The early-stage ectomycorrhizal Thelephoroid fungal sp. is competitive and effective on<Emphasis Type="Italic"> Afzelia africana</Emphasis> Sm. in nursery conditions in Senegal

This study was conducted to evaluate the competitiveness and effectiveness of Thelephoroid fungal sp. ORS.XM002 against native ectomycorrhizal fungal species colonizing potted Afzelia africana seedlings during 3 months of growth in different forest soils collected from under mature trees. Using morphotyping and restriction fragment length polymorphism (RFLP) analysis of the nuclear rDNA internal transcribed spacer (ITS), we were able to distinguish the introduced Thelephoroid fungal sp. ORS.XM002 among native ectomycorrhizal fungal species that form ectomycorrhizae in A. africana seedlings. The morphotype (MT) of the introduced fungus showed some color variation, with a shift from light- to dark-brown observed from younger to older mycorrhizal tips. We were able to differentiate the ITS type xm002 of the introduced fungus from the 14 ITS-RFLP types characterizing the 9 native MT that occurred in forest soils. The frequency of ITS type xm002 ranged from 40% to 49% depending on the forest soil used, and was always higher than those of ITS types from native dark-brown MT that occurred in inoculated seedlings 3 months after inoculation. We considered Thelephoroid fungal sp. ORS.XM002 to be responsible for stimulation of mycorrhizal colonization of inoculated A. africana seedlings when compared with control seedlings in forest soils. This fungus appeared to be more effective in increasing the root dry weight of A. africana seedlings. To identify the unknown introduced fungal species and native MT, we sequenced the ML5/ML6 region of the mitochondrial large subunit rRNA. Sequence analysis showed that these fungi belong to three ML5/ML6 groups closely related to the Cortinarioid, Thelephoroid, and Sclerodermataceous taxa. The molecular evidence for the persistence of Thelephoroid fungal sp. ORS.XM002 despite competition from native fungi argues in favor of using this fungus with A. africana in nursery soil conditions in Senegal.     

Mycorrhizal synthesis of four ectomycorrhizal fungi in potted <Emphasis Type="Italic">Populus maximowiczii</Emphasis> seedlings

Ectomycorrhizal (ECM) syntheses between four ECM fungi, Laccaria amethystina, Hebeloma mesophaeum, Thelephora terrestris, and Tomentella sp., and Populus maximowiczii seedlings that are known to form ECM at a denuded area of Mt. Usu were performed in volcanic debris in a controlled growth chamber. The percentage of ECM colonization and seedling growth were determined 3 months after inoculation. Seedlings were successfully colonized by the inoculated ECM fungi with low contamination ratios. Seedling height and biomass were larger in the inoculated seedlings than in the control, although the effects of inoculation on seedling growth varied with the ECM fungus.     

Contrasting responses to ectomycorrhizal inoculation in seedlings of six tropical African tree species

Five caesalpinioid legumes, Afzelia africana, Afzelia bella, Anthonotha macrophylla, Cryptosepalum tetraphylum and Paramacrolobium coeruleum, and one Euphorbiaceae species, Uapaca somon, with a considerable range in seed sizes, exhibited different responses to inoculation by four species of ectomycorrhizal (ECM) fungi, Scleroderma dictyosporum, S. verrucosum, Pisolithus sp. and one thelephoroid sp. in greenhouse conditions. Thelephoroid sp. efficiently colonized seedlings of all of the five caesalpinioid legumes except U. somon, but provided no more growth benefit than the other fungi. Thelephoroid sp. and S. dictyosporum colonized seedlings of U. somon poorly, but stimulated plant growth more than the other fungi. The relative mycorrhizal dependency (RMD) values of the caesalpinioid legumes were never higher than 50%, whilst U. somon had RMD values ranging from 84.6 to 88.6%, irrespective of the fungal species. The RMD values were negatively related to seed mass for all plant species. Potassium concentrations in leaves were more closely related than phosphorus to the stimulation of seedling biomass production by the ECM fungi. Our data support the hypothesis that African caesalpinioid legumes and euphorbe tree species with smaller seeds show higher RMD values than those with the larger seeds.     

Ectomycorrhizal fungi associated with Pinus sylvestris seedlings respond differently to increased carbon and nitrogen availability: implications for ecosystem responses to global change

The ectomycorrhizal (ECM) symbiosis can cause both positive and negative feedback with trees under elevated CO₂. Positive feedback arises if the additional carbon (C) increases both nutrient uptake by the fungus and nutrient transfer to the plant, whereas negative feedback results from increased nutrient uptake and immobilization by the fungus and reduced transfer to the plant. Because species of ECM fungi differ in their C and nitrogen (N) demand, understanding fungal species‐specific responses to variation in C and N supply is essential to predict impacts of global change. We investigated fungal species‐specific responses of ECM Scots pine (Pinus sylvestris) seedlings under ambient and elevated CO₂ (350 or 700 μL L⁻¹ CO₂) and under low and high mineral N availability. Each seedling was associated with one of the following ECM species: Hebeloma cylindrosporum, Laccaria bicolor and Suillus bovinus. The experiment lasted 103 days. During the final 27 days, seedlings were labeled with ¹⁴CO₂ and ¹⁵N. Most plant and fungal parameters were significantly affected by fungal species, CO₂ level and N supply. Interactions between fungal species and CO₂ were also regularly significant. At low N availability, elevated CO₂ had the smallest impact on the photosynthetic performance of seedlings inoculated with H. cylindrosporum and the largest impact on seedlings with S. bovinus. At ambient CO₂, increasing N supply had the smallest impact on seedlings inoculated with S. bovinus and the largest on seedlings inoculated with H. cylindrosporum. At low N availability, extraradical hyphal length increased after doubling CO₂ level, but this was significant only for L. bicolor. At ambient CO₂, increasing N levels reduced hyphal length for both H. cylindrosporum and S. bovinus, but not for L. bicolor. We discuss the potential interplay of two major elements of global change, elevated CO₂ and increased N availability, and their effects on plant growth. We conclude that increased N supply potentially relieves mycorrhiza‐induced progressive N limitation under elevated CO₂.     

Mixotrophy of Platanthera minor, an orchid associated with ectomycorrhiza-forming Ceratobasidiaceae fungi

? We investigated the fungal symbionts and carbon nutrition of a Japanese forest photosynthetic orchid, Platanthera minor, whose ecology suggests a mixotrophic syndrome, that is, a mycorrhizal association with ectomycorrhiza (ECM)-forming fungi and partial exploitation of fungal carbon. ? We performed molecular identification of symbionts by PCR amplifications of the fungal ribosomal DNA on hyphal coils extracted from P. minor roots. We tested for a (13)C and (15)N enrichment characteristic of mixotrophic plants. We also tested the ectomycorrhizal abilities of orchid symbionts using a new protocol of direct inoculation of hyphal coils onto roots of Pinus densiflora seedlings. ? In phylogenetic analyses, most isolated fungi were close to ECM-forming Ceratobasidiaceae clades previously detected from a few fully heterotrophic orchids or environmental ectomycorrhiza surveys. The direct inoculation of fungal coils of these fungi resulted in ectomycorrhiza formation on P. densiflora seedlings. Stable isotope analyses indicated mixotrophic nutrition of P. minor, with fungal carbon contributing from 50% to 65%. ? This is the first evidence of photosynthetic orchids associated with ectomycorrhizal Ceratobasidiaceae taxa, confirming the evolution of mixotrophy in the Orchideae orchid tribe, and of ectomycorrhizal abilities in the Ceratobasidiaceae. Our new ectomycorrhiza formation technique may enhance the study of unculturable orchid mycorrhizal fungi.     

野外模拟酸雨胁迫下接种外生菌根真菌对马尾松幼苗的缓解作用

外生菌根真菌能够提高宿主植物对外界环境胁迫的抵抗力。主要探讨野外条件下外生菌根真菌对酸雨胁迫下马尾松(Pinus massoniana)幼苗生长、养分元素以及表层土壤的影响,以期为酸雨严重区马尾松林恢复提供科学依据。以2年生马尾松幼苗为材料,采用原位试验,共设置6个处理:p H5.6(对照)处理未接种、对照处理接种、p H4.5酸雨处理未接种、p H4.5酸雨处理接种、p H3.5酸雨处理未接种、p H3.5酸雨处理接种。研究表明:(1)酸雨处理与对照处理相比显著降低了非菌根苗总生物量及各部位生物量(根、茎、叶),对株高无显著影响,接种外生菌根真菌可以缓解酸雨对马尾松幼苗生长的不利影响;(2)与对照处理相比,酸雨处理的非菌根苗的针叶中N、P、Ca含量升高,Mg含量降低,根系中N、P、Ca含量降低,Mg含量随p H的降低先升高后降低。接种外生菌根真菌显著提高了p H3.5酸雨处理的马尾松幼苗根系中N、P、Ca、Mg含量,而对针叶中N、P、Ca、Mg含量无显著影响。(3)在非菌根土壤中,p H3.5酸雨处理与对照处理相比显著降低了土壤中有机质、速效磷、速效钾、可溶性碳、可溶性氮、铵态氮、硝态氮含量,而接种外生菌根真菌显著提高了上述指标。酸雨对土壤阳离子交换量无显著影响。总而言之,接种外生菌根真菌促进了酸雨处理的马尾松幼苗生长、缓解了酸雨对马尾松幼苗养分元素和表层土壤的不利影响,由此可见接种外生菌根真菌是减轻酸雨对马尾松危害的一个重要途径。     

菌丝桥在日本落叶松幼苗间磷传递和植株生长中的作用

 应用四室隔网系统研究了菌丝桥在日本落叶松(Larix kaempferi)幼苗间传递磷的作用。结果表明,供体接种卷缘桩菇(Paxillus involutus)和彩色豆马勃（Pisolithus tinctorius）后,其外延菌丝可以穿过隔离层侵染受体落叶松,在供体和受体落叶松间形成了菌丝桥。供体植株接种菌根真菌后生物量明显增加,但是对受体植株没有显著的影响。菌根真菌侵染的供体和受体植株的根、地上部吸磷量均分别显著高于对照,而且供体植株根、地上部吸磷量增加的程度明显高于受体。被卷缘桩菇和彩色豆马勃侵染的受体植株体内32P的放射性强度分别是对照的10倍和6倍,两者形成菌丝桥后传递到受体植株的32P分别为供体植株体内32P的1.10%和0.22%。供体植株吸收的32P可以通过菌丝桥传递给受体,但是绝对数量十分有限,对受体植株磷营养没有产生显著的影响,但P. involutus和P. tinctorius侵染受体植株后,促进了受体落叶松对磷的吸收,这是菌丝桥形成后,真菌帮助受体植株吸收磷引起的。     

Differential responses of three fungal species to environmental factors and their role in the mycorrhization of<Emphasis Type="Italic"> Pinus radiata</Emphasis> D. Don

Three ectomycorrhizal (ECM) isolates of Rhizopogon luteolus, R. roseolus and Scleroderma citrinum were found to differ markedly in their in vitro tolerance to adverse conditions limiting fungal growth, i.e. water availability, pH and heavy metal pollution. S. citrinum was the most sensitive, R. luteolus intermediate and R. roseolus the most tolerant species. Pinus radiata D. Don seedlings were inoculated in the laboratory and in a containerised seedling nursery with spore suspensions of the three ECM species. Colonisation percentage was considerably lower under nursery conditions, probably due to competition by native fungi. The effects of nursery ECM inoculation on seedling growth depended on the fungal species. Only R. roseolus-colonised plants showed a significantly higher shoot growth than non-mycorrhizal plants. All three fungi induced significantly higher root dry weights relative to control plants. Despite the low mycorrhizal colonisation, mycorrhization with all three species improved the physiological status of nursery-grown seedlings, e.g. enhanced root enzyme activity, shoot nutrient and pigment content, net photosynthesis rate and water use efficiency. Of the three fungal species, R. roseolus was the most effective; this species was also the most adaptable and showed the greatest range of tolerance to adverse environmental conditions in pure culture. It is, therefore, proposed as a promising fungal species for ECM inoculation of P. radiata in the nursery.     

Effect of ectomycorrhizal fungi on chestnut ink disease

 Seedlings of Castanea sativa were inoculated at transplanting time with four ectomycorrhizal (ECM) fungi, Laccaria laccata, Hebeloma crustuliniforme, H. sinapizans and Paxillus involutus. At the end of the first vegetative season, 7 months after sowing, half of the mycorrhizal and nonmycorrhizal seedlings were challenged with a zoospore suspension of Phytophthora cambivora and the other half with P. cinnamomi. Five months later, mycorrhizal plants infected with P. cambivora or P. cinnamomi showed no sign of pathogen infection. The ECM fungi increased plant biomass also in the presence of the pathogen. Mycorrhizal seedlings inoculated with the pathogens showed greater shoot and root development than nonmycorrhizal chestnut plants. All the fungi tested reduced the negative effect of the ink disease pathogens on the plant host in vivo. The mechanisms by which the ECM fungi protect chestnut seedlings are discussed. Accepted: 20 May 1999     

Management of nursery practices for efficient ectomycorrhizal fungi application in the production of Quercus ilex

The application of ectomycorrhizal (ECM) fungi on forest nursery production is regarded as part of good management practice. However, before employing large scale inoculations in a nursery the interaction between ECM symbionts, growth substrate and fertilisation input should be studied to select the most suitable nursery practices for promoting plant growth and ECM colonisation. In this study, seedlings of Quercus ilex were inoculated with Paxillus involutus, Hebeloma mesophaeum or Cenococcum geophilum and grown in three different substrates commonly used in forest nurseries: peat-based compost, forest soil or composted pine bark. The effect of various fertilisation regimes was also studied. The choice of substrate had a significant effect on plant growth and ECM colonisation. The most appropriate combination of substrate and ECM fungus for Q. ilex growth and nutrition was peat and H. mesophaeum. Plants grown on a peat-based compost and inoculated with H. mesophaeum had a significantly greater biomass and leaf phosphorus concentration without fertilisation. Composted pine bark was found not to be suitable for growth or for mycorrhization. If the appropriate growth substrate is selected, it is possible to replace the use of chemical fertilisers by inoculation with selected ECM fungi. This results in a significant increase in plant development, and thus ECM fungi can be recommended as a more environmental friendly biotechnological approach to plant management in the nursery.     

Nitrogen source effects on rhizosphere pH and nutrient accumulation by Pacific Northwest conifers

Growth responses ofCasuarina cunninghamiana to inoculation withFrankia are described in unsterilized field soils at three sites. At Mt Crawford, South Australia, seedlings of three provenances ofC. cunninghamiana were inoculated with a singleFrankia source just prior to planting out. Forty-four months after planting, inoculation had more than doubled wood production by twoC. cunninghamiana provenances, whilst a third provenance grew poorly and did not respond to inoculation. In Zimbabwe, seedlings of one provenance ofC. cunninghamiana were inoculated in the nursery with one of four differentFrankia strains. In an N deficient soil at Kadoma, three of theseFrankia increased tree height 14 months after planting by between 50% and 70% in comparison to the uninoculated seedlings. The fourthFrankia strain resulted in increased tree height to three times that of the uninoculated controls and up to double that of the other threeFrankia strains. At Gympie, Queensland, Australia, seedlings ofC. cunninghamiana raised open-rooted in a nursery bed were inoculated withFrankia seventeen weeks before planting out. During the 22 months following planting in the field, tree growth was limited by soil P status and there was no response in tree height or stem diameter to inoculation withFrankia or to N fertilizer unless P was applied. In the presence of added P there was a significant response both toFrankia inoculation and to N fertilizer. This positive interaction between P application and N treatment was reflected in wood volumes-inoculated trees and those trees supplied N fertilizer produced 34% and 95% more wood volume than did the uninoculated trees. These results demonstrate the potential to increase the productivity of Casuarina plantings by inoculation withFrankia and by alleviation of P deficiency.     

Effect of vesicular-arbuscular mycorrhizal fungi and ofagrobacterium radiobacter on maize growth

An influence of dual inoculation with the rhizosphere bacteriumAgrobacterium radiobacter, and the VAM fungi,Glomus mosseae andGlomus sp., on maize growth and mycorrhizal infection was observed. Separate inoculations of bacteria or fungi showed significant positive effects on the shoot biomass production of pot-cultured plants only at the last of three consecutive harvests. Plant biomass production was enhanced substantially after a dual inoculation with bacteria and fungi. Synergistic interaction of fungal and bacterial inoculation and growth stimulation was evident at all three harvests compared to uninoculated plants and also compared to plants inoculated with fungi or bacteria only. The dual inoculation increased the shoot biomass of plants by approximately 30% as compared with control. No significant differences were found in mycorrhizal infection between plants uninoculated and inoculated with bacteria.Agrobacterium radiobacter seems to be compatible with mycorrhizal symbiosis and can act a synergistic partner of some VAM fungi.     

Ectomycorrhizal fungi promote growth of <Emphasis Type="Italic">Shorea balangeran</Emphasis> in degraded peat swamp forests

Shorea balangeran is an important component of peat swamp forests in Southeast Asia and is an important source of timber. However, S. balangeran has been decreasing in number due to overexploitation. The objective of this study was to investigate the effect of inoculation of native ectomycorrhizal (ECM) fungi on growth of S. balangeran in degraded peat swamp forest. Spores of Boletus sp., Scleroderma sp., and Strobilomyces sp. were collected from natural peat swamp forest in Indonesia. Seedlings of S. balangeran were inoculated with or without (control) spores and grown in sterilized peat soil under nursery conditions for 6 months. Then, the seedlings were transplanted into a degraded peat swamp forest and grown for 40 months. ECM colonization was 59–67% under nursery conditions and increased shoot height and weight. Shoot height, stem diameter, and survival rates were higher in inoculated seedlings than in control 40 months after transplantation. The results suggest that inoculation of native ECM fungi onto native tree species is useful for reforestation of degraded peat swamp forests.     

Allelopathic effects of interrupted fern on northern red oak seedlings: Amelioration bySuillus luteus L.: Fr.

Summary The allelopathic effects of interrupted fern frond leachates on ectomycorrhizal (inoculated) and nonmycorrhizal (noninoculated) northern red oak (Quercus rubra L.) seedlings were investigated. Container-grown northern red oak was inoculated with vegetative mycelium ofSuillus luteus L. Fr. following acorn germination. Noninoculated control seedlings were also maintained. Seedlings were grown in a glasshouse under full sunlight or shaded (25% of full sunlight) conditions. Leachate or deionized water solutions were applied to seedlings eleven times over a 91-day period to simulate a rainfall induced transfer of allelopathic chemicals from fern fronds to the soil. Fern frond leachates significantly reduced seedling survival, however, inoculated seedlings showed less mortality. Chromium concentrations of pooled lateral root or leaf tissue were comparatively higher in tissues exhibiting greater mortality. Root biomass was reduced by fern fern frond leachate applications. Seedling biomass was not significantly affected by fungal inoculation. Our results confirm previous documentation of the allelopathic potential of ferns, and suggest that ectomycorrhizal fungi may ameliorate allelopathic effects of ferns on northern red oak seedling survival and growth.     

Mycorrhizal associations in Hong Kong Fagaceae

Castanopsis fissa Rehd. & Wils. is widely distributed from the tropics to the temperate regions of China and Japan and is an important forest component in Hong Kong. Pot-grown C. fissa seedlings inoculated with vegetative mycelial inocula of seven ectomycorrhizal fungi for 20 weeks were analysed for growth performance and mineral nutrient uptake of N, P, K and Ca. Shoot growth stimulation in all fungal treatments generally occurred in the first 4–8 weeks of seedling development. Uptake of P was generally enhanced by all fungi inoculated. Seedlings inoculated with Pisolithus tinctorius (Pers.) Coker and Couch and Cenococcum geophilm (Sow.) Fredinard et Winge, which colonized 22% and 33% of roots respectively, exhibited growth stimulation. The results indicate that P. tinctorius and C. geophilum are suitable for use in large-scale nursey inoculation.     

Mycorrhiza formation and growth of Eucalyptus globulus seedlings inoculated with spores of various ectomycorrhizal fungi

 As many eucalypts in commercial plantations are poorly ectomycorrhizal there is a need to develop inoculation programs for forest nurseries. The use of fungal spores as inoculum is a viable proposition for low technology nurseries currently producing eucalypts for outplanting in developing countries. Forty-three collections of ectomycorrhizal fungi from southwestern Australia and two from China, representing 18 genera, were tested for their effectiveness as spore inoculum on Eucalyptus globulus Labill. seedlings. Seven-day-old seedlings were inoculated with 25 mg air-dry spores in a water suspension. Ectomycorrhizal development was assessed in soil cores 65 and 110 days after inoculation. By day 65, about 50% of the treatments had formed ectomycorrhizas. By day 110, inoculated seedlings were generally ectomycorrhizal, but in many cases the percentage of roots colonized was low (<10%). Species of Laccaria, Hydnangium, Descolea, Descomyces, Scleroderma and Pisolithus formed more ectomycorrhizas than the other fungi. Species of Russula, Boletus, Lactarius and Hysterangium did not form ectomycorrhizas. The dry weights of inoculated seedlings ranged from 90% to 225% of the uninoculated seedlings by day 110. Although plants with extensively colonized roots generally had increased seedling growth, the overall mycorrhizal colonization levels were poorly correlated to seedling growth. Species of Laccaria, Descolea, Scleroderma and Pisolithus are proposed as potential candidate fungi for nursery inoculation programs for eucalypts. Accepted: 7 May 1998     

Competition for nitrogen between Pinus sylvestris and ectomycorrhizal fungi generates potential for negative feedback under elevated CO2

We investigated fungal species-specific responses of ectomycorrhizal (ECM) Scots pine (Pinus sylvestris) seedlings on growth and nutrient acquisition together with mycelial development under ambient and elevated CO₂. Each seedling was associated with one of the following ECM species: Hebeloma cylindrosporum, Laccaria bicolor, Suillus bovinus, S. luteus, Piloderma croceum, Paxillus involutus, Boletus badius, or non-mycorrhizal, under ambient, and elevated CO₂ (350 or 700 μl l⁻¹ CO₂); each treatment contained six replicates. The trial lasted 156 days. During the final 28 days, the seedlings were labeled with ¹⁴CO₂. We measured hyphal length, plant biomass, ¹⁴C allocation, and plant nitrogen and phosphorus concentration. Almost all parameters were significantly affected by fungal species and/or CO₂. There were very few significant interactions. Elevated CO₂ decreased shoot-to-root ratio, most strongly so in species with the largest extraradical mycelium. Under elevated CO₂, ECM root growth increased significantly more than hyphal growth. Extraradical hyphal length was significantly negatively correlated with shoot biomass, shoot N content, and total plant N uptake. Root dry weight was significantly negatively correlated with root N and P concentration. Fungal sink strength for N strongly affected plant growth through N immobilization. Mycorrhizal fungal-induced progressive nitrogen limitation (PNL) has the potential to generate negative feedback with plant growth under elevated CO₂. Responsible Editor: Herbert Johannes Kronzucker     

Soil inoculation of lodgepole pine seedlings alters root-associated fungal communities but does not improve seedling performance in beetle-killed pine stands

Extensive tree mortality in forests can change the community composition of soil fungi altering seedling establishment, a process critical to forest restoration. Disturbances that result in the loss of ectomycorrhizal fungi, in particular, may impede the establishment of tree species reliant on these symbionts for their survival. Inoculation of seedlings with soil from intact forests may improve the establishment of seedlings in such disturbances but the method has rarely been tested in the field. Here, we assess whether soil inoculation improves lodgepole pine (Pinus contorta var. latifolia) seedling performance in conspecific stands with high levels of tree mortality caused by a mountain pine beetle (Dendroctonus ponderosae) outbreak and whether underlying soil type modifies inoculation effects. We first inoculated seedlings in a growth chamber with small amounts of soils (5% volume) originating from either intact (<10%) or “beetle-killed” (>70% pine basal area killed) conspecific stands or added no soil inoculum and, after 4 months, transplanted them into 15 beetle-killed stands. After two growing seasons, root-associated fungal communities of seedlings receiving inoculum from intact stands differed in composition from those receiving inoculum from beetle-killed stands or no inoculum. However, inoculation had no effect on seedling survival, height, or biomass. Site properties, including soil texture and the resident fungal community composition, overwhelmed the effect of soil inoculation on seedling performance. Seedling survival and shoot mass was higher in sandy than loamy soils. Restoration to improve seedling performance in beetle-killed stands should consider stand-level treatments as soil inoculation at the level evaluated was ineffective.     

Controlled inoculation of Norway spruce (Picea abies) with Sirococcus conigenus: PCR-based quantification of the pathogen in host tissue and infection-related increase of phenolic metabolites

Controlled inoculation of spruce seedling needle crowns and of shoots of 4-year-old spruce trees by Sirococcus conigenus led to disease symptoms (discoloration and necrosis) and to the induction of phenolic metabolites. Even upon complete infection, as proved by re-isolation of the pathogen from inoculated seedlings, only 40% of the plants developed visible disease symptoms after 38 days. A Sirococcus-specific polymerase chain reaction (PCR) primer pair, SIRO1 and SIRO6, was designed based on sequences of a RAPD fragment. The primer pair permitted the detection of 1 pg fungal DNA (10-40 genomes) in 1 mg fresh weight spruce tissues (needles, bark, wood), regardless of visible disease symptoms. The amounts of the major phenolic compound of spruce needles, catechin, increased significantly in all of the five spruce provenances as a response to inoculation with Sirococcus. The second major phenolic compound, picein, increased in three of the provenances, whereas the remaining two had high concentrations to begin with and showed no reaction. Minor phenolic compounds increased in response to infection regardless of provenance. In a preliminary field study, Sirococcus infection of spruce was detectable by PCR even in the presence of massive infection by other fungi, such as Rhizospaera spp. and Lophodermium spp.     

不同种源花榈木苗期生长及生理特性比较

为了解不同种源花榈木在贵阳的生长特性和差异,该文通过对10个种源地花榈木进行育苗试验,测定其两年生实生苗的苗高、地径、生物量、叶片光合参数、光合色素、硝酸还原酶活性、硝态氮含量和根系活力,并进行差异性分析。结果表明:(1)10个种源花榈木净光合速率、气孔导度、胞间CO₂浓度、蒸腾速率和水分利用效率差异显著(P<0.05),表明不同种源花榈木光合特性及光能利用效率具有较大差异,浙江杭州和浙江永康花榈木是具有较高光合生长潜力的种源。(2)种源间的叶绿素含量、硝酸还原酶、硝态氮、根系活力存在显著差异,福建建瓯种源的叶绿素a、叶绿素b含量和叶绿素总量最高,能够将光合原初反应过程中积蓄的光能进行高效地传递,促进碳的同化; 贵州花溪种源硝酸还原酶活性最大,硝态氮含量最高,对氮元素的利用能力较强,能够促进植物蛋白质、氨基酸和叶绿素等的合成; 贵州望谟种源根系活力最大,吸收养分的能力强。(3)各种源间苗高、地径和生物量的分配存在显著差异,浙江杭州种源的植株枝叶繁茂、根系发达,生长表现好,安徽黄山种源的植株矮小,生长表现较差; 浙江杭州种源将生物量更多分配在根和叶,提高其根系吸收养分和叶片获取光能的能力,安徽黄山种源总体生物量积累最少,长势最差。(4)通过主成分分析法对各种源的花榈木适应性进行综合评价,结果显示浙江杭州种源>贵州黎平种源>浙江永康种源>贵州望谟种源>福建建瓯种源>贵州凯里种源>贵州石阡种源>贵州花溪种源>贵州平塘种源>安徽黄山种源。综上结果表明,浙江杭州、贵州黎平和浙江永康种源花榈木对贵阳地区立地环境具有较强的适应能力和生长潜力。