Inoculum potential of Rhizopogon spores increases with time over the first 4 yr of a 99‐yr spore burial experiment

Abstract

Summary• In disturbed or pioneer settings, spores and sclerotia of ectomycorrhizal fungi serve as the necessary inoculum for establishment of ectomycorrhizaldependent trees. Yet, little is known about the persistence of these propagules through time.• Here, live field soil was inoculated with known quantities of basidiospores from four pine-associated species of Rhizopogon; these samples were then buried in retrievable containers, and pine seedling bioassays of serially diluted spore samples were used to measure spore viability.• In the first 4 yr, no evidence of loss of spore viability was found in the four Rhizopogon species tested, but all four species exhibited dormancy in which a maximum of 1-8% of their spores were initially receptive to pine roots. There were some differences between species in overall inoculum potential of their spores, but all species broke dormancy at a statistically similar rate.• This result provides evidence for spore dormancy in a common ectomycorrhizal genus, but it also precludes our ability to estimate the longevity of the spores accurately. Nevertheless these results, coupled with the observed patterns of Rhizopogon spore banks, suggest that at least decade-long durations are likely. As this experiment progresses, the true longevity of the spores will eventually be revealed.

Availability of Ectomycorrhizal Fungi to Black Spruce above the Present Treeline in Eastern Labrador

“…Functional ECMF spore banks (including Laccaria spores) were detected within 40 years of glacial retreat [75] and ECMF spores can act as an inoculum source for several years [37]. In fact, spores of many ECMF species may remain dormant until germination is triggered by the presence of a suitable host plant, such as an establishing seedling [73], [76], [77].…”

“…Dispersal may be by wind [31]), soil fauna [32], or mammals that consume the sporocarps of mycorrhizal fungi [33], [34]. Spore dispersal results in “spore banks” within soils which can accumulate and persist for several years [35]–[37].…”

Population genetics of ectomycorrhizal fungi: from current knowledge to emerging directions

“…Even greater differentiation was detected between populations of Rhizopogon occidentalis, with F ST values reaching 0.26 over 8.5 km (Grubisha et al 2007). Due to their below-ground fruiting, these species likely accumulate large spore banks in soils, from uneaten fruitbodies, that outcompete migrants; moreover, germination potential of the spores seems to increase over 4 y at least, suggesting some type of dormancy (Bruns et al 2008;Nara 2008). Spores of EM species with epigeous fruitbodies dispersed by wind, likely over longer distances, are less persistent (Ishida et al 2008).…”

“…from previous populations to newly settled ones. An exciting long-term experiment was recently set up to assess spore survival in Rhizopogon species over a century (Bruns et al 2008), but more similar efforts will be needed on other model species, e.g. to confirm that wind-dispersed spores persist less efficiently (Ishida et al 2008).…”

What can possibly go wrong?: The risks of introducing soil microorganisms from Antarctica into South America

“…Using fungicide can be an option; nonetheless, its effect seems to be too local for efficient control. Fungi spores are likely to spread quickly from sites of introduction and, once present, spores of some soil mutualists can live decades or hundreds of years in the soil (Bruns et al 2009, Nguyen et al 2012. Given the current lack of effective methods, any problems that might arise from introducing endophytes would present a severe challenge for future control.…”