13 C measurements appeared to be a better indicator of trophic strategy than δ 15 N measurements. The δ 13 C measurements suggested that mycorrhizal or saprotrophic status was conserved within families of the Pezizales (as determined by molecular phylogeny), with the Helvellaceae and Tuberaceae mycorrhizal and Discinaceae and Morchellaceae being largely saprotrophic.

Stratégie saprophyte ou symbiotique durant le développement d’ascocarpes de truffes dans une truffière à chêne vert. Une réponse basée sur l’abondance naturelle du 13C et du 15N

“…As reported by several authors (Gebauer and Taylor, 1999;Henn and Chapela, 2001;Hobbie et al, 1999Hobbie et al, , 2001Högberg, 1997;Kohzu et al, 1999;Taylor et al, 2003, Trudell et al, 2004Zeller et al, 2007), δ 13 C values differed between sporophores of saprotrophic and ectomycorrhizal fungi. Sporophores of the two saprotrophic fungi from the Châteauvert site showed a 13 C enrichment compared to their substrates.…”

“…The three Tuber species displayed a high δ 15 N value (9.3 to 10.4% ). Hobbie et al, (2001) also found for T. gibbosum, a North American truffle, high δ 15 N values (12.0 to 16.6% ). In the Châteauvert site, the amplitude of δ 15 N variation among ectomycorrhizal sporophores was similar to the amplitude observed in the Breuil forest (-1.0% to 10.2% ).…”

“…Natural abundance of 13 C and 15 N has frequently been used to study fungal sources of carbon and nitrogen (Hobbie et al, 2001). Gebauer and Dietrich (1993) found that positive 15 N values of fungal sporophores indicated that fungi can utilize organic soil nitrogen.…”

A review on research advances, issues, and perspectives of morels

“…Stark et al (2009) speculated morels were associated with orchids, based on evidence obtained through PCR-amplification directly from root-extracted DNA and cloning of the PCR products. Hobbie et al (2001) and Li et al (2013) assessed the trophic status of morels by examining the relative abundance of stable isotopes. Hobbie et al (2001) suggested that morels were largely saprophytic, but Li et al (2013) suggested that morels with black pilei were saprophytic and those with yellow pilei were mycorrhizal.…”

“…Hobbie et al (2001) and Li et al (2013) assessed the trophic status of morels by examining the relative abundance of stable isotopes. Hobbie et al (2001) suggested that morels were largely saprophytic, but Li et al (2013) suggested that morels with black pilei were saprophytic and those with yellow pilei were mycorrhizal. Baynes et al (2012) detected Morchella as an endophyte in the aboveground stem tissue of cheatgrass and reported that M. sextelata M. Kuo and M. snyderi M. Kuo & Methven could infect cheatgrass roots.…”