Longevity of light- and dark-colored basidiospores from saprotrophic mushroom-forming fungi

Fungi can produce resistant propagules that may last for decades. Basidiospores from ectomycorrhizal fungi had been experimentally shown to last for at least 6 yr, but there are few reports on the longevity of saprotrophic members of mushroom-forming fungi. Here, the author shows evidence of spore longevity of these fungi by collecting, drying, storing, and germinating these spores over time. Results showed that dark-colored spores have a much-extended longevity as compared to light-colored spores. Dark-colored spores of some species are viable to at least 2.8 yr, whereas light-colored spores are generally viable for a much shorter period of time. The author proposes that mushroom-forming basidiomycete fungi employ two different ecological strategies: one with extended longevity that allows for long-distance dispersal, and the other takes advantage of optimal conditions that support both mushroom formation, basidiospore dispersal, and germination locally.

The persistence and germination of fern spores in fire-prone, semi-arid environments

In addition to population regeneration, the spore phase provides ferns with a capacity for dispersal through space and time (if spores are able to survive for long periods), and buffers their populations against environmental extremes. Inhabiting dry and fire-prone environments provides specific challenges to ferns, and the traits of fern spores in relation to these challenges are not well understood. Their shallow, dense and fibrous root networks mean that the loss or establishment of fern populations in disturbed ecosystems may influence soil stability, and indicate a keystone role in ecosystem function and ecological restoration. Here, we examine the requirements for, and limits of, spore persistence and germination of three Cheilanthes Syn.Fil. (Pteridaceae) species, namely, optimal conditions for spore germination and prothallial growth, sensitivity to temperature extremes and spore longevity. Viability of fresh spores was assessed following exposure to temperature extremes (–20 to 250°C) or after incubation at a range of temperatures (10−35°C) and in light or dark conditions. Viability of spores from herbarium voucher specimens was also assessed, covering 3–65 years of storage. Maximal germination occurred among spores incubated between 20°C and 30°C in light. Further temperature variation within this range resulted in a ×10 difference in prothallial size. Germination was unaffected by 10 min of exposure to temperatures up to 100°C, but was reduced after exposure to temperatures of −20°C and 110°C. Germination of herbarium-stored spores demonstrated longevity of up to 15 years. This longevity, combined with high spore density in field soils (including at depth to at least 10 cm), very high germination under ideal conditions, and microscopic size, describes a disturbance-mediated propagule persistence strategy. Spores are non-persisting and will germinate if exposed to light and water, but do persist if buried. Germinable spore can be found 5 cm below the soil surface, and can persist for at least 15 years, but the light requirement for germination means that persistent spores can achieve germination only if exhumed. Elucidating these traits reveals a unique pathway for plant persistence, and contributes to the development of the restoration capacity of arid-environment ferns.

Fast Real-Time PCR assay for detection of Tetramicra brevifilum in cultured turbot

SUMMARYGlobal aquaculture production of turbot has rapidly increased worldwide in the last decade and it is expected to have even bigger growth in the next years due to new farms operating. The losses caused by pathogen infections have grown at the same time as the production of this species. Parasitological infections are among the main relevant pathologies associated with its culture and produce serious losses in aquaculture, reduce the growth rate in fish and may lead to unmarketable fish due to skeletal muscle abnormalities in cases with high intensity of infection. The microsporidian parasite Tetramicra brevifilum causes severe infections and generates major losses in farmed turbot. Infections are difficult to control due to spore longevity and its direct transmission. To facilitate the infection management, an effective tool for fast detection and identification of T. brevifilum is needed. This study provides a molecular methodology of fast Real-Time PCR for T. brevifilum detection to the aquaculture industry, useful for routine control of T. brevifilum at turbot farms. The method is characterized by its high specificity and sensitivity, and it can be applied to cultured turbot for parasite detection regardless of the life-cycle stage of the pathogen or the infection intensity.

Survival of Endocronartium harknessii teliospores in a simulated airborne state

The effects of temperature and relative humidity (RH) on the survival of Endocronartium harknessii teliospores and the longevity of these spores out of doors during daylight hours were studied. In one experiment, fresh and liquid-nitrogen-stored spores of E. harknessii were impacted onto spider webs or plastic threads and incubated in darkness at temperatures of 6, 15, and 24 °C and RHs of 39 and 98%. Survival was measured after 1, 2, 4, 8, and 16 days. Spore longevity decreased with increasing temperature and was lower at 98 than at 39% RH. In a second experiment, spores were impacted onto spider webs and placed out of doors on clear days. Viability decreased linearly with time and averaged 33% after 12 h. The data suggest that E. harknessii has relatively good ability to survive in an airborne state and thus would have considerable potential for long distance spread.

Survival of Cochliobolus sativus conidia in pure culture and in natural soil at different relative humidities

Conidia of Cochliobolus sativus cultured on sterile wheat straw were nearly 100% germinable after 52 months when maintained at relative humidity of 50% or lower. At higher relative humidity, spore longevity was much reduced. Increased temperature decreased spore longevity. Comparable results were obtained in natural soil.