Influence of the fertilisation method in controlled ectomycorrhizal inoculation of two Mediterranean pines

The influence of the fertilisation method: soluble (SF) vs. slow-release fertiliser (SRF) and of inoculation with Laccaria laccata (Scop.) Fr., Pisolithus tinctorius (Pers.) Coker & Couch and Melanogaster ambiguus (Vittad.) Tul & C. Tul. on ectomycorrhizal colonization and growth of Pinus pinea L. and Pinus pinaster Ait. was evaluated. For both pines, mycorrhization with L. laccata was not affected by the fertilisation method. Percentages of ectomycorrhizas (ECM) formed by P. tinctorius were dependent on the fertilisation method, the inoculum type (vegetative or spores) and the pine species involved. ECM formed by M. ambiguus were increased with fertilisation in both pines. Inoculation significantly improved P. pinea biomass when seedlings were fertilised with SRF whereas no effect was found in non-fertilised ones. For non-fertilised P. pinaster, inoculation with L. laccata and both inocula of P. tinctorius increased seedling biomass whereas fertilisation neutralised the fungal effect. Fertilisation increased P. pinea and P. pinaster biomass, independently of the inoculation treatment.     

施肥方式及接种菌根真菌对1年生油松苗木质量的影响

为评价施肥方式和接种菌根真菌处理对油松苗木质量的影响,在大田条件下,以1年生油松接菌苗(简称+M)和非接菌苗(简称-M)为研究材料,设置3种施肥处理(常规施肥(CF)、指数施肥(EF)、2倍指数施肥(DEF))试验,对比分析不同处理对苗木形态和综合质量指标的影响.研究结果表明:1)EF处理下,+M和-M处理间油松苗木菌根侵染率无显著差异;而CF和DEF处理下,+M处理油松苗木菌根侵染率较-M处理显著增加了35.7％(P<0.05)和35.0％(P<0.05).2)3种施肥处理下,苗高和地径均为+M高于-M处理,且在+M和EF组合处理下苗木的苗高和地径均达到最大;而+M和CF组合处理下苗木主根长最小,侧根数最大.3)在+M和EF组合处理下油松苗木总生物量和地下生物量均最大,且地下生物量占总生物量的比例最高.4)与-M处理和CF、EF、DEF组合处理相比,+M与EF组合处理下苗木质量指数分别增加了23.8％(P<0.05)、21.0％(P<0.05)、27.7％(P<0.05).综上所述,指数施肥结合接种菌根真菌处理有利于促进油松苗木生长.     

Production of cuttings in response to stock plant temperature in the subtropical eucalypts, Corymbia citriodora and Eucalyptus dunnii

Propagation of subtropical eucalypts is often limited by low production of rooted cuttings in winter. This study tested whether changing the temperature of Corymbia citriodora and Eucalyptus dunnii stock plants from 28/23°C (day/night) to 18/13°C, 23/18°C or 33/28°C affected the production of cuttings by stock plants, the concentrations of Ca and other nutrients in cuttings, and the subsequent percentages of cuttings that formed roots. Optimal temperatures for shoot production were 33/28°C and 28/23°C, with lower temperatures reducing the number of harvested cuttings. Stock plant temperature regulated production of rooted cuttings, firstly by controlling shoot production and, secondly, by affecting the ensuing rooting percentage. Shoot production was the primary factor regulating rooted cutting production by C. citriodora, but both shoot production and root production were key determinants of rooted cutting production in E. dunnii. Effects of lower stock plant temperatures on rooting were not the result of reduced Ca concentration, but consistent relationships were found between adventitious root formation and B concentration. Average rooting percentages were low (1–15% for C. citriodora and 2–22% for E. dunnii) but rooted cutting production per stock plant (e.g. 25 for C. citriodora and 52 for E. dunnii over 14 weeks at 33/28°C) was sufficient to establish clonal field tests for plantation forestry.     

Augmented growth of long pepper in response to arbuscular mycorrhizal inoculation

Arbuscular mycorrhizal (AM) technology is a soil-based fertilization practice for sustainable crop productivity. We evaluated six indigenous Arbuscular mycorrhizal fungi (AMF) strains for their symbiotic response with Piper longum (long pepper), a non-timber forest product holding promise as a commercial crop for its medicinal fruits and roots. Piper saplings were raised in a 10 cm thick sand and soil mix inoculated with various AMF. Under field conditions, plants inoculated with AMF demonstrated better survival (≥80%) than non mycorrhizal plants (58%). Almost all the studied AMF strains increased the plant growth, biomass and nutrient content (N and P) over the uninoculated control. Mycorrhizal inoculation with four AMF species, viz: Glomus fasciculatum, G. clarum, G. etunicatum and G. versiforme greatly enhanced long pepper growth both in the nursery and field conditions.     

Influence of ectomycorrhizal fungal inoculation on growth and root IAA concentrations of transplanted conifers

We determined whether in vitro plant growth regulator production by mycorrhizal fungi is correlated with conifer seedling growth and root IAA concentrations. Container-grown seedlings of interior Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco), lodgepole pine (Pinus contorta Dougl.) and ponderosa pine (Pinus ponderosa Dougl.) were inoculated at seeding with ectomycorrhizal fungi having a high, moderate or low capacity to produce either IAA or ethylene in vitro. Inoculated seedlings were grown for one season in the nursery, harvested in December, cold stored over winter and then transplanted to either a nursery field or a forest site in the spring. Seedling morphology and endogenous IAA in roots were measured immediately after cold storage and again six and 12 months after transplanting. Morphological responses to inoculation varied among different mycorrhizal fungi. Free IAA concentration of roots was increased in some inoculation treatments for all conifer species. In seedlings transplanted to a nursery field, in vitro ethylene-producing capacity of the ectomycorrhizal fungi was highly correlated with more morphological features than in vitro IAA-producing capacity. Both IAA- and ethylene-producing capacity were significantly correlated with more morphological features in seedlings transplanted to a forest site than in seedings transplanted to a nursery field. One year after transplanting, only in vitro IAA-producing capacity was correlated with endogenous IAA concentration of roots of the inoculated seedlings. We conclude that growth responses of conifer seedlings can be partially influenced by IAA and ethylene produced by ectomycorrhizal fungal symbionts.     

Improved parameters of Pinus greggii seedling growth and health after inoculation with ectomycorrhizal fungi

Pinus greggii Engelm. ex Parl. is an endemic pine of Mexico with notorious adaptability to eroded, shallow and poor soils. It is widely used in reforestation programmes worldwide. The purpose of the present study is to develop an ectomycorrhizal fungi (ECM) treatment with different native ectomycorrhizal fungal species (collected in P. greggii and Abies vejarii stands) to improve seedling survival of P. greggii. Four-month-old P. greggii var. greggii seedlings were inoculated with ground fruiting bodies of the ECM species Astraeus spp., Boletus barrowsii, Geastrum minimum, Lactarius deliciosus var. deterrimus, Russula cf. atroglauca, Russula spp., Suillus caerulescens, as well as a mixture of three species (Russula sp., R. lutea and L. deliciosus) and soil litter with mycelium from the base of a fruiting body of L. deliciosus. Agronomic variables, and total phosphorous and glucosamine contents were measured in P. greggii seedlings. Inoculated treatments with B. barrowsii, Geastrum minimum and S. caerulescens showed increases in seedling height and basal diameter as well as dry shoot biomass compared with those of the control plants. Geastrum minimum, B. barrowsii and R. xerampelina significantly increased values of dry weight compared with that of the control. Inoculation of soil litter from the base of a fruiting body of L. deliciosus induced the maximum glucosamine response (40.2 mg g^?1 of dry root biomass). Geastrum minimum, a fungus collected in P. greggii stands, enhanced basal diameter of pine seedlings in the nursery. Fungal species B. barrowsii, Suillus caerulescens, Russula cf. atroglauca and Russula spp. from the Abies forest improved plant quality in terms of the Dickson quality index and root and shoot biomass, compared with those of the control.     

Agrobacterium rhizogenes-mediated transformation to improve rooting ability of eucalypts

In an attempt to improve rooting in in vitro propagated Eucalyptus clones, root-inducing genes on the Ri plasmids of three Agrobacterium rhizogenes strains were inserted into the Eucalyptus genome. Root development was monitored in vitro and after the plantlets had hardened off. Only transformed roots grew as root cultures in hormone-free liquid medium. The potential use of this procedure for improving rooting of clonal material is discussed.     

The response of ectomycorrhizal fungi on Pinus densiflora seedling roots to liquid culture

Japanese red pine (Pinus densiflora) seedlings taken from a nursery were grown in liquid culture with all roots entirely submerged in water. The aims of the present study were to observe the reactions of preformed ectomycorrhizae to liquid culture and to examine new infections by ectomycorrhizal fungi on newly formed root tips in liquid culture. Inoculation levels were controlled by trimming the ectomycorrhizal roots to one of three selected root lengths. The results showed that the mantles of pre-formed ectomycorrhizae were lost during the 8 weeks of the liquid culture and that these preformed root tips became blackish and wrinkled, but Hartig nets remained in these blackish root tips. On the newly formed lateral root tips, no ectomycorrhizal mantles were formed, although Hartig nets were found. In addition, the level of inoculum did not affect the frequency of Hartig nets in newly formed root tips, suggesting that the density of inoculum was more important than the amount of inoculum for new infection. In conclusion, ectomycorrhizal fungi endured and infected new roots while submerged; however, only Hartig nets were formed and not mantles.     

Differential phytotoxic response of cut shoots of eucalypts to culture filtrates of pink disease fungus,Corticium salmonicolor

Relative susceptibility of 23 Eucalyptus provenances of 11 species to pink disease caused by Corticium salmonicolor was assessed in culture filtrates of two isolates (CS1 from E. tereticornis and CS2 from E. grandis) of the pathogen, employing cut-shoot bioassay. The results showed statistically significant variation in response among different provenances within a species. Cut shoots of eucalypus giving susceptible response were affected significantly by the culture of filtrates at low dilutions, whereas those giving resistant response tolerated high concentration with little damage to shoots. This evidence clearly indicated an interaction between the host and culture filtrates of the pathogen. The response of CS1 and CS2 culture filtrates gave statistically significant differences in their reactions on various eucalypts, possibly indicating that the isolates are of two different strains. The criticism of cut-shoot bioassay and its significance in laboratory screening of eucalypts to pink disease are discussed.     

Effect of environment on the response of Eucalyptus clones to inoculation with Cryphonectria cubensis

The ascomycete Cryphonectria cubensis causes severe losses in Eucalyptus plantations in South Africa and selection programmes for disease tolerance are necessary. The aim of this study was to use two C. cubensis inoculation trials, planted at different locations to assess the disease susceptibility of the clones and the effect of the environment on disease development. These two trials consisted each of 21 Eucalyptus clones (E. grandis, E. grandis × camaldulensis and E. grandis × urophylla). All trees were inoculated with a single virulent strain of C. cubensis and lesion widths measured 6 and 12 months after inoculation. Clones differed significantly in their tolerance to C. cubensis. Further, disease severity differed depending on the geographical location of the trial. A significant clone × locality (genotype × environment) interaction was observed. Therefore, screening for disease resistance should take place only in areas where clones will be commercially grown.     

Soil factors influencing the growth response of <Emphasis Type="Italic">Acacia holosericea</Emphasis> A. Cunn. ex G. Don to ectomycorrhizal inoculation

Australian acacias like Acacia holosericea are excellent candidates for the revegetation of arid zones in Africa. Their high ability to develop multiple symbioses with soil microorganisms is crucial to their rapid development in adverse climatic and edaphic conditions. These symbioses include nitrogen fixation with rhizobia, vesicular arbuscular mycorrhization and ectomycorrhization. We set up an experiment to test the growth response of A. holosericea to ectomycorrhizal inoculation in 13 different soils from Senegal. After autoclaving the soil, the experiment was conducted in a greenhouse for four weeks. Plants were inoculated with Pisolithus albus strain IR100. The following parameters were measured: plant biomass, N, P, K and Ca foliar composition, spontaneous nodulation rate, and ectomycorrhizal colonization. Data were analyzed in light of the physical, chemical and total microbial characteristics of the soil. The results demonstrated a global promoting effect of P. albus inoculation on plant (shoot and root) growth and on foliar P and K, together with a depressive effect on N, while Ca rates were barely affected. Interestingly, spontaneous nodulation with putative water- or airborne rhizobia was stimulated after P. albus inoculation. However, these nodules seemed poorly effective, as they failed to cause any change in plant growth or in foliar N composition within the nodulated and nonnodulated control plants. These results show that plant growth response to ectomycorrhizal inoculation is greatly dependent on soil characteristics, and that root ectomycorrhizal colonization is influenced by biotic factors such as soil microbiota. From a practical point of view, data from the present study demonstrate that it is possible to optimize the effect of fungi on plant growth by screening soils under nursery conditions.     

Characterization of the induced response of slash pine to inoculation with bark beetle vectored fungi

Six 25- to 30-year-old slash pine, Pinus elliottii Englm. var. elliottii, trees were inoculated with Ophiostoma minus (Hedgc.) H.P. Sydow, O. ips (Rumb.) Nannf or sterile water. Two, 4 and 6 weeks after inoculation, the lengths of developing lesions and the monoterpene concentration of the necrotic tissue within each lesion were measured. Both sterile and fungal wounding resulted in the development of lesions in the phloem-outer xylem. At both 4 and 6 weeks after inoculation, lesions induced by O. minus were significantly larger than lesions induced by O. ips or sterile water, whereas the lesions induced by O. ips and sterile water were similar in size at all sampling periods. At 2, 4 and 6 weeks after inoculation, lesions induced by O. minus had significantly greater concentrations of monoterpenes than lesions induced by O. ips or sterile water. The monoterpene concentration of lesions induced by O. ips was significantly greater than that of lesions induced by sterile water only at the 6-week sampling period. Visual examination of the lesions indicated that O. minus but not O. ips was inhibiting the development of callus tissue, suggesting that the strain of O. ips was either nonpathogenic or avirulent.     

Growth stimulation of young oak plantations inoculated with the ectomycorrhizal fungus Paxillus involutus with special reference to summer drought

Nursery-grown Quercus petraea and Q. robur seedlings were inoculated with the ectomycorrhizal fungi Paxillus involutus, Hebeloma crustuliniforme or Laccaria laccata. At the end of the first growing season, the seedlings with roots colonized with the inoculated fungi were outplanted at two sites in northeastern France in 1985 or 1988. P. involutus was found to be the most competitive and efficient of the three fungi tested; its mycorrhizas were present 7 yrs after outplanting and it markedly improved the growth of both oak species. In the case of Q. robur, the growth stimulation was more marked on years with a dry summer. These results are discussed in terms of water relations and of competitiveness of the introduced versus resident symbiotic fungi.     

Diseases of eucalypts in the central and northern provinces of Mozambique

In the mid-1970s, Mozambique embarked on several forestry projects to promote and establish large plantation areas with eucalypt trees. The planted species included Corymbia citriodora, Eucalyptus camaldulensis, E. saligna and E. tereticornis. Similar to other regions of the world, pests and pathogens pose a significant threat to eucalypt plantations in Mozambique, but little is known regarding the diseases of trees in the country. The aim of this study was to provide the first detailed consideration of the possible disease problems affecting plantation- grown eucalypt species in the central and northern provinces of Mozambique. Isolates of fungal pathogens were obtained from material displaying disease symptoms collected during two field surveys conducted in 2010 and 2011. Representative fungal isolates were identified using DNA sequence data. Stem canker diseases caused by fungi in the Botryosphaeriaceae, Cryphonectriaceae and Teratosphaeriaceae, as well as leaf spots caused by species of Calonectria, Pilidiella, Pilidium and Phakopsora myrtacearum were commonly encountered. Their relative importance to the future of planation forestry in Mozambique is discussed.     

Histological analyses of the host response of two aspen genotypes to wounding and inoculation with Hypoxylon mammatum

Ramets derived from root sprouts of two quaking aspen (Populus tremuloides) parents were either mechanically wounded or wounded and inoculated with mycelium of Hypoxylon mammatum. Female aspen parents were considered either resistant or susceptible based on a 30-year field trial of their open-pollinated progenies that had 21% and 93% mortality, respectively, caused by H. mammatum. Each stem was wounded twice at the base and in the nonlignified zone. Samples were taken 5 mm above the site of wounding at 7 and 14 days. Histochemicals used were phloroglucinol-HCl and Sudan Black B to detect lignin and suberin, respectively. Thin sections of the resistant aspen ramets showed intensive staining phloroglucinol-HCl, which was localized along both sides of the wound margin. Collenchyma callus was well developed by day 7 and was derived from the phloem tissue internal to the cell walls staining positive for phloroglucinol-HCl, near the vascular cambium. In contrast, the tissues of susceptible aspen ramets were less stained, the stained cells were less scattered and less collenchyma callus had formed than on the resistant ramets. The presence of the fungus increased the amount of staining observed with phloroglucinol-HCl and delayed wound closure in both aspen genotypes. No distinguishing pattern could be identified between the two aspen genotypes with respect to suberin formation. When comparing stem response to phloroglucinol-HCl with respect to the tissue type on the same stem (succulent versus woody), the inoculation of older woody tissue resulted in a more defined host response and thus were better in separating the two aspen genotypes.     

Growth and carbon sequestration by ectomycorrhizal fungi in intensively fertilized Norway spruce forests

A substantial portion of the carbon (C) fixed by the trees is allocated belowground to ectomycorrhizal (EM) symbionts, but this fraction usually declines after fertilization. The aim of the present study was to estimate the effect of optimal fertilization (including all the necessary nutrients) on the growth of EM fungi in young Norway spruce forests over a three year period. In addition, the amount of carbon sequestered by EM mycelia was estimated using a method based on the difference in δ¹³C between C₃ and C₄ plants. Sand-filled ingrowth mesh bags were used to estimate EM growth, and similar bags amended with compost made from maize leaves (a C₄ plant) were used to estimate C sequestration. Fertilizers had been applied either every year or every second year since 2002 and the estimates of EM growth started in 2007. The application of fertilizer reduced EM growth to between 0% and 40% of the growth in the control plots at one site (Ebbegärde), while no significant effect was found at the other three sites studied. The effect of the fertilizer was similar in sand-filled and maize-compost-amended mesh bags, but the total production of EM fungi was 3-4 times higher in maize-compost-amended mesh bags. The fertilizer tended to reduce EM growth more when applied every year than when applied every second year. The amount of C sequestered in maize-compost-amended mesh bags collected from unfertilized treatments was estimated to be between 0.2 and 0.7 mg C g sand⁻¹ at Ebbegärde and between 0.2 and 0.5 mg C g sand⁻¹ at Grängshammar. This corresponds to between 300 and 1100 kg C per ha, assuming a similar production in the soil as in the mesh bags. Fertilization at the Ebbegärde site reduced carbon sequestration, which confirmed the results based on estimates of fungal growth (ergosterol levels). A correlation was found between fungal biomass and δ¹³C in mesh bags amended with maize compost. Based on this, it was estimated that a fungal production of 1 μg ergosterol corresponded to 0.33 mg of sequestered carbon. In conclusion, the effect of the fertilizer on EM growth seemed to be dependent on the effect of the fertilizer on tree growth. Thus, at Ebbegärde, were tree growth was less stimulated by the fertilizer, EM growth was reduced upon fertilization. At other sites, where tree growth was more stimulated, the fertilizer did not influence EM growth. The large amounts of carbon sequestered during the experiment may be a result of fungal residues remaining in the soil after the death of the hyphae.     

矮生沿阶草栽培基质配方筛选试验

为加速矮生沿阶草繁殖和推广,通过5个不同的基质配方,研究了不同基质配方施用对矮生沿阶草生长的影响。综合叶片生长速率、出叶速率、分蘖数、叶绿素含量、单位时间内新根鲜质量、根系活力等测定结果认为,基质配方按泥炭∶砻糠∶黄土为2∶2∶1的比例进行配制最有利于矮生沿阶草的生长。     

Growth response of black walnut to interplanted trees

Analyses of black walnut tree diameters 13 years after planting showed that interplanting autumn-olive, black locust, and European alder increased walnut tree growth, but only at certain locations. Interplanting autumn-olive resulted in increases of 56 to 351% at four of five locations and all species resulted in doubled walnut growth on an upland site. The interaction between treatment and location indicates that a fuller understanding of site and nurse species characteristics is needed to obtain the potential benefits of mixed plantings.     

Wound response of Eucalyptus clones after inoculation with Cryphonectria cubensis

Twenty-five different Eucalyptus grandis clones were artificially wounded and inoculated with a virulent isolate of Cryphonectria cubensis. The capacity of wounds to close through callus production was correlated with the relative susceptibility of these clones to infection by C. cubensis. Clones with the greatest capacity to close wounds were those that were also most tolerant to C. cubensis infection. Those with a lower capacity to close wounds were most susceptible to Cryphonectria canker.