Terrestrial Orchid Species Research Articles

Ecological distribution of terrestrial orchids in a south Brazilian Atlantic region

F. S. Rocha (rocha1403@yahoo.com.br), Programa de Po´s-Graduac ¸a˜o em Botaˆnica, Univ. Federal do Rio Grande do Sul, Av. Bento Goncalves9500, BR ˆ91.501-970, Porto Alegre, RS, Brasil. J. L. Waechter, Depto de Botanica, Univ. Federal do Rio Grande do Sul, Av. BentoGonc¸alves 9500, BR 91.501-970, Porto Alegre, RS, Brasil.Terrestrial orchids comprise a taxonomically and ecologically varied group, ranging from tropical to subpolar regions andfrom wet marshy to dry sand-dune environments. An ecological survey of these plants was performed in a natural regionof Rio Grande do Sul, south Brazil, namely the northern coastal plain, between the abrupt slopes of the Serra Geral andthe coastal line of the Atlantic Ocean (29801?Sto30800?S, 49843?Wto50816?W). The study area presents a humidsubtropical climate of the Cfa type. Mean annual temperature and precipitation range from 17.5 to 20.08C and from1200 to 1700 mm, respectively. The occurrence of indigenous terrestrial orchid species was recorded for six majorhabitats or vegetation types: bogs and marshes, peat forests, rain forests, dune forests, Butia-palm stands and coastal sand-dunes. The ecological range was defined for 39 species belonging to 23 genera, based on literature, herbarium revisionsand extensive collecting along the studied area. Species richness ranged from nine species, in both coastal dunes and palm-groves, to 17 species in peat forests. A negative correlation was observed between species richness and ecological range,showing a general tendency for terrestrial orchids to be confined to one or a few habitats. Multivariate analyses indicatedlight (herbaceous vs woody vegetation) as a primary ecological factor, and soil drainage (sandy vs peaty substrates) as asecondary factor controlling terrestrial orchid distribution.

Mycorrhizal Association of Terrestrial Orchids of Cycloops Nature Reserve, Jayapura

Study on exploration of mycorrhizal association of terrestrial orchid of Cycloops Nature Reserve, Jayapura was done. Theaims of this study were to collect terrestrial orchid and to isolate orchid mycorrhiza associated with it. Survey method was used in this study. Isolation of orchid mycorrhiza was based on modified methods of Masuhara and Katsuya (1989). The result showed that there were 10 species of terrestrial orchid in this area. Eleven orchid mycorrhizal fungi were isolated from five terrestrial orchids. Among them, 6 isolates were associated with Geodorum sp. From the seventeen mycorrhizal fungi, 3 isolates were identified, namely Rhizoctonia sp., Tulasnella sp., and Ceratorhiza sp, while the last fourteen isolates have not been identified yet. Mostly, each isolate has a specific orchid host, except species G (sp. G) which associated with Phaius sp. and Plocoglottis sp.Key words: terrestrial orchid, orchid mycorrhiza, Mt. Cycloops Nature Reserve, Jayapura

Mycorrhizal status of plant species in the Chaco Serrano Woodland from central Argentina

We examined the mycorrhizal type of 128 plant species in two patches of native vegetation of the Chaco Serrano Woodland, central Argentina, the largest dry forest area in South America. Of the 128 plant species investigated (belonging to 111 genera in 53 families), 114 were colonized by arbuscular mycorrhizal fungi (AM), orchid mycorrhizal associations were present in the five terrestrial orchid species analyzed, one ectomycorrhiza was only present in Salix humboldtiana Willd., and 96 harbored a dark septate endophyte (DSE) association. Co-occurrence of AM and DSE was observed in 88 plant species. We determine morphological types of arbuscular mycorrhizal fungi (Arum, Paris, and intermediate AM structures) and report the mycorrhizal status in 106 new species, 12 of which are endemic to central Argentina and two, Aa achalensis Schltr. and Buddleja cordobensis Griseb., are declared to be vulnerable species. Root colonization in the Chaco Serrano Woodland is widespread and should be considered in revegetation programs due to the deterioration of this particular ecosystem. Considering the predominance of AM and DSE associations and the various potential benefits that these associations may bring to plant establishment, they should receive special attention in conservation and reforestation of these woodlands.

Do ambush predators prefer rewarding or non-rewarding orchid inflorescences?

Previous research has shown that the presence of a reward on average doubles reproductive success in orchids by correspondingly increasing the frequency of pollinator visitations. We examined whether such reward-induced increases have a downstream effect on the behaviour of ambush predators concealed in orchid inflorescences, extending observations begun at Downe by Charles Darwin. Specifically, we studied three orchid-rich sites in southern England, in order to compare the occurrence of crab spiders on three coexisting species of terrestrial orchids: the nectariferous Gymnadenia conopsea versus the nectar-less Dactylorhiza fuchsii and Anacamptis pyramidalis. No significant difference was observed between rewarding and non-rewarding inflorescences at Risborough, whereas at Aston Clinton the nectar-less species supported significantly more crab spiders, albeit mainly in relatively short grass. Comparison of the two non-rewarding species present at Downe approximated a significant preference by the spiders for Anacamptis, which more closely resembles the rewarding Gymnadenia. The presence of a floral reward does not result in a higher frequency of crab spiders. We speculate that concealment quality of the inflorescence, the nature of the dominant pollinator(s), and/or ease of movement of spiders between inflorescences may be more important than frequency of visits by potential prey, particularly when no other form of concealment is readily available.

Surprisingly high orchid diversity in travertine and forest areas in the Huanglong valley, China, and implications for conservation

The presence of such a large number of terrestrial orchid species in a small area (ca. 1 km2) of the Huanglong valley in southwestern China is uncommon for this country. Studying the relationship between the distribution patterns of these orchid species and their microenvironments may help us understand this uncommon phenomenon. We established 662 1 m × 1 m plots, measured the cover of each species and found that there were 33 orchid species distributed mainly in two different habitats, i.e. travertine areas and forest. In the travertine areas, 30 orchid species were found; the six most common ones being Cypripedium bardolphianum, Cypripedium flavum, Cypripedium tibeticum, Galearis diantha, Ponerorchis chusua and Phaius delavayi. However in the forested habitat, we found 21 orchid species; the most common ones being Tipularia szechuanica and Goodyera repens. Travertine areas had a higher number of orchid species as well as higher numbers of orchid species per plot as compared to forest. Light availability seems critical to the performance and distribution of orchid species. Stream flow through the travertine area during the orchids growing season appears to be an important factor in shaping and maintaining stable microenvironments favorable to the growth and reproduction of orchids. The results presented in this study suggest that some orchid species in the travertine area might be threatened if the travertine stream flows were to change or be disrupted.

Pterostylis nutans (Orchidaceae) has a specific association with two Ceratobasidium root-associated fungi across its range in eastern Australia

In this study, we have identified the root-associated fungi of a common species of terrestrial orchid across its range in eastern Australia. We have amplified and cloned fungal ITS DNA extracted from roots of 15 Pterostylis nutans R. Br. plants from six separate geographic localities. Sequencing and GenBank comparison demonstrated two species of Ceratobasidium fungi as the main fungal partners of the orchid. Uncommon fungal associates included homobasidiomycete species such as a Gymnomyces sp. and a Tricholoma sp., Leptodontidium orchidicola, and an unidentified soil fungus. These results demonstrate that specificity for fungal partners occurs in P. nutans and reinforces the idea that conservation measures for endangered Australian orchids must include ex situ perpetuation of fungal symbionts as well as plant material.

<i>Pterostylis nutans</i> (Orchidaceae) has a specific association with two <i>Ceratobasidium</i> root-associated fungi across its range in eastern Australia

In this study, we have identified the root-associated fungi of a common species of terrestrial orchid across its range in eastern Australia. We have amplified and cloned fungal ITS DNA extracted from roots of 15 Pterostylis nutans R. Br. plants from six separate geographic localities. Sequencing and GenBank comparison demonstrated two species of Ceratobasidium fungi as the main fungal partners of the orchid. Uncommon fungal associates included homobasidiomycete species such as a Gymnomyces sp. and a Tricholoma sp., Leptodontidium orchidicola, and an unidentified soil fungus. These results demonstrate that specificity for fungal partners occurs in P. nutans and reinforces the idea that conservation measures for endangered Australian orchids must include ex situ perpetuation of fungal symbionts as well as plant material.

Symbiotic seed germination of Habenaria macroceratitis (Orchidaceae), a rare Florida terrestrial orchid

The rapid loss of native orchid habitat throughout ecologically important areas (e.g., Florida) has prompted researchers to develop appropriate plans for the propagation and reintroduction of many native orchid species. Ideally, symbiotic orchid seed germination methods are utilized in the production of orchid seedlings to be used in plant reintroduction programs. In the current study we (1) describe an efficient symbiotic seed germination protocol to germinate seeds of the rare sub-tropical terrestrial orchid Habenaria macroceratitis; (2) discuss the in vitro fungal specificity demonstrated by this species; and (3) describe the effects of three photoperiods (0/24 h, 16/8 h, 24/0 h L/D) on in vitro symbiotic seed germination of H. macroceratitis. Six fungal mycobionts were isolated from both vegetative and flowering plants of H. macroceratitis from two geographically distinct sites. Symbiotic seed germination percent was highest (65.7%) and protocorm development was most advanced (Stage 2) when seeds were cultured with fungal mycobiont Hmac-310. Seeds of H. macroceratitis demonstrated a degree of specificity toward fungal mycobionts isolated from plants originating from the same site where seed was collected. Continual darkness (0/24 h L/D) inhibited initial seed germination (Stage 1; 17.1%), but stimulated subsequent protocorm development (Stage 2; 53.5%). These findings will aid in developing an efficient symbiotic seed germination protocol for the conservation of this rare Florida terrestrial orchid, and may prove useful in the conservation of other sub-tropical terrestrial orchid species.

Phylogenetic relationships of Mediterranean Neottieae and Orchideae (Orchidaceae) inferred from nuclear ribosomal ITS sequences

Sequence data for the internal transcribed spacer (ITS) region of nuclear ribosomal DNA were collected from 27 terrestrial Mediterranean orchid species. These data were included in parsimony (MP) and maximum likelihood (ML) analyses. Tree topologies from the parsimony and maximum likelihood analyses were largely congruent. Both topologies shows that Neottieae are strongly supported as monophyletic (MP = 100% and ML = 86%). Within Orchideae, Dactylorhiza + Orchis + Neotinea are sister groups; the Himantoglossum + Anacamptis clase is well delimited by the cytological synapomorphy of n = 18, in both parsimony and maximum likelihood analysis; Serapias is monophyletic according to molecular evidence, though it does not exist unequivocal distinction between the tetraploid S. lingua and the remaining diploid species; section Pseudophrys of genus Ophrys is isolated, showing unequivocal morphological (type of labellum and pollination) and karyological (tetraploid species with 2n = 72) cohesion.

In situ symbiotic seed germination and propagation of terrestrial orchid seedlings for establishment at field sites

The establishment of five species of temperate terrestrial orchids (Caladenia arenicola Hopper & A.P.Brown, Diuris magnifica D.L.Jones, D. micrantha D.L.Jones, Pterostylis sanginea D.LJones & M.A.Clem. and Thelymitra manginiorum ms) in natural habitat through in situ seed sowing, or by planting of seedlings and dormant tubers, was evaluated. Seed of the Western Australian temperate terrestrial taxa, Caladenia arenicola and Pterostylis sanguinea germinated best when sown into soil inoculated with mycorrhizal fungi at field sites but failed to develop the tubers necessary for surviving summer dormancy. However, seedling survival improved when actively growing symbiotic seedlings were transferred to natural habitat during the growing season. Caladenia arenicola and P. sanguinea seedlings survived the initial transfer to field sites but only P. sanguinea survived into the second growing season. Highest survival was obtained by translocating dormant tubers of C. arenicola and Diuris magnifica, with D. magnifica persisting at the site 5 years after translocation. However, outplanted C. arenicola survived for only 2 years. In another trial, where seedlings and dormant tubers of a rare orchid Thelymitra manginiorum were translocated into eucalypt woodland, 18% persisted after 5 years. The rare orchid D. micrantha exhibited the highest survival rates, with greater than 80% of tubers surviving 5 years after transfer of mature dormant tubers to field sites. This study highlights the benefit of using optimised methods for seedling production by symbiotic germination and nursery growth to produce advanced seedlings or dormant tubers to maximise the survival of translocated plants. It also demonstrates the need to consider different strategies when dealing with individual species.

ITS-RFLP and sequence analysis of endophytes from Acianthus, Caladenia and Pterostylis (Orchidaceae) in southeastern Queensland

We used ITS-RFLP and sequence analysis to determine the identities of the fungal endophytes of six terrestrial orchid species from southeastern Queensland, a region previously unexplored in this context. Pure cultures of orchid--colonising fungi were obtained and fungal identities were assessed by means of ITS-PCR, RFLP analysis, sequence comparison, and protocorm colonisation tests. ITS-PCR and RFLP analysis resulted in five main groupings. Sequencing and GenBank comparison of these five groups showed that the fungal endophytes isolated from the three Pterostylis species were probably Thanatephorus species. There was close sequence identity (90%) of the fungus isolated from Acianthus spp. to Epulorhiza repens, suggesting these may be the same fungal species. However, that only E. repens succeeded in colonising protocorms of Thelymitra pauciflora suggests these may be different species of Epulorhiza. Analysis of the ITS and LSU sequences of the fungus isolated from Caladenia carnea showed high identities with a sequence from a Sebacina vermifera originally isolated from Caladenia dilatata. These results show that there is specificity for fungal partners within the orchid genera Acianthus, Caladenia and Pterostylis.

Species diversity and flowering phenology of Orchidaceae in Huanglong Valley, Sichuan

China has rich terrestrial orchid resources,with the number of terrestrial orchid species equal nearly to that of epiphytic orchids. From a conservation perspective,the Chinese terrestrial orchids deserve considerable attention. Considering the huge areas of the temperate zone and alpine mountains of China,where most terrestrial orchids are distributed,and the different abundance of terrestrial orchids in different areas and different habitats,it is important to identify “hotspots” for the conservation of the Chinese terrestrial orchids. Huanglong Valley,at an elevation of 3100–3569 m and only 3.5 km long,is the main landscape feature of Huanglong Nature Reserve, Sichuan, China. It is also the largest travertine region in the world. In this narrow valley rich terrestrial orchid diversity was found: a total of 30 orchid species in 19 genera were found in the valley,all of which were terrestrial orchids,including 4 saprophytic orchids. These orchids grew in two different habitats: one was open shrub and forest margin with travertine stream flows,where 20 orchid species occurred; another was relatively dense mixed coniferous broad-leaved forest without water flows,where 10 orchid species were found. Cypripedium flavum,C. tibeticum,C. bardolphianu,Orchis chusua,O. diantha and Calanthe delavayi were the main orchid species found in Huanglong Valley with abundant individuals. The florescence times of these terrestrial orchids overlapped because of the short growing season of the alpine mountains. However,there were rich intraspecific variations in floral morphology in some orchid species. Huanglong Valley could be considered one of the terrestrial orchid “hotspots” in China,and even in the world. We believe our study results could supply basic data for generating specific management strategies,long-term monitoring and study of terrestrial orchids in Huanglong Valley.

Highly sensitive DNA fingerprinting of orchid pollinaria remnants using AFLP

Numerous Australian terrestrial orchid species in the genus Diuris may be pollinated by food source mimicry. In our field studies, direct observations of orchid–pollinator interactions were rare, but native bees were frequently captured carrying orchid pollinaria, or pollinaria remnants. Sometimes, pollinaria remnants were minimal and included only the viscidium, a sticky pad that was often highly persistent. Confirmation of such tissue as being of orchid source, and attributing them to a particular species can aid pollination studies. DNA-based methods that may identify more or less intact orchid pollinaria are available, but extremely small and degraded samples can pose technical challenges. We have developed an AFLP protocol for such difficult samples that offers some significant advantages over direct PCR-based analysis. We simulated AFLP profiling of very low-DNA samples using DNA template from serial dilutions. A DNA sample range from 6.4 picograms to at least as high as 100 nanograms (15 500-fold range) all yielded AFLP fingerprints. The practical application of this inherent sensitivity of AFLP is demonstrated by the identification of remnants of orchid pollinaria sampled from bees, presented here as a case study. It is expected that this approach will find many applications where sample DNA is limiting, or possibly where pollen of similar appearance may comprise species mixtures.

Corrigendum to: Highly sensitive DNA fingerprinting of orchid pollinaria remnants using AFLP

Numerous Australian terrestrial orchid species in the genus Diuris may be pollinated by food source mimicry. In our field studies, direct observations of orchid.pollinator interactions were rare, but native bees were frequently captured carrying orchid pollinaria, or pollinaria remnants. Sometimes, pollinaria remnants were minimal and included only the viscidium, a sticky pad that was often highly persistent. Confirmation of such tissue as being of orchid source, and attributing them to a particular species can aid pollination studies. DNA-based methods that may identify more or less intact orchid pollinaria are available, but extremely small and degraded samples can pose technical challenges. We have developed an AFLP protocol for such difficult samples that offers some significant advantages over direct PCR-based analysis. We simulated AFLP profiling of very low-DNA samples using DNA template from serial dilutions. A DNA sample range from 6.4 picograms to at least as high as 100 nanograms (15�500-fold range) all yielded AFLP fingerprints. The practical application of this inherent sensitivity of AFLP is demonstrated by the identification of remnants of orchid pollinaria sampled from bees, presented here as a case study. It is expected that this approach will find many applications where sample DNA is limiting, or possibly where pollen of similar appearance may comprise species mixtures.

Factors affecting persistence of terrestrial orchids in wet meadows and implications for their conservation in a changing agricultural landscape

We examined the occurrence of Dactylorhiza majalis, the most abundant terrestrial orchid species growing in rapidly disappearing wet meadows, at 50 historical sites for 3 years. We aimed to find the most frequent reasons for its recent extinction at many sites. We found that the main reasons for its extinction were absence of mowing, intensive fertilisation and washouts of fertilisers from fields nearby. At extant sites, we studied its biometric characteristics and composition of surrounding vegetation, to determine factors affecting its persistence. Bad performance of persisting populations of this species was associated with prevalence of grasses, low May temperatures and absence of mowing. This confirms, at metapopulation level, what has previously been observed at the level of individual populations. We suggest that the system of agricultural subsidies in the country should change towards more sensitive allocation of funds to those farmers, who will adopt the appropriate management of wet meadows and their surroundings.

Molecular phylogenetics and evolution of Orchidinae and selected Habenariinae (Orchidaceae)

Internal transcribed spacer (ITS nuclear rDNA) data have been obtained from 190 terrestrial orchid species, encompassing all genera and the great majority of the widely recognized species of Orchidinae, a heterogeneous selection of species of Habenariinae, and single species of Satyriinae and Disinae (the latter serving as outgroup). The resulting parsimony-based phylogeny reveals 12 well-resolved clades within the Orchidinae, based on Anacamptis s.l., Serapias, Ophrys, Steveniella–Himantoglossum s.l. (including ‘Comperia’ and ‘Barlia’, most species being 2n = 36), Neotinea s.l., Traunsteinera–Chamorchis, Orchis s.s., Pseudorchis–Amerorchis–Galearis–Neolindleya–Platanthera s.l. (most 2n = 42), Dactylorhiza s.l., Gymnadenia s.l. (most 2n = 40, 80), Ponerorchis s.l.–Hemipilia s.l.–Amitostigma–Neottianthe, and Brachycorythis (most 2n = 42). Relationships are less clearly resolved among these 12 clades, as are those within Habenariinae; the subtribe appears either weakly supported as monophyletic or as paraphyletic under maximum parsimony, and the species-rich genus Habenaria is clearly highly polyphyletic. The triphyly of Orchis as previously delimited is confirmed, and the improved sampling allows further generic transfers to Anacamptis s.l. and Neotinea s.l. In addition, justifications are given for: (1) establishing Steveniella as the basally divergent member of an appreciably expanded Himantoglossum that incorporates the former genera ‘Barlia’ and ‘Comperia’, (2) reuniting ‘Piperia’ with a broadly defined Platanthera as section Piperia, necessitating ten new combinations, (3) broadening Ponerorchis to include Chusua, and Hemipilia to include single ‘orphan’ species of Ponerorchis and Habenaria, and (4) recognizing ‘Gymnadenia’camtschatica as the monotypic Neolindleya camtschatica within the Pseudorchis∼Platanthera clade. Few further generic transfers are likely in Orchidinae s.s., but they are anticipated among habenariid genera, on acquisition of additional morphological and molecular evidence; one probable outcome is expansion of Herminium. Species-level relationships are also satisfactorily resolved within most of the major clades of Orchidinae, with the notable exceptions of Serapias, the derived sections of Ophrys, Himantoglossum s.s., some sections within Dactylorhiza, the former genus ‘Nigritella’ (now tentatively placed within Gymnadenia s.l.), Hemipilia s.l., and possibly Ponerorchis s.s. Relationships among the 12 major clades broadly accord with bona fide records of intergeneric hybridization. Current evidence supports the recently recognized 2n = 36 clade; it also indicates a 2n = 40 clade that is further diagnosed by digitate root-tubers, and is derived relative to the recently recognized clade of exclusively Asian genera (Ponerorchis s.l.–Hemipilia s.l.–Amitostigma–Neottianthe). This in turn appears derived relative to the Afro-Asiatic Brachycorythis group; together, these two clades identify the plesiomorphic chromosome number as 2n = 42. If the African genus Stenogolottis is correctly placed as basally divergent within a monophyletic Habenariinae, the tribe Orchideae and subtribes Orchidinae and Habenariinae could all have originated in Africa, though in contrast the Asiatic focus of the basally divergent members of most major clades of Orchidinae suggests an Asiatic radiation of the subtribe. Morphological characters informally ‘mapped’ across the molecular phylogeny and showing appreciable levels of homoplasy include floral and vegetative pigmentation, flower shape, leaf posture, gynostemium features, and various pollinator attractants. Qualitative comparison of, and reciprocal illumination between, degrees of sequence and morphological divergence suggests a nested set of radiations of progressively decreasing phenotypic magnitude. Brief scenarios, both adaptive and non-adaptive, are outlined for specific evolutionary transitions. Recommendations are made for further species sampling, concentrating on Asian Orchidinae (together with the Afro-Asiatic Brachycorythis group) and both Asian and Southern Hemisphere Habenariinae, and adding plastid sequence data. Taxonomic changes listed are: Anacamptis robusta (T.Stephenson) R.M.Bateman, comb. nov., A. fragrans (Pollini) R.M.Bateman, comb. nov., A. picta (Loiseleur) R.M.Bateman, comb. nov., Neotinea commutata (Todari) R.M.Bateman, comb. nov., N. conica (Willdenow) R.M.Bateman, comb. nov., Platanthera elegans Lindley ssp. maritima (Rydberg) R.M.Bateman, comb. nov., P. elegans Lindley ssp. decurtata (R.Morgan & Glicenstein) R.M.Bateman, comb. nov., P. elongata (Rydberg) R.M.Bateman, comb. nov., P. michaelii (Greene) R.M.Bateman, comb. nov., P. leptopetala (Rydberg) R.M.Bateman, comb. nov., P. transversa (Suksdorf) R.M.Bateman, comb. nov., P. cooperi (S.Watson) R.M.Bateman, comb. nov., P. colemanii (R.Morgan & Glicenstein) R.M.Bateman, comb. nov., P. candida (R.Morgan & Ackerman) R.M.Bateman, comb. nov. and P. yadonii (R.Morgan & Ackerman) R.M.Bateman, comb. nov. © 2003 The Linnean Society of London, Botanical Journal of the Linnean Society, 2003, 142, 1–40.

Seasonal development of annual shoots in some terrestrial orchids from Russia and Japan

AbstractAnnual shoots of 46 terrestrial orchid species commonly found in wide ranges of temperate climates in Russia and Japan change their patterns of growth recurrence from the dormancy state, through formation and growth, to the next dormancy state during the course of yearly response to seasonal cycles of environmental conditions. Each of the species has its own strategy in seasonal development of aerial shoots, rhizomes, tubers and roots, and shows seasonal differentiation of shoot morphogenesis at the early stage of new shoot apex formation in accordance with its growth habit, habitat and range size of geographical distribution. Perennial orchids with sympodial growth patterns and primitive life forms are characterized by long duration of shoot and inflorescence development inside the bud. Among the species studied, the orchids that have annually regenerating root‐stem tubers have the shortest duration of root and shoot morphogenesis. The species that have predominant patterns of monopodial growth show variability in duration of lateral shoot growth due to the energy budget of the mother plant. The species which have latitudinally long ranges of distribution from northern colder regions to southern warmer regions tend to take longer for shoot development inside the bud, and aerial shoots have a shorter life‐span in the northern regions than those in the south.

Characterization and Taxonomic Placement of Rhizoctonia-like Endophytes from Orchid Roots

Twenty-one Rhizoctonia-like fungal strains were isolated from the roots of four terrestrial orchid species from various locations in Hong Kong. The cultural morphology, nuclear number of the hyphal cell, pore ultrastructure, and RAPD and CAPS analyses of rDNA fragments revealed that most of these isolates were associated with the genera Ceratorhiza and Epulorhiza. RAPD analysis showed the presence of genetic diversity between the isolates from different hosts and locations. The compatibility between a selection of these Ceratorhiza and Epulorhiza isolates and 14 orchid species was determined using a symbiotic germination method. The germination and development of three orchid species, Arundina chinensis, Spathoglottis pubescens, and Spiranthes hongkongensis, were strongly stimulated by the Epulorhiza isolates. Habenaria dentata was found to form symbionts successfully with a Ceratorhiza isolate.

Characterization and taxonomic placement of Rhizoctonia-like endophytes from orchid roots

Twenty-one Rhizoctonia-like fungal strains were isolated from the roots of four terrestrial orchid species from various locations in Hong Kong. The cultural morphology, nuclear number of the hyphal cell, pore ultrastructure, and RAPD and CAPS analyses of rDNA fragments revealed that most of these isolates were associated with the genera Ceratorhiza and Epulorhiza. RAPD analysis showed the presence of genetic diversity between the isolates from different hosts and locations. The compatibility between a selection of these Ceratorhiza and Epulorhiza isolates and 14 orchid species was determined using a symbiotic germination method. The germination and development of three orchid species, Arundina chinensis, Spathoglottis pubescens, and Spiranthes hongkongensis, were strongly stimulated by the Epulorhiza isolates. Habenaria dentata was found to form symbionts successfully with a Ceratorhiza isolate.

Response to paclobutrazol of symbiotic mycorrhizal fungi and dropper (tuber stalk) formation of host orchid seedlings

The effects of the triazole compound paclobutrazol on the mycorrhizalfungi and production of droppers (tuber stalks) in three species of terrestrialorchids of southwestern Australia were investigated. Seedlings ofDiuris laxiflora Lindley (bee orchid), Microtismedia R. Br. (common mignonette orchid), and Pterostylissanguinea D. Jones & M. Clements (dark banded greenhood orchid)were cultured symbiotically with specific mycorrhizal fungi invitro. The mycorrhizal fungi of the study species were grown on mediacontaining paclobutrazol at 0, 1.7, 3.4, 10.2, or 17.0 μM(corresponding to 0, 0.5, 1.0, 3.0, or 5.0 mgL−1). Paclobutrazol at all concentrations evaluateddecreased the growth rates of the mycorrhizal fungi of M.media and P. sanguinea below that of thecontrol. However, paclobutrazol did not adversely affect the growth of themycorrhizal fungus of D. laxiflora, and low concentrations(1.7 or 3.4 μM) stimulated the growth of this fungus. Symbiotic seedlings of the study species were exposed to paclobutrazolat 0, 1.7, 3.4, 10.2, or 17.0 μM. Paclobutrazol at allconcentrations evaluated increased dropper (tuber stalk) production inD. laxiflora, but had no effect on M.media and P. sanguinea. This suggests that, for species in which paclobutrazol has no fungicidaleffect on mycorrhizal fungi, it has the potential to stimulate early andefficient tuberization of symbiotic orchid seedlings.