Studies on soil fungi III. Seasonal variation and distribution of microfungi in some soils of Andhra Pradesh (India)

The seasonal variation and distribution of microfungi in four soil types collected from two districts of Andhra Pradesh (India) were studied.Besides soil type and surface vegetation, it appears from the present study that soil moisture, organic matter, potassium, calcium, iron and phosphorus contents also may affect the fungal numbers favourably, while chlorides, total soluble salts, total nitrogen and manganese contents may have an adverse effect.Even alkaline soils harbour greater numbers of fungi, but small fluctuations in the pH seem to influence the fungal numbers in soils inversely.A total of 101 species representing 43 genera were isolated. These included 18 Phycomycetes, 5 Ascomycetes, 72 Fungi Imperfecti, 5 Mycelia Sterilia and a single Myxomycete. The order of occurrence of the chief genera of fungi isolated wasAspergillus, Penicillium, Fusarium, Pythium, Curvularia, Phoma, Cunninghamella, Rhizopus, Alternaria andTrichoderma.A large number of genera and species were found common to the forest, maize field, garden and uncultivated soils; and the fungal flora was also not very much different from those recorded from various parts of the world.     

Factors related to diversity of decomposer fungi in tropical forests

Recent studies suggest that host-preferences are common among certain groups of tropical fungal decomposers but rare in others, and sometimes occur where we least expect them. Host preferences among microfungi and ascomycetes that decompose leaf litter are common but usually involve differences in relative frequencies more than presence/absence, so their diversity may be loosely correlated with species richness of host trees. Strong host-specificity appears to be rare among wood decomposer fungi, whereas characteristics of their substrata and habitat are very important for this group. Anthropogenic disturbance predisposed a tropical forest to subsequent hurricane damage, and the resulting direct and indirect effects on host diversity and habitat heterogeneity were reflected in the decomposer fungal community more than sixty years after the original disturbance. While species richness of dictyostelid slime molds and functional diversity of their bacterial prey increased with disturbance, the more diverse microfungi and ascomycetes were apparently negatively affected by disturbance.     

Endophytic fungi from Peruvian highland and lowland habitats form distinctive and host plant-specific assemblages

Biodiversity and biogeography of leaf-inhabiting endophytic fungi have not been resolved yet. This is because host specificity, life cycles and species concepts, in this heterogeneous ecological guild of plant-associated microfungi, are far from being understood. Even though it is known that culture-based collection techniques are often biased, this has been the method of choice for studying fungal endophytes. Isolation of fungal endophytes only through culture-based methods could potentially mask slow growing species as well as species with low prevalence, preventing the capture of the communities’ real diversity and composition. This bias can be partially resolved by the use of cultivation-independent approaches such as direct sequencing of plant tissue by next generation techniques. Irrespective of the chosen sampling method, an efficient analysis of community ecology is urgently needed in order to evaluate the driving forces acting on fungal endophytic communities. In the present study, endophytic ascomyceteous fungi from three different plant genera (Vasconcellea microcarpa, Tillandsia spp., and Hevea brasiliensis) distributed in Peru, were isolated through culture-based sampling techniques and sequenced for their ITS rDNA region. These data sets were used to assess host preferences and biogeographic patterns of endophytic assemblages. This study showed that the effect of the host’s genetic background (identity) has a significant effect on the composition of the fungal endophytic community. In other words, the composition of the fungal endophytic community was significantly related to their host’s taxonomic identity. However, this was not true for all endophytic groups, since we found some endophytic groups (e.g. Xylariales and Pleosporales) occurring in more than one host genus. Findings from this study promote the formulation of hypotheses related to the effect of altitudinal changes on the endophytic communities along the Eastern Andean slopes. These hypotheses and perspectives for fungal biodiversity research and conservation in Peru are addressed and discussed.     

Phylogenetic congruence between subtropical trees and their associated fungi

Recent studies have detected phylogenetic signals in pathogen–host networks for both soil‐borne and leaf‐infecting fungi, suggesting that pathogenic fungi may track or coevolve with their preferred hosts. However, a phylogenetically concordant relationship between multiple hosts and multiple fungi in has rarely been investigated. Using next‐generation high‐throughput DNA sequencing techniques, we analyzed fungal taxa associated with diseased leaves, rotten seeds, and infected seedlings of subtropical trees. We compared the topologies of the phylogenetic trees of the soil and foliar fungi based on the internal transcribed spacer (ITS) region with the phylogeny of host tree species based on matK, rbcL, atpB, and 5.8S genes. We identified 37 foliar and 103 soil pathogenic fungi belonging to the Ascomycota and Basidiomycota phyla and detected significantly nonrandom host–fungus combinations, which clustered on both the fungus phylogeny and the host phylogeny. The explicit evidence of congruent phylogenies between tree hosts and their potential fungal pathogens suggests either diffuse coevolution among the plant–fungal interaction networks or that the distribution of fungal species tracked spatially associated hosts with phylogenetically conserved traits and habitat preferences. Phylogenetic conservatism in plant–fungal interactions within a local community promotes host and parasite specificity, which is integral to the important role of fungi in promoting species coexistence and maintaining biodiversity of forest communities.     

Complex host-pathogen coevolution in the Apterostigma fungus-growing ant-microbe symbiosis

Background  

The fungus-growing ant-microbe symbiosis consists of coevolving microbial mutualists and pathogens. The diverse fungal lineages that these ants cultivate are attacked by parasitic microfungi of the genus Escovopsis. Previous molecular analyses have demonstrated strong phylogenetic congruence between the ants, the ants-cultivated fungi and the garden pathogen Escovopsis at ancient phylogenetic levels, suggesting coevolution of these symbionts. However, few studies have explored cophylogenetic patterns between these symbionts at the recent phylogenetic levels necessary to address whether these parasites are occasionally switching to novel hosts or whether they are diversifying with their hosts as a consequence of long-term host fidelity.     

Biotic and abiotic constraints that facilitate host exclusivity of Gondwanamyces and Ophiostoma on Protea

Estimations of global fungal diversity are hampered by a limited understanding of the forces that dictate host exclusivity in saprobic microfungi. To consider this problem for Gondwanamyces and Ophiostoma found in the flower heads of Protea in South Africa, we determined the role of various factors thought to influence their host exclusivity. Results showed that various biotic and abiotic factors influence the growth and survival of these fungi in vitro. Monitoring temperature and relative humidity (RH) fluctuations within infructescences in vivo revealed considerable microclimatic differences between different Protea spp. Fungal growth and survival at different RH levels experienced in the field suggested that this factor does not play a major role in host exclusivity of these fungi. Maximum temperatures within infructescences and host preferences of the vectors of Gondwanamyces and Ophiostoma appear to play a substantial part in determining colonisation of Protea in general. However, these factors did not explain host exclusivity of specific fungal species towards particular Protea hosts. In contrast, differential growth of fungal species on media containing macerated tissue of Protea showed that Gondwanamyces and Ophiostoma grow best on tissue from their natural hosts. Thus, host chemistry plays a role in host exclusivity of these fungi, although some species grew vigorously on tissue of Protea spp. with which they are not naturally associated. A combination of host chemistry and temperature partially explains host exclusivity, but the relationship for these factors on the tested saprobic microfungi and their hosts is clearly complex and most likely includes combinations of various biotic and abiotic factors including those emerging from this study.     

Open relationships in the castles of clay: high diversity and low host specificity of Termitomyces fungi associated with fungus-growing termites in Africa

In the African and Asian tropics, termites of the subfamily Macrotermitinae play a major role in the decomposition of dead plant material. Their ecological success lies in the obligate mutualism of the termites with fungi of the genus Termitomyces. Before the advent of molecular studies, the interaction with these fungi was poorly understood. Here, we combined available ITS sequence data from West, Central, and South Africa with data of 39 new samples from East Africa to achieve the most comprehensive view of the diversity and host specificity of Termitomyces symbionts across Africa to date. A high amount of sequence divergence in the ITS sequences was found; 11 different Termitomyces lineages in East Africa and >30 lineages across Africa were identified, and the expected diversity is estimated to be about 41 lineages. The fungal lineages belong to four major clades, each almost exclusively associated with one termite host genus. Analysis of molecular variance revealed that 40% of the ITS sequence variation occurred between host genera, indicating close co-evolution at this level. However, within host genera, fungal lineages and haplotypes were frequently shared among host species and sampling localities, except for fungal symbionts of Odontotermes. Horizontal transmission of fungal symbionts may facilitate the transfer of haplotypes and species among hosts. However, at present, we have little understanding of the maintenance of specificity at the genus level. Possible explanations range from substrate specificity of fungi to an active selection of fungi by termites.     

Pioneer forays for fungi in the Darién Province in Eastern Panama: quintuplicating the knowledge on fungi in this area by five days of fieldwork

For the Darién Province, an area larger than Jamaica in Eastern Panama, up to now only 19 species of fungi, mainly lichens and plant parasitic microfungi, have been known. Two general mycological forays including most major groups of fungi were carried out in this area for the first time. During 3 days mostly in secondary vegetation and 2 days in pristine forest, about 104 specimens of macro- and microfungi were collected, of which 85 were identified as 76 species of which all but one were new records for the Darién Province. As a result, knowledge on fungal taxa in that region has risen from 19 to 94, i.e. by a factor of five. Although common and easily-spotted species were preferred during collection, 16 (more than 20%) of the species identified were new for Panama, notably two species of Agaricales, Hygroaster nodulisporus and Leucopaxillus gracillimus, and four microfungi on plants, Cercosporella leucaenae, Coccomyces delta, Meliola bixae, and Stigmina anacardii. The records of the species are presented together with specimen data, references, and photos of selected species. As shown by this study, fungi in tropical Panama are highly diverse, mostly unknown, and further mycological field work is urgently needed because habitats are destroyed and fungi specific to them are lost forever.     

Host- and tissue-specificity of moss-associated Galerina and Mycena determined from amplicon pyrosequencing data

The genetic diversity of two agaricoid saprotroph genera, Galerina and Mycena, and their distribution across bryophyte host species, and within bryophytes' photosynthetic and senescent tissues, was assessed using data from two pyrosequencing biodiversity inventories of bryophilous fungi. A total of 9 498 Galerina and 5 731 Mycena reads were mapped to branches broadly distributed throughout backbone trees, reflecting no obvious evolutionary specialization of particular fungal lineages to moss hosts/substrata. Although a few OTUs occurred with equal frequency across the hosts, most exhibited some degree of specialization to one or more bryophytes, indicating that the quality of different mosses as substratum varies between species. With one exception, all Galerina and Mycena OTUs were more frequent and abundant in senescent than photosynthetic tissues, likely reflecting saprotrophic nutritional modes in the fungi. A single Mycena OTU showed considerable colonization of both tissues, which may reflect an opportunistic parasitic or endophytic lifestyle.     

The biogeographical distribution of microfungi associated with three palm species from tropical and temperate habitats

The microfungi of three palm species were investigated in their natural habitats and in habitats where the palms were cultivated outside their natural ranges. The palms that were selected differed in their habitats and ecology. Archontophoenix alexandrae is endemic to tropical rainforests in Australia, Cocos nucifera is pan‐tropical and Trachycarpus fortunei occurs in warm‐temperate China. Different assemblages of fungi were found in association with palms in temperate regions as compared to those in tropical regions. These differences were more related to climatic influences than to the hosts sampled, as few fungi were host‐species specific. The status of the hosts at the site, i.e. indigenous or introduced, and the degree of disturbance of the habitats within which the palms grew were also influential. When sampled in its natural habitat, Archontophoenix alexandrae had a distinct palmicolous mycota typical of other palms in tropical rainforests. Outside of the palm’s natural habitat, a widely different mycota were recorded that comprised tropical species of a more plurivorous nature. A similar plurivorous assemblage characterized the fungi associated with Cocos nucifera, probably due to the palm’s long history of cultivation. Similarly, plurivorous, but temperate or widespread fungi were associated with Trachycarpus fortunei, both within and outside of its natural habitat. This palm is also highly cultivated. A reduction in palm fungi associated with palms in disturbed habitats has implications for conservation of these fungi. However, it is acknowledged that the data for fungal diversity and distribution is incomplete and fragmentary.     

三种松树内生真菌的分离鉴定及其对红脂大小蠹伴生真菌的拮抗作用

【背景】松树的内生真菌会影响红脂大小蠹及其伴生真菌的生长及扩散,从而影响红脂大小蠹的入侵。【目的】掌握赤峰地区红脂大小蠹寄主树种内生真菌的物种多样性,筛选对其伴生菌有拮抗作用的菌株,为红脂大小蠹的生物防治提供资源。【方法】采用组织分离法、形态学鉴定和internal transcribed spacer (ITS)序列分析相结合的方法对红脂大小蠹寄主树种油松、樟子松和潜在寄主落叶松进行内生真菌多样性研究,并用两点对峙法进行拮抗菌株筛选。【结果】松树内生真菌鉴定为2门6纲10目18科19属,其中落叶松韧皮部分离到的内生真菌数量最多,为39株,隶属于9属12种,真菌检出率为43.33%;油松次之,为30株,隶属于7属8种,真菌检出率为33.33%;樟子松最少,为29株,隶属于10属13种,真菌检出率为32.22%。3个树种的内生真菌相似性较低,无共有的菌种,青霉属(Penicillium)和篮状菌属(Talaromyces)是唯二的共有菌属,且青霉属在3个树种中均为优势菌属。平板对峙结果表明90%以上的树木内生真菌均能够与伴生真菌形成稳定的对峙,抑制率在50%-86%之间,且Phialocephala sp.和Pochonia bulbillosa对伴生菌的抑制率能高达93.7%。【结论】松树韧皮部的内生真菌具有较高的生防潜力,Phialocephala sp.和P. bulbillosa对红脂大小蠹伴生菌有较好的抑制效果,可作为红脂大小蠹的生防资源。     

The broad-scale distribution of microfungi in the Windmill Islands region, continental Antarctica

Microfungi were isolated from soils, mosses, algae and lichens in the Windmill Islands region of Antarctica. From a total of 1,228 isolates, 22 genera were identified. The most frequently isolated fungi from mosses were Mycelia sterilia (47% of total isolates), Phoma spp. (18%), Penicillium spp. (11%), Chrysosporium spp. (7%) and Thelebolus microsporus (6%). Mycelia sterilia, Penicillium spp., Mortierella spp., Chrysosporium cf. pannorum and Thelebolus microsporus were also frequently isolated from algae. Fungal distribution and diversity were poor in samples of lichens, compared to samples from mosses and algae. The frequency of occurrence of microfungi was most often associated with strong biotic influence. There was a marked increase in fungal diversity in human-disturbed sites. Twelve taxa were restricted to soils from near the Australian Casey Station, suggesting significant introduction of fungi into this environment by human activities. Away from the station, fungal distribution appeared to be related to substrata and nutrient status rather than dispersal opportunities. Suggestions for future research and the need for constant monitoring to clarify the role of human disturbance on Antarctic fungi are discussed. Received: 1 April 1997 / Accepted: 17 August 1997     

罗汉果内生真菌多样性研究

该文采用传统形态学方法结合r DNA-ITS序列分析,对我国重要药用植物罗汉果中的内生真菌进行了鉴定并研究其多样性。结果表明:采用组织培养法从罗汉果健康植株中共分离得到150株内生真菌,包括罗汉果中雌株的内生真菌96株、雄株的内生真菌54株。122株内生真菌经形态学结合r DNA-ITS序列分析鉴定为9个属,均归属为子囊菌门,包含座囊菌纲(Dothideomycetes)和子囊菌纲(Sordariomycetes)。其中,座囊菌纲(Dothideomycetes)真菌包含3科、3属;子囊菌纲(Sordariomycetes)真菌包含6科、6属。优势属为刺盘孢属(Colletotrichum)和镰刀菌属(Fusarium)。罗汉果雌、雄植株不同组织中内生真菌的定殖率及分离率的变化规律均不相同,雌株中以根中内生真菌的定殖率和分离率最高,叶片中的最低;在雄株中以叶片中的定殖率和分离率最高,根中的最低。不同菌株在雌、雄两种植株的不同组织中的分布均不同,结合内生真菌群落组成的相似性比较结果,表明部分内生真菌对罗汉果雌株和雄株,以及同一植株中的不同组织均具有偏好性。不同组织中内生真菌的多样性指数在...     

Comparison of root-associated communities of native and non-native ectomycorrhizal hosts in an urban landscape

Non-native tree species are often used as ornamentals in urban landscapes. However, their root-associated fungal communities remain yet to be examined in detail. Here, we compared richness, diversity and community composition of ectomycorrhizosphere fungi in general and ectomycorrhizal (EcM) fungi in particular between a non-native Pinus nigra and a native Quercus macrocarpa across a growing season in urban parks using 454-pyrosequencing. Our data show that, while the ectomycorrhizosphere community richness and diversity did not differ between the two host, the EcM communities associated with the native host were often more species rich and included more exclusive members than those of the non-native hosts. In contrast, the ectomycorrhizosphere communities of the two hosts were compositionally clearly distinct in nonmetric multidimensional ordination analyses, whereas the EcM communities were only marginally so. Taken together, our data suggest EcM communities with broad host compatibilities and with a limited numbers of taxa with preference to the non-native host. Furthermore, many common fungi in the non-native Pinus were not EcM taxa, suggesting that the fungal communities of the non-native host may be enriched in non-mycorrhizal fungi at the cost of the EcM taxa. Finally, while our colonization estimates did not suggest a shortage in EcM inoculum for either host in urban parks, the differences in the fungi associated with the two hosts emphasize the importance of using native hosts in urban environments as a tool to conserve endemic fungal diversity and richness in man-made systems.     

Interactions between functionally diverse fungal mutualists inconsistently affect plant performance and competition

Plants form mutualistic relationship with a variety of belowground fungal species. Such a mutualistic relationship can enhance plant growth and resistance to pathogens. Yet, we know little about how interactions between functionally diverse groups of fungal mutualists affect plant performance and competition. We experimentally determined the effects of interaction between two functional groups of belowground fungi that form mutualistic relationship with plants, arbuscular mycorrhizal (AM) fungi and Trichoderma, on interspecific competition between pairs of closely related plant species from four different genera. We hypothesized that the combination of two functionally diverse belowground fungal species would allow plants and fungi to partition their symbiotic relationships and relax plant–plant competition. Our results show that: 1) the AM fungal species consistently outcompeted the Trichoderma species independent of plant combinations; 2) the fungal species generally had limited effects on competitive interactions between plants; 3) however, the combination of fungal species relaxed interspecific competition in one of the four instances of plant–plant competition, despite the general competitive superiority of AM fungi over Trichoderma. We highlight that the competitive outcome between functionally diverse fungal species may show high consistency across a broad range of host plants and their combinations. However, despite this consistent competitive hierarchy, the consequences of their interaction for plant performance and competition can strongly vary among plant communities.     

Host Associations Between Fungal Root Endophytes and Boreal Trees

Fungal root endophytes colonize root tissue concomitantly with mycorrhizal fungi, but their identities and host preferences are largely unknown. We cultured fungal endophytes from surface-sterilized Cenococcum geophilum ectomycorrhizae of Betula papyrifera, Abies balsamea, and Picea glauca from two boreal sites in eastern Canada. Isolates were initially grouped on the basis of cultural morphology and then identified by internal transcribed spacer ribosomal DNA sequencing or by PCR restriction fragment length polymorphism. Phylogenetic analysis of the sequence data revealed 31 distinct phylotypes among the isolates, comprising mainly members of the ascomycete families Helotiaceae, Dermateaceae, Myxotrichaceae, and Hyaloscyphaceae, although other fungi were also isolated. Multivariate analyses indicate a clear separation among the endophyte communities colonizing each host tree species. Some phylotypes were evenly distributed across the roots of all three host species, some were found preferentially on particular hosts, and others were isolated from single hosts only. The results indicate that fungal root endophytes of boreal trees are not randomly distributed, but instead form relatively distinct assemblages on different host tree species.     

Evidence for specificity to Glomus group Ab in two Asian mycoheterotrophic Burmannia species

Nonphotosynthetic mycorrhizal plants, so‐called mycoheterotrophic plants, have long attracted the curiosity of botanists and mycologists. Recent advances in molecular methods based on fungal‐specific PCR amplification have dramatically enhanced the identification of their host mycorrhizal fungi. However, studies investigating the fungal hosts of arbuscular mycorrhizae‐forming mycoheterotrophs are still limited in Asia, which is known as one of the diversity hot spots of mycoheterotrophs that parasitize arbuscular mycorrhizae (AM). Therefore, we aimed to reveal the mycorrhizal associations of two Asian, fully mycoheterotrophic Burmannia species by molecular identification. Sequences of the small subunit ribosomal DNA showed that both Burmannia species are associated with several distinct lineages of Glomus group Ab. Because Glomus group Ab fungi have been confirmed as fungal hosts of various mycoheterotrophic plants in Africa and South America, we suggest they are widely exploited by AM‐forming mycoheterotrophs globally.     

Evolution of host breadth in broad interactions: mycorrhizal specificity in East Asian and North American rattlesnake plantains (Goodyera spp.) and their fungal hosts

Host breadth is often assumed to have no evolutionary significance in broad interactions because of the lack of cophylogenetic patterns between interacting species. Nonetheless, the breadth and suite of hosts utilized by one species may have adaptive value, particularly if it underlies a common ecological niche among hosts. Here, we present a preliminary assessment of the evolution of mycorrhizal specificity in 12 closely related orchid species (genera Goodyera and Hetaeria) using DNA‐based methods. We mapped specificity onto a plant phylogeny that we estimated to infer the evolutionary history of the mycorrhiza from the plant perspective, and hypothesized that phylogeny would explain a significant portion of the variance in specificity of plants on their host fungi. Sampled plants overwhelmingly associated with genus Ceratobasidium, but also occasionally with some ascomycetes. Ancestral mycorrhizal specificity was narrow in the orchids, and broadened rarely as Goodyera speciated. Statistical tests of phylogenetic inertia suggested some support for specificity varying with increasing phylogenetic distance, though only when the phylogenetic distance between suites of fungi interacting with each plant taxon were taken into account. These patterns suggest a role for phylogenetic conservatism in maintaining suits of fungal hosts among plants. We stress the evolutionary importance of host breadth in these organisms, and suggest that even generalists are likely to be constrained evolutionarily to maintaining associations with their symbionts.     

THE EVOLUTION OF PARASITISM IN THE RED ALGAE: MOLECULAR COMPARISONS OF ADELPHOPARASITES AND THEIR HOSTS1

In several groups of parasites including insect, flowering plant, fungal, and red algal parasites, morphological similarities of the parasites and their specific hosts have led to hypotheses that these parasites evolved from their hosts. But these conclusions have been criticized because the morphological features shared by parasite and host may be the result of convergent evolution. In this study, we examine the hypothesis, originally put forth by Setchell, that adelphoparasitic red algae, that is, parasitic red algae that are morphologically very similar to their hosts, evolved from their specific red algal hosts. Rather than comparing morphological features of parasites and hosts, small-subunit 18S nuclear ribosomal DNA and the internal transcribed spacer regions (ITSs) of the nuclear ribosomal repeat are compared for five parasites, their hosts, and related nonhosts from four red algal orders. These comparisons reveal that each of these adelphoparasites has evolved either directly from the host on which it is currently found, or it evolved from some other taxon that is closely related to the modern host. The parasites Gardneriella tuberifera, Rhodymeniocolax botryoides, and probably Gracilariophila oryzoides evolved from their respective hosts Sarcodiotheca gaudichaudii, Rhodymenia pacifica, and Gracilariopsis lemaneiformis, respectively. The parasite Faucheocolax attenuata evolved from either Fauchea laciniata or Fauchea fryeana and subsequently radiated onto the other host species. Presently this parasite is found on both hosts. Lastly, some parasitic genera such as Plocamiocolax are polyphyletic in their origins. A species of Plocamiocolax from an Antarctic Plocamium cartilagineum appears to have evolved from its host whereas the common Plocamiocolax pulvinata that occurs along the west coast of North America likely evolved from Plocamium violaceum and radiated secondarily onto its present day host, Plocamium cartilagineum.     

Trade-offs between arbuscular mycorrhizal fungal competitive ability and host growth promotion in Plantago lanceolata

In this study we tested for trade-offs between the benefit arbuscular mycorrhizal (AM) fungi provide for hosts and their competitive ability in host roots, and whether this potential trade-off shifts in the presence of a plant stress (herbivory). We used three species of AM fungi previously determined to vary in host growth promotion and spore production in association with host plants. We found that these AM fungal species competed for root space, and the best competitor, Scutellospora calospora, was the worst mutualist. In addition, the worst competitor, Glomus white, was the best mutualist. Competition proved to have stronger effects on fungal infection patterns than herbivory, and competitive dominance was not altered by herbivory. We found a similar pattern in a previous test of competition among AM fungi, and we discuss the implications of these results for the persistence of the mutualism and feedbacks between AM fungi and their plant hosts.