Nursery Inoculation Research Articles

English

The production of quality native plants materials is essential to large- scale reclamation efforts being undertaken at mine sites throughout the United States. Some studies have shown that nursery inoculation with arbuscular mycorrhizal (AM) fungi improved survival, growth, and drought tolerance of installed tree and shrub seedlings. The production of AM-colonized plant material, however, has proven problematic due to a lack of integration between the biotechnical firms that produce inoculum and cultural procedures at commercial nurseries. The objective of our research has been to integrate mycorrhizal inoculum successfully into a nursery program, thereby, producing plant materials with improved outplanting performance. Multiple studies were conducted to investigate the efficacy of various inoculum products, the influence of growth media types, and the influence of standard fertilization techniques on the ability of AM fungi to colonize plant materials under nursery conditions. Our research has resulted in a growth media which promotes colonization of plant materials by AM inoculum in a nursery environment. Plants produced by this tecnhique have significantly higher colonization rates than controls. This study reviews the results of greenhouse trials to increase AM-colonization rates in plant materials and outplanting field trials established in Oregon, Montana, and Utah to compare traditionally grown seedlings with those grown in the AM-promoting growth media formulation.

Current status of resistance breeding of Japanese pine species to pine wilt disease

The past 30 years’ resistance breeding work for Japanese pine to pine wilt disease was reviewed from the operational aspects. The resistance breeding program initiated in 1978 in southeastern region identified 16 clones of black pines and 98 clones of red pines as tolerant as loblolly pine. A similar grogram was also started in northeastern region since 1992. More than 10 ha of seed orchards were established for both species with the selected pines and they are now in operational seed production. The progeny showed much higher in survival as compared to the unselected ones at the nursery inoculation tests; 35% higher for black pine and 18% for red pine. These progeny are further screened by the inoculation before out‐planting and it will bring about additional 20% increase in survival for black pine within the range 25 to 60% of average survival rate. A mass production system for rooted cutting from pre‐screened seedling was developed and it is expected to reduce the production cost by 40%. The progeny of the selected pines showed better in tolerance to the natural infection unless they were exposed to the excessive environmental stress without any other protection measures. Seed orchard improvement based on progeny tolerance has become a realistic option for red pine and it will bring about additional 10% increase in nursery survival. Since the results of inoculation tests with control pollinated progeny indicated that the tolerance was inherited additively, large scale control pollination and simple mass selection using open pollinated progeny are conducted concomitantly to obtain more tolerant pines together with a research to develop MAS.

Field performance of conifer and hardwood species 5 years after nursery inoculation in the Canadian Prairie Provinces

The field performance of conifer and hardwood species inoculated with different inoculation treatments was evaluated 5 or 3 years after outplanting in the field trials established in the Canadian Prairie Provinces. In conifer trials, the growth of white spruce, black spruce, lodgepole pine, and larch seedlings observed on different sites varied greatly to different inoculation treatments depending on plant and fungal species involved. Five years after outplanting, most of the introduced fungi were replaced by several indigenous ectomycorrhizal fungal species except for Laccaria bicolor strain. Survival rates of most of the inoculated seedlings were not significantly different from control seedlings naturally colonized by other resident fungi. In hardwood trial, the effects of nursery inoculation of different poplar clones, aspen and balsam poplar were very limited. Growth and survival data were combined into seedling volume and plot volume index (PVI) for measurement of total growth response of seedlings. Our results demonstrated that certain inoculated plant-fungus combinations have played a positive role during the initial establishment of these seedlings in the field, which was reflected on significantly greater stem volume and PVI compared to non-inoculated control seedlings. The results from this study provided useful information on field evaluation for potential benefits of mycorrhizal inoculation in nursery.

Inoculation of Pinus halepensis Mill. with selected ectomycorrhizal fungi improves seedling establishment 2 years after planting in a degraded gypsum soil

Vegetative inoculum of Amanita ovoidea (Bull.) Link and three isolates of Suillus collinitus (Fr.) Kuntze, as well as spore inoculum of Rhizopogon roseolus (Corda) Th. M. Fr. and S. collinitus, were evaluated for the production of Pinus halepensis Mill. in nursery and for the establishment of seedlings in a degraded gypsum soil. In nursery, most of the fungi significantly improved the height of seedlings and modified the accumulation of nutrients in needles. The percentage of ectomycorrhizas (ESR) per seedling ranged from 25 to 78%, depending on the fungi. One and 2 years after planting in the field, the survival of seedlings was significantly improved by inoculation with two isolates of S. collinitus and with spores of the same fungus. Inoculation with A. ovoidea had no significant effect on seedling survival, whilst R. roseolus caused a significant mortality of seedlings. Seedling height was significantly improved by inoculation with all fungi except R. roseolus and isolate CCMA-1 of S. collinitus. One year after planting, mycorrhization of control seedlings was negligible, and percentages of ESR were under 38% for the rest of treatments. In spring of the second year, seedlings in all treatments, including the control, became highly mycorrhizal (60-77% of ESR). Low ectomycorrhizal diversity (five morphotypes described) and seasonal variation on morphotype composition were detected 2 years after plantation. From a perspective of soil restoration management under limiting environmental conditions, nursery inoculation with selected fungi can be a key advantage for tree seedlings to surmount the initial transplant stress, assuring their establishment in the field. Our results emphasise the importance of selecting compatible fungal-host species combinations for nursery inoculation and sources of inoculum adapted to the environmental conditions of the transplantation site.

Inoculation of green alder ([Alnus crispa]) with Frankia-Ectomycorrhizal Fungal Inoculant Under Commercial Nursery Production Conditions

We examined the feasibility of producing container <i>Alnus crispa</i> (Ait.) Pursh (Betulaceae) seedlings (green alder) inoculated with a pure culture of <i>Frankia</i> sp., Brunchorst strain AvcI1 and an ectomycorrhizal fungus, <i>Hebeloma crustuliniforme</i> (Bull. ex st. Amans) Quél. in a commercial nursery setting. Alders are actinorhizal plants that fix atmospheric nitrogen in a symbiotic association with <i>Frankia</i> species and can also form mycorrhizal associations. <i>Frankia</i> inoculation significantly increased seedling biomass, number of nodule lobes, nodule weight, and plant nitrogen content of green alder at the end of nursery culture compared with control or “<i>Hebeloma</i> only” treatments. Improved seedling growth, root nodulation, and nitrogen nutrition achieved in this study was attributable to <i>Frankia</i> inoculation, suggesting <i>Frankia</i> inoculation in nursery may be beneficial for the production of superior alder seedlings to use in reclamation work. Actinorhizal plants have the potential to enhance plant establishment on disturbed sites and to improve soil fertility and stability. Seedlings inoculated with <i>Hebeloma</i> only or in combination with <i>Frankia</i> did not show any visible ectomycorrhizal colonization, suggesting <i>H. crustuliniforme</i> may not be compatible with green alder under these experimental conditions. This study demonstrated the suitability of producing large-scale inoculated alder seedlings in commercial nurseries without altering regular nursery operations.

Nursery inoculation of tomato with arbuscular mycorrhizal fungi and subsequent performance under irrigation with saline water

Protected horticultural crops as well as those planted in open fields particularly in the Mediterranean region have to cope with increasing salinization ofirrigation water. High salinity of the supply water has detrimental effects on soil fertility and plant nutrition and reduces crop growth and yield. This study was conducted to determine if pre-inoculation of transplants with arbuscular mycorrhizal (AM) fungi alleviates salt effects on growth and yield of tomato (Lycopersicon esculentum Mill. Cv. Marriha) when irrigated with saline water. Tomato seeds were sown in polystyrene trays with 20 cm 3 cells and treated with AM fungi (AM) or without (nonAM) Glomus mosseae. Once the seedlings were reached appropriate size, they were transplanted into nonsterile soil in concrete blocks (1.6 m 3m 0.75 m) under greenhouse conditions. The soil electrical conductivity (ECe) was 1.4 dS m 1 . Plants were irrigated with nonsaline water (ECw = 0.5 dS m 1 ) or saline water (ECw = 2.4 dS m 1 ) until harvest. These treatments resulted with soil EC at harvest 1.7 and 4.4 dS m 1 for nonsaline and saline water treatments, respectively. Root colonization with AM fungi at flowering was lower under saline than nonsaline conditions. Pre-inoculated tomato plants with AM fungi irrigated with both saline and nonsalinewater had greater shoot and root dry matter (DM) yield and fruitfresh yield than nonAM plants. The enhancement in fruit fresh yield due to AM fungi inoculation was 29% under nonsaline and 60% under saline water conditions. Shoot contents of P, K, Zn, Cu, and Fe were higher in AM compared with nonAM plants grown under nonsaline and saline water conditions. Shoot Na concentrations were lower in AM than nonAM plants grown under saline water conditions. Results indicate that pre-inoculation of tomato transplants with AM fungi improved yield and can help alleviate deleterious effects of salt stress on crop yield. # 2006 Elsevier B.V. All rights reserved.

Molecular markers detecting an ectomycorrhizal Suillus collinitus strain on Pinus halepensis roots suggest successful inoculation and persistence in Mediterranean nursery and plantation

Survival of the ectomycorrhizal fungal strain Suillus collinitus Sc-32 on Pinus halepensis after inoculation and outplanting was monitored in a Mediterranean plantation. Three molecular fingerprints were developed: RFLP of the internal transcribed spacer ribosomal DNA, intersimple sequence repeat, and a specific sequence-characterized amplified region marker. The inoculant was demonstrated to survive on inoculated seedlings 4 years after outplanting (56 months after inoculation), although S. collinitus was not fruiting. The designed markers set allows reliable and inexpensive monitoring of inoculated seedlings and suggests that S. collinitus is suitable for inoculation of Mediterranean Pinus. These data are discussed in the framework of suilloid population ecology.

Nursery inoculation of Eucalyptus seedlings in Western Australia and Southern China using spores and mycelial inoculum of diverse ectomycorrhizal fungi from different climatic regions

A large-scale ectomycorrhizal (ECM) fungus inoculation program was conducted in plantation forest tree nurseries in Australia and China over a period of 2 years. These experiments used a wide diversity of fungi (90 isolates belonging to 23 genera), most of which were obtained from Australian eucalyptus plantations or forests. These trials compared the effectiveness of mycelial slurries (homogenised liquid fungal cultures) and spore suspensions (ground dried fruit bodies) as inoculum forms in nurseries with widely differing management regimes. The success rate of inoculation was moderate, regardless of nursery management regime (38% overall). However, there were substantial differences in overall performance between fungal genera, with agaricoid genera, such as Descolea and Laccaria, and hypogeous (truffle-like) fungi performing better than sequestrate genera, such as Pisolithus and Scleroderma. Comparison of congeneric fungal isolates from different climatic regions did not show significant differences in the performance of fungi from regions where climatic conditions were most similar to nursery conditions relative to those from disparate climatic regions (tropical, temperate, or mediterranean). There was a higher overall success rate for inoculation with spore suspensions (49%) than for mycelial slurries obtained from liquid cultures (35%). Spore-based inoculum was also easier to use and much less expensive to produce than mycelial slurries. It is recommended that future studies investigate the use of mixtures of fungi and attempt to optimise spore germination to increase the reliability of eucalypt seedling nursery inoculation.

Genetic Analysis of Growth and Susceptibility to Bacterial Wilt (Ralstonia solanacearum) in Eucalyptus by Interspecific Factorial Crossing

Summary Factorial mating crosses of Eucalyptus urophylla × E. tereticornis (3 x 5), E. urophylla × E. camaldulensis (3 x 3) and E. urophylla × E. exserta (3 x 3) were used for genetic analysis of growth traits and susceptibility to bacterial wilt (Ralstonia solanacearum). Genetic effects including female, male and female × male interaction were examined for height (H) and diameter at breast height (DBH) at age five as well as final bacterial wilt index (BWI) in both nursery inoculation and field assessment by five years of age. Female, male and female x male variances appeared to have a significant role in growth traits H and DBH though their magnitude varied for the factorials studied. For the trait BWI additive (male) and dominant (female x male) effects were both involved in the genetics of bacterial wilt susceptibility, and additive was the major. Estimates of narrow-sense heritability (h2) for H, DBH and BWI ranged from 0.11 ± 0.06 to 0.70 ± 0.09, varying with either trait or factorial. Growth traits (H and DBH) had low and non-significant phenotypic and genetic correlations with BWI in all the three factorials, ranging from -0.10 ± 0.08 to 0.17 ± 0.14 in coefficient of correlation. This indicates that it may be possible to select superior trees with both fast growth and high resistance to bacterial wilt in eucalypt hybrid populations in operational breeding programs.

Effectiveness of mycorrhizal inoculation in the nursery on growth and water relations of Pinus radiata in different water regimes.

We compared the performance of mycorrhiza-inoculated and non-inoculated radiata pine (Pinus radiata D. Don) seedlings in two field studies. In the first study, above ground growth of 2-year-old container-grown trees was compared after planting in two areas that differed in water availability. Mycorrhizal inoculation significantly improved above ground growth in the 2 years after planting in both areas, especially at the drier site. In the second study, the influence of Rhizopogon roseolus (Corda ex Sturm) Th. Fries and Scleroderma citrinum Pers. on xylem water potential and hydraulic conductance at the soil-root interface of trees established at the same sites was assessed. Nursery inoculations with R. roseolus and S. citrinum improved tree growth during the first 2 years after field outplanting, particularly at the drier site.

Survival of ponderosa pine (Pinus ponderosa Dougl. ex LAWS.) seedlings Outplanted with Rhizopogon mycorrhizae inoculated with spores at the Nursery

Numerous studies have shown that ectomycor-rhizal fungi can profoundly affect conifer performance by facilitating nutrient and water uptake, maintaining soil structure, and protecting roots from pathogens and environmental extremes. However, fertilizing and irrigating practices in seedling production nurseries are very different than field conditions at harsh outplanting sites. More information is needed on the ability of specific mycorrhizal fungi to establish at the nursery and improve seedling performance in the outplanted environment. This study was conducted to test the ability of a specific ectomycorrhizal fungus, Rhizopogon rubescens, inoculated onto the root systems of plug-1 ponderosa pine (Pinus ponderosa) seedlings grown in fumigated and nonfumigated bare-root nursery beds to influence conifer establishment on two harsh, dry sites in southwest Oregon, U.S. After outplanting, survival of Rhizopogon-inoculated seedlings were significantly higher than noninoculated seedlings at both field sites (p &lt; 0.05). Survival averaged 93% for Rhizopogon-inoculated seedlings and 37% for noninoculated seedlings at the Central Point site. Survival averaged 71% for Rhizopogon-inoculated seedlings and 41% for noninoculated seedlings at the Applegate site. Field survival did not differ significantly for ponderosa pine seedlings grown in fumigated compared to nonfumigated beds. Seedling height did not differ significantly between Rhizopogon-inoculated and noninoculated ponderosa pine seedlings or fumigated and nonfumigated beds in the nursery or outplanting sites. Foliar analysis at the Applegate site indicated significantly higher phosphorous contents for Rhizopogon-inoculated seedlings. Results from this study indicate that Rhizopogon inoculated plug-1 ponderosa pine survive at a much higher rate on dry, harsh sites in southwest Oregon. Poor survival by noninoculated pine seedlings grown in both fumigated and nonfumigated beds and outplanted on harsh sites indicate that field survival should be considered one of the more important criteria for selection of Rhizopogon species suitable for nursery inoculation.

Microsite and mycorrhizal inoculum effects on the establishment of Quercus coccifera in a semi-arid degraded steppe

Alpha grass ( Stipa tenacissima) steppes are widely distributed within the semi-arid areas of the Mediterranean Basin, and represent a degraded stage of vegetation. We evaluated the effect of S. tenacissima tussocks and nursery inoculation with mycorrhizae on the survival of the native shrub Quercus coccifera. Experiments were carried out in three steppes located in semi-arid southeastern Spain. Survival during the first months after plantation was significantly higher in the surroundings of S. tenacissima tussocks than in open areas between the tussocks. We did not find any effect of nursery inoculation on seedling survival. This effect may be related to the fact that the used fungal strain did not survive the drought summer conditions in the study area. Our results support the idea of a facilitative effect of S. tenacissima on introduced shrubs, which may be related to improved environmental conditions in tussock microsites. However, this effect may not be enough for the establishment of seedlings in years with below-average rainfall and a strong summer drought.

Effects of P fertilisation and ectomycorrhizal fungal inoculation on early growth of eucalypt plantations in southern China

Eucalypt plantations in China have largely been established on soils that are low in phosphorus (P) and have few eucalypt-compatible ectomycorrhizal fungi. Effects of P application and ectomycorrhizal fungal inoculation on early tree growth in plantations of Eucalyptus urophylla Blake in Guangdong (Gaoyao) and E. globulus Labill. in Yunnan (Chuxiong) in southern China were investigated as part of a larger study. Application of superphosphate at establishment, in the presence of a basal fertiliser, increased early growth of E. urophylla and E. globulus. The optimum treatments for maximum stand volume at year 3 were 200 kg P ha−1 which increased stand volume by 750% on the strongly acidic, P-deficient lateritic red oxisol at Gaoyao, and 40 kg P ha−1 which increased stand volume by 55% on the mildly P-deficient red ultisol at Chuxiong, at 3 years. Superphosphate increased tree survival at Gaoyao as well as at Chuxiong. Nursery inoculation of eucalypt seedlings with ectomycorrhizal fungi significantly affected tree height and stand volume of the E. urophylla plantation, but the effect (positive or negative) was isolate-dependent and related to tree survival rate. A Laccaria isolate (CSIRO E4728) significantly increased stand volume by 27% at Gaoyao and a Scleroderma (MURU LH041) increased growth by 15% at Chuxiong at age 3 years. All isolates increased tree growth under P-limited soil conditions and only one isolate increased tree growth at marginal soil P. The results suggest that tree growth should be able to be optimised in plantations by the use of effective ectomycorrhizal fungi combined with a judicious fertilisation program at establishment.

Effects of reafforestation techniques on the nutrient content, photosynthetic rate and stomatal conductance ofPinus Halepensis seedlings under semiarid conditions

A field experiment was carried out to evaluate the effect of different soil preparation techniques for Pinus halepensis afforestation on physiological parameters in Mediterranean summer conditions. The soil preparation treatments consisted of terracing (mechanical and manual) and the addition of an organic amendment (urban solid refuse). The mycorrhizal treatments consisted of nursery inoculation with Pisolithus arhizus and the addition of forest soil to the planting holes. Six years after planting the study revealed significant differences in heights and basal diameters, phosphorus and potassium concentrations in the leaves and photosynthetic rate and stomatal conductance. The pines grown in the manually prepared terraces were subjected to strong water stress, as reflected by the high A:gs ratios and highest levels of phosphorus and potassium in leaves. Mechanical terracing and the addition of urban solid refuse produced a higher photosynthetic rate, and a combination of these treatments was particularly effective. Copyright © 2000 John Wiley & Sons, Ltd.

Field performance in northern Spain of Douglas-fir seedlings Inoculated with ectomycorrhizal fungi

Experimental plantations were established in northern Spain to determine the effects of different ectomycorrhizal fungi on growth and survival of Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) under field conditions. Douglas-fir seedlings were inoculated with Laccaria bicolor S238 mycelia in two bareroot nurseries in central France or with spore suspensions of three hypogeous ectomycorrhizal species: Melanogaster ambiguus, Rhizopogon colossus and R. subareolatus, in a Spanish containerised nursery. The effects of ectomycorrhizal inoculation on plant survival after outplanting were limited, being only significant at the Guipuzkoan (Spain) site, when plants inoculated with L. bicolor S238 were compared to non-inoculated plants grown in non-fumigated soil. L. bicolor S238 had a significant effect on plant growth during the phase of bareroot nursery growth and this difference was maintained after field outplanting. Nursery inoculations with M. ambiguus, R. colossus and R. subareolatus improved plant growth during the first 2 and 3 years after field outplanting. The positive effects of the inoculation treatment on seedling height, root collar diameter and stem volume persisted after 5 years of field growth. Inoculation with these ectomycorrhizal fungi may improve the field performance of Douglas-fir seedlings in northern Spain.

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.

Glomus -wetland rice mycorrhizas influenced by nursery inoculation techniques under high fertility soil conditions

We investigated the effect of nursery inoculation techniques on mycorrhizal colonization and sporulation, growth responses, and nutrient (N and P) uptake to determine the suitable nursey inoculation method of wetland rice (Oryza sativa L.) under high-fertility soil conditions. Seedlings were produced in dry-nursery (DN, watered to 60% of –0.03 MPa) and wet-nursery (WN, 3–5 cm water from the soil surface) conditions with or without arbuscular mycorrhizal fungal (Glomus spp.) inoculation. Soil was γ-ray sterilized before use in this experiment. Mycorrhizal fungal colonization was 56% in DN and 23% in WN plants at 6 weeks of growth. The arbuscular mycorrhizal fungal colonization was significantly higher in plants of DN origin than in WN plants after transplantation to the pots, irrespective of growing stages. Mycorrhizal colonization was significantly decreased to 28% in DN plants and to 25% in WN plants at harvest. The grain yield was significantly influenced by nursery conditions. N and P acquisition of wetland rice plants inoculated with Glomus spp. was significantly greater than that of non-inoculated plants at maturity, especially in those originating from DN conditions. P translocation from shoots to grain was accelerated by mycorrhizas.

The Role of Mycorrhizae, Site Preparation, and Organic Amendment in the Afforestation of a Semi-Arid Mediterranean Site with Pinus halepensis

Abstract A factorial field experiment was conducted in a degraded semi-arid site of southeastern Spain to test the effectiveness of mycorrhization and several soil preparation techniques on afforestation with Pinus halepensis. The mycorrhizal treatments were nursery inoculation with Pisolithus arhizus and forest soil addition to the planting holes. The soil preparation treatments were terracing(mechanical and manual) and the addition of an organic amendment (urban solid refuse). One year after planting, the study revealed significant differences in mycorrhization levels, frequency of mycorrhizal species, fine root production and growth between the inoculated seedlings and the noninoculated controls. Inoculation with P. arhizus gave better pine growth and mycorrhization rates than the addition of forest soil. Both mycorrhization treatments were particularly effective in combination with mechanical terracing. The organic amendment had no apparent negative influence on the mycorrhization level of the seedlings and significantly improved pine growth. The beneficial effects of mycorrhization treatments on P. halepensis growth persisted 2 yr after planting. The increase in growth of the seedlings due to the treatments could be attributed to the change in soil conditions (increased fertility and soil aeration) and probably to a mycorrhization effect on water relations, although it has not been clearly demonstrated. FOR. Sci. 43(2):203-211.

Screening of Mycorrhizal Arbuscular Fungi for Nursery Production of Banana Vitroplants

In western Mexico, banana is traditionally multiplied by vegetative reproduction in the orchard; recently, micropropagation of this species has increased considerably. Banana has been shown to give a positive response to AM fungal inoculation. However, the selection of efficient AM fungi species, currently propagated in vitro, has not been documented. The selection of the most-effective arbuscular mycorrhizal (AM) fungi for growth enhancement of banana vitroplants is the first step toward development of an AM inoculation system. This work reports the effect of nursery inoculation of Glomus aggregatum, G. clarum, G. etunicatum, G. intraradices, G. monosporum, G. mosseae, and Gigaspora margarita on the banana vitroplants growth. Pots (4 kg) containing a mixture of soil and coconut fiber (1:1) sterilized with methyl bromide were used. Treatments were arranged under a fully randomized experimental design with eight replications. The plants were harvested 120 days after inoculation and plant height, number of leaves, leaf area, fresh weight of roots, mycorrhizal colonization, and intensity of infection were measured. Glomus etunicatum, G. monosporum, G. mosseae, and G. aggregatum were shown to be the most-effective endophytes. Plant height was increased, as well as the production of banana roots in response to mycorrhizal inoculation with these fungi. On the other hand, G. intraradices and G. clarum showed low levels of colonization. The data clearly show the most efficient AM fungi for future inoculation studies in nursery banana production.

Response of 11 eucalyptus species to inoculation with three arbuscular mycorrhizal fungi

Numerous publications have reported growth stimulation of Eucalyptus following ectomycorrhizal inoculation in nursery or field conditions. Although Eucalyptus species can also form arbuscular mycorrhiza, their dependency on this type of mycorrhiza is still debatable. This paper presents information on the effect of inoculation of arbuscular mycorrhizal fungi on eucalypt growth. Twenty weeks after mycorrhizal inoculation, Eucalyptus seedlings' stem dry weight could be increased up to 49% compared to non-inoculated control plants. Intensity of root colonization by a given fungus depended on the host species, but it was not related to a plant growth response. Leaf phosphorus concentration of non-inoculated Eucalyptus seedlings varied greatly between species. Increases in leaf phosphorus concentration following mycorrhizal infection were not necessarily associated with plant growth stimulation. The most mycorrhiza-dependent Eucalyptus species tended to be those having the highest leaf phosphorus concentration in the absence of a fungal symbiont. These mycorrhiza-dependent Eucalyptus species seem to have greater phosphorus requirements and consequently to rely more on the symbiotic association.