Vesicular-arbuscular mycorrhizal fungi in coastal dune plant communities I. Spore formation ofGlomus spp. predominates under a patch ofElymus mollis

Vesicular-arbuscular (VA) mycorrhizal fungi in pure patches of coastal dune plantsElymus mollis, Wedelia prostrata andZoysia macrostachya were examined for frequency of occurrence and number of spores of VA mycorrhizal fungi over one year. Six species in three genera of VA mycorrhizal fungi were recovered. Under a patch ofE. mollis, spores ofAcaulospora sp. 1,Glomus tortuosum, Glomus sp. 1,Glomus sp. 2 andScutellospora gregaria were recovered. Spores ofGlomus spp. were most common. In patches ofW. prostrata andZ. macrostachya spores ofAcaulospora sp. 1,G. tortuosum, Glomus sp. 1,Glomus sp. 2,S. gregaria andScutellospora sp. 1 were found.Contribution No. 112, Laboratories of Plant Pathology and Mycology, Institute of Agriculture and Forestry, University of Tsukuba.     

Abundance of arbuscular mycorrhizal fungi spores in different environments in a tropical rain forest, Veracruz, Mexico

 The aim of this study was to compare mycorrhizal abundance and diversity in sites with different regimes of disturbance in a tropical rain forest at Los Tuxtlas, Veracruz, Mexico. Arbuscular mycorrhizal spores were quantified at two sites: closed canopy and gaps in the forest. Data were recorded during dry, rainy, and windy ("nortes") seasons. Spores of eight Glomus species, sporocarps of three Sclerocystis species, three species of Acaulospora and two of Gigaspora were found. Significant differences in the number of species and spores were found among seasons. The highest numbers of species and spores were observed during the dry season, with a marked decrease during the rainy season. Our results show that disturbance does not but seasonality does affect abundance and richness of mycorrhizal spores in this tropical wet forest. Accepted: 11 October 1998     

Conservation genetics of the threatened horned grebe (<Emphasis Type="Italic">Podiceps auritus</Emphasis> L.) population of the Magdalen Islands,Québec

The horned grebe (Podiceps auritus) population of the Magdalen Islands in the St. Lawrence Gulf (Québec, Canada) has declined sharply over the last decades. It is the only breeding population of this species in eastern North America with nearest breeding populations being >2500 km apart in western North America and Europe, We used three types of genetic markers: mitochondrial (mt) DNA ND2 sequence, α-enolase intron sequence, and 25 amplified fragment length polymorphism loci (AFLPs) to quantify the genetic diversity within the Magdalen Island population and to assess its genetic distinctiveness relative to populations from western Canada (five sites) and Iceland (one site). The Magdalen Island population retained a comparable amount of genetic diversity to the average diversity observed across all populations in all three markers. Horned grebe mtDNA sequences formed a monophyletic group and nearly all haplotypes present in Québec were found elsewhere. In the ND2 fragment, populations partitioned into two groups corresponding to subspecies (Iceland versus North American sites) and more strongly in three groups according to geographic disjunctions (Iceland versus Québec versus western Canada). In contrast, there was no evidence of structure between sites in the α-enolase intron. In the AFLPs, Iceland showed the greatest level of differentiation, followed by the Québec and British Columbia populations. For conservation purposes, we suggest that the Magdalen Islands population should be recognized as a separate unit.     

Tree-ring analysis of white cedar (Thuja occidentalis L.) archaeological and historical wood in Québec City (Québec,Canada)

In Québec City, a segment of an old wooden palisade built for protection was found buried in situ. The palisade was excavated by the Laval University archaeology field school in 2004–2005, and 29 posts were recovered and sampled. The palisade enclosed the Intendant's Palace compound, which was the residence of the governor of New France at the end of the 17th century. Tree-ring analysis was performed on wood excavated from the Intendant's Palace archaeological site (PDI) and additional wood from two historical military buildings, the Artillery Park (ART) (early 18th century) and the Québec Citadel (CIT) (17th–19th centuries). Wood identification revealed that white cedar (Thuja occidentalis L.) was used for wood construction at the three sites. Many trees used for the construction of the PDI palisade were felled after the 1690 growing season, likely in September/October 1690. Posts probably came from trees growing close to the site on the banks of the Saint-Charles River. A white cedar ring-width chronology from the Rimouski area, approximately 300 km northeast of Québec City, along the St. Lawrence River, was used for cross-dating. Archaeological and historical wood samples from two of the three sites (PDI and ART) were first assembled in a 235-year tree-ring chronology, called the Québec chronology, extending from 1489 to 1723. The two master chronologies (Québec and Rimouski) were merged into a single 513-year tree-ring chronology (1489–2001), called the Saint-Laurent chronology.     

Detection of high-phosphorus tolerant VAM-fungi colonizing hops and peppermint

Summary In a continuing search for field sources of endomycorrhizal fungi that tolerate high levels of available phosphorus in soil, samples were obtained from long-established liberally fertilized hops (Humulus lupulus L.) and peppermint (Mentha piperita L.) fields. In hops fields, where extractable P (Bray) levels ranged from 21–196 ppm, spores of twoAcaulospora spp. and sixGlomus spp. were isolated. From peppermint fields with P levels of 44 to 244 ppm, spores of oneAcaulospora sp., fourGlomus spp. and oneGigaspora sp. were obtained. Vesicular-arbuscular mycorrhizal (VAM) fungi were found colonizing most roots to some extent, despite the very high fertility of several sites. Although percentages of colonization in hops tended to be low, ranging from 0 to 9.3%, colonizations in peppermint roots were considerably higher averaging 26.5% between the sampled fields, notwithstanding P levels as high as 244 ppm. Curiously, considerable external VAM hyphae were found adherent to or entangling roots in many cases, even where percentage of root length with internal VAM structures was low. The functional benefit, neutrality, or detriment to plants of such high-P tolerant species remains to be determined.Contribution from the USDA-ARS, Horticultural Crops Research Laboratory and the Dept. of Soil Science, Oregon State University, in cooperation with the Oregon State University Agricultural Experiment Station, Corvallis, OR 97331. Technical paper no. 6979 of the latter     

Growth and nitrogen fixation ofAzolla pinnata andAzolla caroliniana as affected by urea fertilizer and their influence on rice yield

Soils from avocado (Persea americana Mill.) orchards in Israel (IS) and California (CA), both sites with a Mediterranean climate, were sampled and analyzed for the species and quantities of vesicular-arbuscular mycorrhizal fungus (VAMF) spores in them, and for soil physical and chemical characteristics.Numbers of spores were similar in soil from IS and CA but the dominant VAMF species were very different. In IS the most common fungi were Sclerocystis sinuosa and Glomus macrocarpum. In CA, Gl. constrictum was present in every orchard examined and Gl. fasciculatum was nearly as widespread. Acaulospora spp. and other Glomus spp. also were found, including A. elegans which has never before been reported from CA.The differences in VAMF populations and species constituents found on two continents but in areas with similar climates and soil types may be due to host or edaphic factors. Different avocado rootstocks are used in the two countries and lower pH and higher soil fertility levels were present in CA soils.The total VAMF spore populations in each orchard was about 275 per 100 mL soil. The population level was not correlated with any of the soil physical or chemical characteristics examined nor with avocado cultivar or age. In IS no fungus spores were found in three orchards; available P, Ca, Mg and Cu levels were high in these soils.     

Diversity and efficiency of arbuscular mycorrhizal fungi in soils from organic chili (Capsicum frutescens) farms

No previous studies have been conducted on the diversity and population of arbuscular mycorrhizal fungi (AMF) in relation to organically grown chili (Capsicum frutescens L.) in Thailand. This study was carried out to investigate the diversity and status of AMF populations at four organically managed farms in Ubon Ratchathani and Sisaket provinces. The effects of each AMF species on the growth and nutrient uptake of chili grown in sterile, organically managed soil were determined. Fourteen AM fungal taxa belonging to the genera Acaulospora (4 spp.), Entrophospora (1 sp.), Glomus (7 spp.) and Scutellospora (2 spp.) were found. Among these, Glomus was the dominant genus found at all sites, followed by Acaulospora. The spore density and root colonization of AMF on chili did not vary significantly among the sites. The effects of ten selected AMF species on the growth of chili showed that Gl. clarum RA0305 increased the growth, flowering, and fruit production of chili, and also increased the P uptake significantly, compared to non-mycorrhizal plants. This fungus showed the highest potential as a promoter of growth, flowering and yield in organically managed chili production.     

Interactions between water-stress and different mycorrhizal inocula on plant growth and mycorrhizal development in maize and sorghum

Maize (Zea mays) and sorghum (Sorghum bicolor) were inoculated with a range of VAM fungi and grown under water-stressed and unstressed conditions. There was considerable variation amongst the inocula in their effects on plant growth. Inoculation with Glomus clarum produced the biggest plants in each host, with Glomus monosporum and Acaulospora sp. giving the least growth overall. Root infection produced by the different inocula also varied, but levels were not correlated with effects on plant growth. Water-stress reduced plant growth, with the effects not being altered by mycorrhizal infection. VAM infection levels were not affected by water-stress. Spore production from most inocula was reduced by water-stress, both in total spore numbers and in terms of spores per gram plant weight. Sporulation of G. clarum, G. epigeum and G. monosporum were affected less by stress than were the other inocula. Spore production was in general greater on sorghum than on maize, but the host effect varied amongst the inocula.     

Genetic structure of the white‐footed mouse in the context of the emergence of Lyme disease in southern Québec

The white‐footed mouse (Peromyscus leucopus) has expanded its northern limit into southern Québec over the last few decades. P. leucopus is a great disperser and colonizer and is of particular interest because it is considered a primary reservoir for the spirochete bacterium that causes Lyme disease. There is no current information on the gene flow between mouse populations on the mountains and forest fragments found scattered throughout the Montérégie region in southern Québec, and whether various landscape barriers have an effect on their dispersal. We conducted a population genetics analysis on eleven P. leucopus populations using eleven microsatellite markers and showed that isolation by distance was weak, yet barriers were effective. The agricultural matrix had the least effect on gene flow, whereas highways and main rivers were effective barriers. The abundance of ticks collected from mice varied within the study area. Both ticks and mice were screened for the presence of the spirochete bacterium Borrelia burgdorferi, and we predicted areas of greater risk for Lyme disease. Merging our results with ongoing Lyme disease surveillance programs will help determine the future threat of this disease in Québec, and will contribute toward disease prevention and management strategies throughout fragmented landscapes in southern Canada.     

Indigenous Arbuscular Mycorrhizal Fungi Associated with Acacia albida Del. in Different Areas of Senegal

The influences of seasons, plant age, and physicochemical properties of the soil on surface and deep biological arbuscular mycorrhizal fungus parameters associated with Acacia albida were assessed in different areas of Senegal. More indigenous arbuscular mycorrhizal propagules were found in the localities of the Sudano-Guinean zone (Djinaki and Kabrousse) than in those of the Sahelian zone (Louga and Diokoul), and species belonging to the genera Glomus, Gigaspora, Acaulospora, and Sclerocystis prevailed. The numbers of total and viable spores increased more during the rainy season than during the dry season (about 108% more total spores and 262% more viable spores). Similarly, both total and viable spores were more prevalent around young Acacia trees than old trees. However, the intensities of root colonization did not differ in each ecoclimatic zone.     

Seasonal variation of arbuscular mycorrhizal fungi in temperate grasslands along a wide hydrologic gradient

We studied seasonal variation in population attributes of arbuscular mycorrhizal (AM) fungi over 2 years in four sites of temperate grasslands of the Argentinean Flooding Pampas. The sites represent a wide range of soil conditions, hydrologic gradients, and floristic composition. Lotus glaber, a perennial herbaceous legume naturalised in the Flooding Pampas, was dominant at the four plant community sites. Its roots were highly colonised by AM fungi. Temporal variations in spore density, spore type, AM root colonisation, floristic composition and soil chemical characteristics occurred in each site and were different among sites. The duration of flooding had no effect on spore density but depressed AM root colonisation. Eleven different types of spores were recognized and four were identified. Two species dominated at the four sites: Glomus fasciculatum and Glomus intraradices. Spore density was highest in summer (dry season) and lowest in winter (wet season) with intermediate values in autumn and spring. Colonisation of L. glaber roots was highest in summer or spring and lowest in winter or autumn. The relative density of G. fasciculatum and G. intraradices versus Glomus sp. and Acaulospora sp. had distinctive seasonal peaks. These seasonal peaks occurred at all four sites, suggesting differences among AM fungus species with respect to the seasonality of sporulation. Spore density and AM root colonisation when measured at any one time were poorly related to each other. However, spore density was significantly correlated with root colonisation 3 months before, suggesting that high colonisation in one season precedes high sporulation in the next season.     

How did common ragweed (Ambrosia artemisiifolia L.) spread in Québec? A historical analysis using herbarium records

Aim To reconstruct the spread of common ragweed (Ambrosia artemisiifolia L.; Asteraceae) using herbarium specimens to document whether the habitat preferences of this plant have shifted through time. Location Southern Québec. Methods Herbarium specimens stored in the main herbaria of southern Québec were used to reconstruct the spread of common ragweed. All data (sampling location, year of sampling, habitat characteristics, etc.) were incorporated into a geographical information system. Maps indicating the spatial distribution of common ragweed were produced for four time periods. The cumulative number of locations was plotted against time to construct invasion curves. The sequence of habitats where herbarium specimens were collected was also reconstructed. Results A data base incorporating 707 common ragweed herbarium specimens was constructed for this study. The spread of common ragweed in most regions of southern Québec was initiated at the beginning of the 20th century. Herbarium specimens suggest that common ragweed first spread along river corridors. Specimens of common ragweed were not collected in agricultural fields before the mid‐1920s, nor along roads and railways before the mid‐1930s. The colonization of a large number of agricultural fields by common ragweed probably began with seed‐contaminated crops, but was certainly accelerated by the dispersal of seeds from populations growing along nearby roads. Main conclusions Herbarium specimens suggest that common ragweed has been present in southern Québec for at least 200 years, but the species was probably restricted to the Montréal area during the 19th century. It is likely that the development of the road network in Québec since the mid‐1930s significantly contributed to the spread of common ragweed. Controlling common ragweed solely in agricultural fields would not prevent the re‐infestation of crops, because roadsides would act as refuges for the weed.     

Possible role of disturbance in shaping the northern distribution of Pinus resinosa

Abstract. The objective of this study is to determine the factors responsible for the distribution of Pinus resinosa (red pine) at its northern limit in northwestern Québec. Pinus resinosa is found only on islands and protected lake shores at its northern distribution boundary. The influence of climate on the germination of P. resinosa seed and on the phenology of P. resinosa was investigated in the Lake Duparquet region of northwestern Québec. The results indicate that P. resinosa seed readily germinates at island- and inland sites, which indicates that germination is not responsible for the distribution of P. resinosa in the Lake Duparquet region. Also, cones and seeds developed normally at island sites and an inland plantation, which suggests that seed production is not hindering the expansion of P. resinosa. These results, together with other studies in the literature, suggest that no climatic factor could explain the present distribution of P. resinosa nor its northern limit. The fire regime appears to be responsible for the restriction of P. resinosa to lake environments and hinders the northward expansion of P. resinosa. The typical crown fire regime of the boreal forest is not conducive for P. resinosa regeneration and restricts the species to fire-sheltered locations such as islands and protected lake shores.     

Canid hybridization: contemporary evolution in human‐modified landscapes

Contemporary evolution through human‐induced hybridization occurs throughout the taxonomic range. Formerly allopatric species appear especially susceptible to hybridization. Consequently, hybridization is expected to be more common in regions with recent sympatry owing to human activity than in areas of historical range overlap. Coyotes ( Canis latrans) and gray wolves ( C. lupus) are historically sympatric in western North America. Following European settlement gray wolf range contracted, whereas coyote range expanded to include eastern North America. Furthermore, wolves with New World (NW) mitochondrial DNA (mtDNA) haplotypes now extend from Manitoba to Québec in Canada and hybridize with gray wolves and coyotes. Using mtDNA and 12 microsatellite markers, we evaluated levels of wolf‐coyote hybridization in regions where coyotes were present (the Canadian Prairies, n = 109 samples) and absent historically (Québec, n = 154). Wolves with NW mtDNA extended from central Saskatchewan (51°N, 69°W) to northeastern Québec (54°N, 108°W). On the Prairies, 6.3% of coyotes and 9.2% of wolves had genetic profiles suggesting wolf‐coyote hybridization. In contrast, 12.6% of coyotes and 37.4% of wolves in Québec had profiles indicating hybrid origin. Wolves with NW and Old World ( C. lupus) mtDNA appear to form integrated populations in both regions. Our results suggest that hybridization is more frequent in historically allopatric populations. Range shifts, now expected across taxa following climate change and other human influence on the environment, might therefore promote contemporary evolution by hybridization.     

Selection of efficient vesicular-arbuscular mycorrhizal fungi for wetland rice — a preliminary screen

Eighteen different VA mycorrhizal fungi were screened for their symbiotic responses with wet land rice cultivar Prakash (IET 2254) under pot culture. Of the 18 fungi, Acaulospora sp. (ICRISAT), Glomus fasciculatum (Riverside) and G. mosseae (Invermay) were found to be the best in improving plant height, tiller number, total biomass, panicle number, grain weight and plant P and Zn concentrations. Increases in grain yield caused by inoculation with Acaulospora sp. (ICRISAT), G. fasciculatum (Riverside) and G. mosseae (Invermay) were 62%, 59% and 35%, respectively.     

Some Mediterranean plant species (Lavandula spp. and Thymus satureioides) act as potential ‘plant nurses’ for the early growth of Cupressus atlantica

The mycorrhizal status of several representative shrub species (Lavandula spp. and Thymus satureioides) in Moroccan semiarid ecosystems, was evaluated as well as their contribution to the mycorrhizal potential of the soil. Furthermore, the rhizosphere soils collected under these target species were tested for their influence on the growth of Cupressus atlantica, a tree species whose natural stands has declined in this area. Soil samples were collected from the rhizosphere of L. stoechas, L. dentata and of C. atlantica existing in the experimental area. Control samples were randomly collected from bare soil sites, away from plant influence.All the target species formed AM symbiosis and the extent of AM fungal colonization was not significantly different between plant species. No significant difference was detected between the total number of AM fungal spores of the bare soil and those recorded in the root zones of target species and C. atlantica. Three genera of AM fungi (Scutellospora, Glomus and Acaulospora) were present in the rhizospheres of the plant species and in the bare soil.The number of mycorrhizal propagules in soil originating from around the four target plant species was significantly higher than the one in the bare soil (Figure 1). The most probable number (MPN) of mycorrhizal propagules per 100 g of dry soil ranged from 7.82 (bare soil) to 179.7 (L. dentata and C. atlantica) and 244.5 (L. stoechas and T. satureioides). As the total number of spores was not different for the soil of different origins, the increase of the mycorrhizal soil infectivity (MSI) mainly resulted from larger AM mycelial networks that constituted the main source of AM fungal inoculum. In addition, this MSI enhancement was linked with changes in the functioning of soil microbial communities. In a glasshouse experiment, the growth of C. atlantica seedlings was significantly higher in the C. atlantica and in the shrub species soils than in the bare soil. Although the AM inoculum potential is not sufficient to ensure the development of forest trees in Mediterranean ecosystems, the use of plant nurses such as T. satureioides or Lavandula spp. could be of great interest to restore a self-sustaining vegetation cover to act against desertification.     

Distribution, abundance, and seasonal ecology of Listronotus maculicollis (Coleoptera: Curculionidae) on golf courses in Québec, Canada

The weevil Listronotus maculicollis Dietz (Coleoptera: Curculionidae) is a major pest of annual bluegrass, Poa annua L., on golf courses in northeastern North America. To determine the distribution, abundance, and seasonal ecology of L. maculicollis on golf courses in Québec, Canada, we sampled 19 golf courses (GC1-GC19) from different geographic and climatic conditions during 2001, 2002, and 2003. L. maculicollis was found on all golf courses except GC19, which was located in northeastern Québec. In most sites, L. maculicollis completed two generations per year. A linear regression model comparing L. maculicollis larval densities as a function of spatial coordinates revealed that L. maculicollis were more abundant in western Québec than in eastern Québec. Pearson correlations on the probability of both L. maculicollis larval and pupal presence with soil parameters indicated significant positive correlations for fine sand (larvae) and soil pH (pupae) and negative correlations for gravel.     

Factors influencing aboveground production of Scirpus marshes in the St. Lawrence estuary,Québec,Canada

Aboveground production of macrophytes in tidal marshes was studied for 3 years at Montmagny and Cap St. Ignace on the south shore of the St. Lawrence River in Québec, Canada. Year-to-year variation of production of the dominant species, Scirpus americanus Pers., was observed and related to variation in weather during the growing season. With the exception of Zizania aquatica L., relative production of the macrophytes for different parts of the marshes remained constant in successive years. A multiple regression procedure was used to establish the relationship between production and a series of independent variables including biotic (goose use and plant competition) and abiotic factors (submersion, substrate hardness, soil texture and sedimentation). A lower percentage of organic matter in the soil and a firm substrate were associated with a greater production of S. americanus. Accretion of sediments was positively correlated with the production of S. americanus and Sagittaria spp., whereas the percentage of time of submersion was negatively related with production of Sagittaria spp., Eleocharis spp. and Scirpus torreyi Olney. Competitive interference was apparent between S. americanus and S. torreyi and between Eleocharis spp. and Zizania spp. No measured abiotic characteristic of the marsh explained the variation of Zizania production.     

Arbuscular mycorrhizal fungi associated with Artemisia umbelliformis Lam, an endangered aromatic species in Southern French Alps, influence plant P and essential oil contents

Root colonization by arbuscular mycorrhizal (AM) fungi of Artemisia umbelliformis, investigated in natural and cultivated sites in the Southern Alps of France, showed typical structures (arbuscules, vesicles, hyphae) as well as spores and mycelia in its rhizosphere. Several native AM fungi belonging to different Glomeromycota genera were identified as colonizers of A. umbelliformis roots, including Glomus tenue, Glomus intraradices, G. claroideum/etunicatum and a new Acaulospora species. The use of the highly mycorrhizal species Trifolium pratense as a companion plant impacted positively on mycorrhizal colonization of A. umbelliformis under greenhouse conditions. The symbiotic performance of an alpine microbial community including native AM fungi used as inoculum on A. umbelliformis was evaluated in greenhouse conditions by comparison with mycorrhizal responses of two other alpine Artemisia species, Artemisia glacialis and Artemisia genipi Weber. Contrary to A. genipi Weber, both A. umbelliformis and A. glacialis showed a significant increase of P concentration in shoots. Volatile components were analyzed by GC–MS in shoots of A. umbelliformis 6 months after inoculation. The alpine microbial inoculum increased significantly the percentage of E-β-ocimene and reduced those of E-2-decenal and (E,E)-2-4-decadienal indicating an influence of alpine microbial inoculum on essential oil production. This work provides practical indications for the use of native AM fungi for A. umbelliformis field culture.