Spore rain in relation to regional sources and beyond

While patterns of spore dispersal from single sources at short distances are fairly well known, information about ‘spore rain’ from numerous sources and at larger spatial scales is generally lacking. In this study, I sampled spore rain using a novel method consisting of 0.25–0.5 m² cotton cloth traps at nine sites in the boreo‐nemoral vegetation zone in eastern Sweden during two seasons, using Sphagnum spores as a model. Traps were located in various landscapes (mainland, islands). Additional trapping was done in an arctic area (Svalbard) without spore production. Spore densities were tested against distance from the nearest source and area of sources (open peatlands) within different radii around each site (5, 10, 20, 50, 100, 200, 300, 400 km). The cloth method appeared reliable when accounting for precipitation losses, retaining approximately 20–60% of the spores under the recorded amounts of precipitation. Estimated spore densities ranged from 6 million m^?2 and season within a large area source, via regional deposition of 50 000–240 000 spores m^?2, down to 1000 m^?2 at Svalbard. Spore rain for all sites was strongly related to distance from the nearest source, but when excluding samples taken within a source peatland, the amount of sources within 200 km was most important. Spores were larger at isolated island sites, indicating that a higher proportion originated from distant, humid areas. Immense amounts of Sphagnum spores are dispersed across regional distances annually in boreal areas, explaining the success of the genus to colonise nutrient poor wetlands. The detectable deposition at Svalbard indicates that about 1% of the regional spore rain has a trans‐ or intercontinental origin. The regional spore rain, originating from numerous sources in the landscape, is probably valid for most organisms with small diaspores and provides a useful insight in ecology, habitat restoration and conservation planning.     

Production of diaspores at the landscape level regulates local colonization: an experiment with a spore‐dispersed moss

Effective dispersal is crucial to species inhabiting transient substrates in order for them to be able to persist in a landscape. Bryophytes, pteridophytes, lichens and fungi all have wind‐dispersed small diaspores and can be efficiently dispersed if their diaspores reach air masses above canopy height. However, empirical data on dispersal over landscape scales are scarce. We investigated how the colonization of an acrocarpous clay‐inhabiting pioneer moss, Discelium nudum, varied between sites that differed in connectivity to potential dispersal sources at spatial scales from 1 to 20 km in a region in northern Sweden. We recorded the colonization on ?25 introduced clay heaps at each of 14 experimental sites some months after the dispersal period. The colonization rate ranged from 0–82% and had a statistically significant relationship with a proxy for potential habitats (amount of clay‐dominated soil) in a buffer of 20 km radius surrounding the experimental sites (and also weakly with the amount of substrate in a 10 km buffer). There were no significant relationships between colonization rate and connectivity at smaller scales (1 and 5 km). We made a rough estimate of the number of spores available for dispersal in a landscape, given the amount of clay‐dominated soil, by recording the number of Discelium nudum colonies in two 25 × 25 km landscapes. The estimated available spore numbers in the different 20 km buffers were of the same order of magnitude as the deposition densities at the experimental sites calculated from the colonization rates. The results suggest that the spores of species with scattered occurrences and small diaspores (25 μm) in open landscapes can be deposited over extensive areas, at rates high enough to drive colonization patterns. This also implies that regional connectivity may be more important than local connectivity for these kinds of species.     

Wind Dispersal of Alternaria alternata, a Cause of Leaf Blight of Cotton

Introducing Alternaria alternata, the cause of blight disease of cotton plants, into a field of young healthy plants growing in rows cross-wind, yielded disease foci which were spread downwind up to 7 m from the infection sources. Only light disease incidence was found in the remainder of the field. When the disease was introduced into a field of mature cotton plants grown in rows cross-wind, randomly scattered disease foci occurred. In mature plantations where rows were parallel to the average wind direction, only limited size disease foci developed downwind, up to 16 m from the source. These foci did not developed further during the season. The number of air-borne spores of A. alternata was significantly increased by the presence of diseased cotton plants, being highest close to the diseased plants. The spores were transferred to a distance of at least 20 m. However, the number of air-borne spores significantly decreased 6 m from the infection source. Periodical trapping of air-borne spores of A. alternata in a cotton growing region for 2 years, revealed that their air dispersal is local, probably at the field level. A. alternata in a cotton growing region for 2 years, revealed that their air dispersal is local, probably at the field level. A. alternata air-borne spores were also trapped in rather low numbers regardless of the presence of infected cotton plants. However, the number of the air-borne spores trapped was dependent mainly on the average wind direction and on the Alternaria blight epidemics occurring in the fields twice a year. It is suggested that A. alternata spores are transferred by wind for short distances but are constantly present in small numbers in the atmosphere throughout the whole year. The two peaks recorded for the number of spores present in the air above cotton crops correlate with the annual two outbreaks of Alternaria blight epidemics. In addition, both wind and plant row direction affect disease development in the fields.     

Pressure effects on<Emphasis Type="Italic"> Clostridium</Emphasis> strains isolated from a cold deep-sea environment

Three Clostridium strains were isolated from deep-sea sediments collected at a depth of 6.3–7.3 km in the Japan Trench. Physiological characterization and 16S rDNA analysis revealed that the three isolates were all closely related to Clostridium bifermentans. The spores of all three isolates were resistant to inactivation at high pressure and low temperature. However, despite the fact that the vegetative cells were halotolerant and eurythermal they did not appear to be adapted for growth or viability under the conditions prevailing in the deep-sea sediments from which they were obtained. The results suggest that the isolates had survived as spores in the deep-sea sediments and that the marine benthos could be a source of clostridia originating in other environments.Communicated by K. Horikoshi     

Fern spore and pollen airspora profile of Singapore

Monitoring atmospheric fern spore and pollen loads in Singapore was initiated in June 1990. Aside from the more numerous fungal spores, fern spores and pollen grains made up 6.2–8.6% and 4.4–5.4% of the total airspora sampled, respectively. The most frequently encountered fern spores, in descending order, were those of Nephrolepis auriculata, Dicranopteris linearis, Stenochlaena palustris, Asplenium nidus, Pteridium aquilinum, and Dicranopteris curranii. For pollen grains, the most frequently encountered, in descending order, were Elaeis guineensis, Casuarina equisetifolia, Acacia auriculiformis, Kyllingia polyphylla, Podocarpus, and Poaceae pollen grains. Seasonal patterns for individual fern spore or pollen types were discernible despite the relatively uniform tropical climate in Singapore. The fern spore and pollen calendar for the period 1991–1995 was compared to that of 2005–2006 as a follow-up study to keep abreast with the rapidly changing landscape of Singapore. Diurnal patterns showing a late morning to afternoon peak period were seen in fern spores, while the peak period was in the morning for pollen types studied with the exception to oil palm pollen. Additionally, association between fern spore and pollen counts and local meteorological conditions were also analyzed and found to be highly correlated. This study has thus identified the fern spores and pollen airspora components, and determined the calendars, as well as diurnal profiles of the Singapore airspora and provides invaluable information for allergy studies by highlighting the trigger sources present in the environment.     

Aeroallergens in northern and southern provinces of Thailand

An aeroallergen survey in two provinces, Chiangmai in the northern and Songkhla in the southern part of Thailand which are 1 500 km apart, was done in 1986 and 1987 using a rotorod sampler. The five most common pollen types and mold spores were: Chiangmai: Mold spores: Cladosporium, rust, Fusarium, Nigrospora, 1-celled spore. Pollen grains: Mimosa, wild grasses, Urticaceae, Cyperaceae, tetrad pollen. Songkhla: Mold spores: Cladosporium, rust, Nigrospora, Papularia, 1-celled spore. Pollen grains: Casuarina, Mimosa, Urticaceae, Cyperaceae, wild grass. There were definite differences in the amount and frequency of occurrences of aeroallergens between these two provinces. Furthermore, some specific pollen and mold spores, such as tetrads and Mimosa pollen, were found only in Chiangmai, and Casuarina pollen and Papularia spores only in Songkhla. These findings might be caused by the differences in geography, plantation and meteorological data.     

Circadian periodicity of airborne pollen and spores; significance of sampling height

Summary The circadian periodicity of the five allergologically most important pollen types in S. Finland and two different spore types were studied at two sites, about 200 meters apart: one Burkard sampler situated on a roof at a height of 15 meters and the other on a garden lawn at ground level. The circadian rhythms of pollen released close to the ground (herb pollen) did not correlate at the two sampling heights used. Variations in pollen from high sources (trees) were significantly correlated at the two heights used. The circadian rhythms of spores from low source distant from the sampling sites (Suillus as an example of forest fungi) were not always correlated; instead, spores with sources at different heights (Cladosporium as an example) had similar circadian periodicity not depending on the sampling level. It was shown that, when studying circadian rhythms of atmospheric particles, the sampling height used is often of great importance. Circadian rhythms of the same pollen and spore types for ten years at the higher sampling site are presented for long-term comparison.     

Effects of meteorological factors on airborne bracken (<Emphasis Type="Italic">Pteridium aquilinum</Emphasis> (L.) Kuhn.) spores in Salamanca (middle-west Spain)

Temporal variation of airborne bracken (Pteridium aquilinum) spores concentration in Salamanca during 10 years from January 1998 to December 2007 were studied by using a Burkard spore trap, and correlations with some meteorological parameters were analyzed. The number of spores that were counted was very low, due probably to the distance between the spore trap and the main bracken populations which were located 70 km away from the city. Long-range transport caused by winds coming from the Second Quadrant (IIQ) is supposed to be responsible for the appearance of bracken spores in Salamanca. The season period from August to late October shows the most intense spore dispersal process, with an early morning distribution along the day. Years 2002 and 2007 with a low quantity of airborne spores were also characterized by low mean temperatures, always under 18°C from May to June. Daily spore concentration shows positive correlation with temperature and sun hours but negative with IVQ winds and with relative humidity. No correlation between daily spore concentration and rainfall was found. Also, a positive correlation between number of spores and IIQ winds was observed during the main spore season (MSS) and prepeak period (PRE).     

A comparison of two methods and different media for isolatingFrankia from Casuarina root nodules

Four species of Casuarina were raised in the glasshouse and inoculated with nodules collected from nine different geographical areas within Australia. Isolations ofFrankia were attempted from 10 of the Casuarina-Frankia nodule combinations using two methods, a nodule dissection and a filtration method. With both techniquesFrankia isolates were obtained from four of the 10Frankia sources. Spores were not observed in sections of nodules from the four sources from whichFrankia was isolated, whereas spores were observed in the remaining six nodule sources. For selected nodule sources a range of isolation media were tried, but no improvement in the isolation success rate was achieved. The effect of host species on ease of isolation was studied. The results obtained suggested it was theFrankia strain and not the host plant species which determined the ease of isolation from Casuarina nodules.     

Production of Metarhizium anisopliae spores using nutrient‐impregnated membranes and its economic analysis

Metarhizium anisopliae spores were produced on nutrient‐impregnated membranes (NIMs). The NIM system involved wetting the membrane with a spore and nutrient suspension, followed by harvesting the spores produced after incubation. The cost efficiency of spore production was assessed for a range of nutrient sources and membrane types. Skim milk powder (20 g l^‐1) was found to be the most cost‐effective nutrient source of the nine nutrients examined. Yield was 5.7 × 10⁶ spores/cm² after 28 days incubation on a paper membrane. Supplementation of the skim milk with either sucrose (2 g l^‐1) or dextrose + KNO₃ maximized yield. Superwipe, an absorbent fibrous material, was the most efficient of 16 membranes tested which ranged from fibreglass mesh to paper and cloth. A series of small pilot plants were built, but the cost efficiency of spore production decreased as the size of the membrane increased from 24 × 24 cm to 270 × 15 cm and up to 100 × 80 cm. Yield on the two smaller pilot plants was over 10⁷spores/cm², but the cost (nutrient and membrane only) of producing 10¹³ spores (standard dose required per hectare) was around $A37 and was found not to be competitive with spore production on grain.     

Observations on the pathogenicity of Pasteuria penetrans, a parasite of root-knot nematodes

A simple test was used to determine whether or not Pasteuria penetrans spores would attach to 17 species of nematodes. All susceptible individuals had spores attached to their cuticles after 24 h of gentle agitation in suspensions containing 10⁵spores/ml. Spores of P. penetrans from six populations of Meloidogyne only adhered to species of Meloidogyne and they adhered in greatest numbers to the species from which they had been originally isolated. Sonication of spores from infected females increased attachment but the effect was dependent on pH and whether the test was conducted in tap or distilled water. Invasion of tomato roots was reduced by up to 86% when, rather than using healthy juveniles, second-stage juveniles bearing 15 or more spores were added to soil at high densities (1000 or 3000/plant); at low densities (500/plant) invasion was not significantly affected. The rate of development of M. incognita juveniles infected with P. penetrans was slower than that of healthy juveniles. The numbers of second-generation of M. incognita were reduced by 82–93% when juveniles encumbered with 1–15 spores were added to soil instead of those bearing no spores. Pasteuria penetrans populations differed in their aggressiveness and when juveniles encumbered with the same number of spores from two populations were added to soil there were differences in the numbers of females that became infected. The implications of these results for the development of P. penetrans as a biological control agent are discussed.     

Spore age and coverslip placement affects germination and post-germination development of Colletotrichum dematium var circinans

Spore suspensions from young (10–14 da; young spores) and old (4 mo; old spores) colonies of PColletotrichum dematium var circinans were placed on slides. Coverslips were left off, placed on in the normal manner, or supported on shims. Slides were placed in moist chambers and incubated in light or dark for up to 48 hrs. Germination and post-germination development were studied. Shimming had some beneficial effect on germination, especially for old spores in dark. In general, more germ-tubes and appressoria were produced on spores under shims than spores with other coverslip treatments. By 48 hrs more old spores under shims germinated, and greater numbers of germ-tubes and appressoria were produced than on other old spores under different coverslip treatments. However, numbers produced were lower than those predicted for comparably treated young spores. Spore age, incubation regime, and placement of coverslips did not affect germ-tube initiation. For all treatments more germ-tubes were initiated from spore tops than bottoms or tips. Fewer germ-tubes were initiated from spore centers than other locations on tops and bottoms, and from both tips than one tip. Approximately 26 % of all appressoria were produced sessile. A higher percentage of sessile appressoria were produced on old spores (80 %) than on young spores (20%).     

Dispersal of Erysiphe graminis and Lycopodium clavatum spores near to the source in a barley crop

In experiments to study dispersal of spores in a crop of barley, a 4-m wide strip of the cultivar Zephyr (a mildew-susceptible variety) was a source of mildew (Eyrsiphe graminis) conidia. Small suction traps, previously calibrated in a wind tunnel, were used to measure spore concentration within and above the crop. Large concentrations of conidia were measured in the crop at the downwind edge of the Zephyr strip but these decreased rapidly with distance downwind. At 1 m concentrations were halved and by 4 m they were no greater than the background concentration measured in the crop upwind of the source. Next to the source, concentrations were much greater within than above the crop and net spore movement (flux) was upwards out of the crop; by 4 m downwind concentrations were greater above the crop and spore flux was reversed. Lycopodium clavatum spores were released in the same crop from a line of point sources. Concentrations also decreased rapidly downwind but, with no background of spores, numbers remained greater within than above the crop further from the source than for E. graminis. Even so by 7 m downwind concentrations in the crop had declined to less than those above. Deposition of L. clavatum spores onto horizontal glass slides in the crop agreed with that expected by settling. However, impaction onto vertical cylinders among plants was much greater than predicted. The reason is not known although turbulent air-flow around plants may, in some way, enhance impaction. Many E. graminis conidia near the source were deposited in clumps. This prevented any accurate prediction of deposition rates as fall speeds of clumps (necessary for prediction) were not known. Not surprisingly, deposition on horizontal slides often exceeded that expected from settling of single spores although it was not always greatest where clumps predominated. The proportion of spores deposited on vertical cylinders and horizontal slides located among plants ranged from 0–02 to 0–27 and from 0–019 to 0–127 of the area dose, respectively. Although these may seem to be small trapping efficiencies, the same deposition rates in a crop with many leaves and stems would rapidly filter most spores from air in the crop and can explain why concentrations were observed to decline so rapidly.     

Spores of the mycorrhizal fungus <Emphasis Type="Italic">Glomus mosseae</Emphasis> host yeasts that solubilize phosphate and accumulate polyphosphates

The present paper reports the presence of bacteria and yeasts tightly associated with spores of an isolate of Glomus mosseae. Healthy spores were surface disinfected by combining chloramine-T 5%, Tween-40, and cephalexin 2.5 g L⁻¹ (CTCf). Macerates of these spores were incubated on agar media, microorganisms were isolated, and two yeasts were characterized (EndoGm1, EndoGm11). Both yeasts were able to solubilize low-soluble P sources (Ca and Fe phosphates) and accumulate polyphosphates (polyPs). Sequence analysis of 18S ribosomal deoxyribonucleic acid showed that the yeasts belong to the genera Rhodotorula or Rhodosporidium (EndoGm1) and Cryptococcus (EndoGm11). Results from inoculation experiments showed an effect of the spore-associated yeasts on the root growth of rice, suggesting potential tripartite interactions with mycorrhizal fungi and plants.     

Gas discharge plasmas are effective in inactivating <Emphasis Type="Italic">Bacillus</Emphasis> and <Emphasis Type="Italic">Clostridium</Emphasis> spores

Bacterial spores are the most resistant form of life and have been a major threat to public health and food safety. Nonthermal atmospheric gas discharge plasma is a novel sterilization method that leaves no chemical residue. In our study, a helium radio-frequency cold plasma jet was used to examine its sporicidal effect on selected strains of Bacillus and Clostridium. The species tested included Bacillus subtilis, Bacillus stearothermophilus, Clostridium sporogenes, Clostridium perfringens, Clostridium difficile, and Clostridium botulinum type A and type E. The plasmas were effective in inactivating selected Bacillus and Clostridia spores with D values (decimal reduction time) ranging from 2 to 8 min. Among all spores tested, C. botulinum type A and C. sporogenes were significantly more resistant to plasma inactivation than other species. Observations by phase contrast microscopy showed that B. subtilis spores were severely damaged by plasmas and the majority of the treated spores were unable to initiate the germination process. There was no detectable fragmentation of the DNA when the spores were treated for up to 20 min. The release of dipicolinic acid was observed almost immediately after the plasma treatment, indicating the spore envelope damage could occur quickly resulting in dipicolinic acid release and the reduction of spore resistance.     

Uninucleate spores of Phycomyces

Summary Under most culture conditions only 0.3% of the vegetative spores of Phycomyces blakesleeanus are uninucleate. On an acidified minimal medium, the uninucleate fraction can be raised up to 4.5% of the spores. The spore population can be fractionated in a gradient under gravity (1xg) yielding fractions that contain over 80% uninucleate spores. These uninucleate spores are fully viable. When the spores to be fractionated are obtained from a heterokaryotic mycelium, the uninucleate fraction produces homokaryotic mycelia.     

Molecular biogeography and origins of the Hawaiian fern flora

Located approximately 4000 km from the nearest continent, the Hawaiian Islands comprise the most isolated archipelago on Earth. This isolation has resulted in a unique flora that includes nearly 200 native ferns and lycophytes, 77% of which are endemic to the islands. Because the Hawaiian Islands are volcanic in origin, all abiotically dispersed organisms must have arrived there via the wind or the water. Fern spores are most likely dispersed through the air, and thus patterns of air movement have undoubtedly played a significant role in determining the geographic origins of the ancestors of the Hawaiian ferns. We have identified four possible climate-based or weather-based spore dispersal hypotheses that could have resulted in the movement of ancestral spores to the Hawaiian Islands: (1) the northern subtropical jetstream, moving spores from Indo-Pacific regions; (2) the trade winds, dispersing spores from Central and North America; (3) storms carrying spores from southern Mexico and/or Central America; and (4) a dispersal mechanism carrying spores from the South Pacific across the equator resulting from the combined influence of a seasonal southern shift of the Intertropical Convergence Zone (ITCZ), Hadley Cell air movement, and the trade winds. Utilizing recently published molecular phylogenetic studies of three fern genera (Dryopteris, Polystichum, andHymenophyllum) and new analyses of three additional genera (Adenophorus, Grammitis, andLellingeria), each of which is represented in the Hawaiian Islands by at least one endemic lineage, we reviewed the biogeographical implications for the Hawaiian taxa in light of the possible common dispersal patterns and pathways. We hypothesize that three of the five endemicDryopteris lineages, both of the endemicPolystichum lineages, at least one endemicHymenophyllum lineage in the Hawaiian Islands, and, perhaps, one endemicGrammitis lineage resulted from ancestral spores of each lineage dispersing to the Hawaiian Islands via the northern subtropical jetstream.Adenophorus is sister to a mostly neotropical clade, therefore, it is likely that the ancestor of the Hawaiian clade dispersed to the Hawaiian Islands via the trade winds or a storm system. The ancestor of the endemicLellingeria lineage may have dispersed to the Hawaiian Islands from the neotropics via the trade winds or a storm system, or from the South Pacific across the equator through the combination of a seasonal southern shift of the ITCZ, Hadley Cells, and the trade winds.     

ULTRASTRUCTURAL STUDIES OF IN SITU DEVONIAN SPORES: BARINOPHYTON CITRULLIFORME

Each sporangium in the Upper Devonian taxon Barinophyton citrulliforme contains both microspores and megaspores. Microspores range up to 50 μm in diam and possess a homogeneous sporoderm characterized by an outer separable layer. The sporoderm of the megaspores (up to 900 μm) is constructed of sporopollenin units that are loosely arranged in the outer portion of the wall, and that give the megaspore wall a spongy organization. Ultrastructural evidence suggests that the small spores were not abortive megaspores, but that both spore types were functional. The spores of this plant, as well as other Devonian spores that show less dramatic size differences, are suggested as demonstrating a phase in the evolution of heterospory where sex determination was established in spores within the same sporangium prior to the evolution of micro- and megasporangia.     

FREE AMINO ACID CHANGES DURING GERMINATION OF TELIOSPORES OF THE WHEAT BUNT FUNGUS,TILLETIA CARIES

Teliospores were aerated and agitated in a mineral salts medium and their free amino acid contents were analyzed at eight different times, from shortly after imbibition of water until just before germ tube emergence. In addition to the common amino acids, eight unidentified ninhydrin-positive components were detected. About 50 % or more of nearly each of the amino acids diffused out of the spores during the initial phase of germination. These released amino acids were actively taken up by the spores during the latter stages of germination. The free amino acids in largest amounts in the dormant spores of T. caries were arginine 15.0, glutamic acid 6.3, and alanine 3.7 μmoles per g dry spores. Together these three amino acids accounted for about 71 % of the total free amino acids in dormant spores of T. caries and T. controversa. The total amounts of free amino acids in spores of common bunt were much higher than in spores of dwarf bunt.     

Secondary leaf fall of Hevea brasiliensis: factors affecting the production, germination and viability of spores of Colletotrichum gloeosporioides

The optimum temperature for growth and sporulation of Colletotrichum gloeosporioides from Hevea brasiliensis was between 26 and 32 ^oC, whereas spore germination exceeded 90% between 21.5 and 30.5 ^oC. Germination decreased in culture after 3 days, and on exposure of spores to sunlight or oven heat (46 ^oC) for 10 min. Spore viability and germination were sensitive to atmospheric humidity; at 99% r.h. germination was half that at 100% r.h. and was negligible below 97% r.h. Germination decreased by up to 30% after 3 h storage at 80% r.h. Continuous light favoured spore production in vitro, but spores produced in the dark had a higher percentage germination. No differences were detected between the numbers of spores germinating on leaves of different ages, although there were slightly more on susceptible cultivars and in the presence of extracts of uninfected susceptible leaves. Extracts from, infected leaves depressed spore germination, as did concentrations above 5 times 10⁵ spores/ml. The highest % germination was observed when naturally infected leaves were dry-stored for up to 20 days and then incubated for 2 days in a moist chamber.