Non-inoculated Control Seedlings Research Articles

Quality Stock Production of Aquilaria malaccensis Lamk. Using Arbuscular Mycorrhizal Inoculation: Restoration of Agarwood Source

Aquilaria malaccensis Lamk. is a critically endangered and economically important forest tree species of North-east India. In the current study, a biotization experiment was performed to show the effect of arbuscular mycorrhizae on obtaining high-quality agarwood-producing plants. One-month-old seedlings were inoculated in a designed experiment with single and combined endomycorrhizal treatments. All inoculated seedlings showed significant biomass production than control seedlings. The Biovolume index (Bi) was higher in all inoculated plant seedlings than in non-inoculated control seedlings but Acaulospora spp. (EM2) treatment had a higher Bi (78.17±0.024) than the rest of the inoculation treatments. The Quality index (Qi) value was also high (1.22±0.024) in EM2 treatment followed by the Glomus spp. + Acaulospora spp. (EM1+EM2) treatment (1.10±0.031) and Glomus spp. (EM1) (0.83±0.014) treatment. Control seedlings had a lower value (0.14±0.021) of Qi than the rest of the treatments. The plastochrone interval index (Pi) of A. malaccensis after 60 days of inoculation was low in EM1+EM2 treatment as the time interval for initiation of 2nd leaf was 1 day than rest of the treatments in which the time interval was 4 days for initiation of the 2nd leaf primordia. Substantially, the leaf primordia appearance in the EM1+EM2 treatment was impetuous than rest of the treatments. In the control treatment, the 8th leaf primordia appeared on the 36th day and after that, there was no appearance of leaf primordia. Therefore, the EM2 treatment was the best single/alone treatment of mycorrhizal inoculation followed by EM1+EM2 synergistic treatment for quality stock production of A. malaccensis seedlings.

Root discoloration and shoot symptoms in silver birch after Phytophthora infection in vitro.

There are no records of established plant pathogenic Phytophthora species in Finnish forests, but they are likely in the future. Therefore, the effects of Phytophthora inoculations on young, ca. 2-month-old silver birch (Betula pendula) seedling roots and shoots were investigated. Visual inspection of dark discoloration, direct PCR and re-isolation, and detailed root morphology analyses were used to evaluate the effects of Phytophthora inoculation on roots. Symptoms in leaves and stems were also recorded. Phytophthora was successfully re-isolated from 67% of the surface-sterilized roots of inoculated seedlings, but not from the non-inoculated control seedlings. Dark discolorations were found more often in the root segments of inoculated seedlings than in control seedlings. In the Phytophthora-treated seedlings, discoloured root segments were usually linked and found primarily in the main root or lateral roots attached to it, whereas in the control seedlings a few single discoloured root segments were scattered throughout the root systems. The number of root segments was lower in the inoculated than in the control seedlings, indicating root loss after Phytophthora inoculation. In the shoots of inoculated birches, leaf and shoot wilting was observed. The appearance of wilting in shoots without visible dark discoloration in the base of stems indicated that symptoms originated from roots inoculated with Phytophthora.

Isolation and characterization of plant growth-promoting rhizobacteria and their effects on the growth of Medicago sativa L. under salinity conditions.

Plant growth-promoting rhizobacteria are a group of free-living bacteria that colonize plant rhizosphere and benefit plant root growth, thereby increasing host plant to cope with salinity induced stress. The aim of this study was to (1) isolate and characterize auxin-producing bacteria showing a high plant growth-promoting (PGP) potential, and (2) evaluate the PGP effects on the growth of Medicago sativa L under salinity stress (130mM NaCl). Of thirteen isolates, Bacillus megaterium NRCB001 (NRCB001), B. subtilis subsp. subtilis NRCB002 (NRCB002) and B. subtilis NRCB003 (NRCB003) had the ability to produce auxin, which ranged from 47.53 to 154.38μgml-1. The three auxin-producing bacterial strains were shown multiple PGP traits, such as producing siderophore and NH3, showing ACC deaminase activity, solubilize phosphate and potassium. Furthermore, NRCB001, NRCB002, and NRCB003 could survive in LB medium containing 1750mM NaCl. The three auxin-producing with salinity tolerance strains were selected for further analyses. In greenhouse experiments, when inoculated with NRCB001, NRCB002 and NRCB003, dry weight of alfalfa significantly (P < 0.05) increased by 24.1%, 23.1% and 38.5% respectively, compared with those of non-inoculated control seedlings under normal growth condition. When inoculated with NRCB002 and NRCB003, dry weight of alfalfa significantly (P < 0.05) increased by 96.9 and 71.6% respectively, compared with those of non-inoculated control seedlings under 130mM NaCl condition. Our results indicated that NRCB002 and NRCB003 having PGP traits are promising candidate strains to develop biofertilizers, especially used under salinity stress conditions.

Unravelling the role of drought as predisposing factor for Quercus suber decline caused by Phytophthora cinnamomi

Drought has been assumed as a predisposing factor in the decline caused by Phytophthora cinnamomi on Mediterranean Quercus forests, enhancing cork oak susceptibility to the root infection. However, P. cinnamomi outbreaks appear associated to waterlogged soils, with infections being particularly successful when soil moisture content fluctuates from flooding to water deficiency. We obtained cork oak seedlings potentially predisposed to Phytophthora disease by exposing them to a short (3 weeks) or a long (6 weeks) drought. These seedlings subjected to drought, together with well-watered seedlings, were exposed to two different soil concentrations of P. cinnamomi inoculum (chlamydospores) and submitted to high soil humidity for 4 weeks. Values of root necrosis were significantly higher in inoculated oak seedlings compared to non-inoculated control seedlings, but no significant differences were observed depending on previous drought treatments. Consequently, drought cannot be considered as a predisposing factor required for Phytophthora root disease development in cork oaks; although the adverse effects of both factors (drought and Phytophthora root infections) likely have synergistic consequences in the decline and death of affected oaks.

Amelioration of heavy metal stress by endophytic Bacillus amyloliquefaciens RWL-1 in rice by regulating metabolic changes: potential for bacterial bioremediation.

This study aimed to investigate the bioremediation efficiency of phytohormone-producing endophytic Bacillus amyloliquefaciens RWL-1 isolated from rice seeds. In this study, we tested RWL-1 against various heavy metals (Cu, Cr, Pb, and Cd). Among the tested heavy metals, RWL-1 showed the highest tolerance for Cu stress and we observed alterations in growth kinetics with various Cu concentrations (1, 2.5, and 5 mM). We confirmed the biosorption potential of RWL-1 by scanning electron microscopy coupled with energy-dispersive X-ray spectrometry showing that Cu ions were adsorbed on RWL-1 cell surfaces. We further tested RWL-1 for its plant growth promoting and stress reliance efficiency in response to a dose-dependent increase in soil Cu (1, 2.5, and 5 mM). The RWL-1 inoculation significantly increased seedling biomass and growth attributes compared with non-inoculated control seedlings with and without Cu stress. Moreover, RWL-1 inoculation significantly promoted a physiochemical response in seedlings with and without Cu stress by reducing Cu uptake, improving carbohydrate levels (glucose, sucrose, fructose, and raffinose), enhancing amino acids regulation, and augmenting antioxidant levels (POD, PPO, and GHS). Levels of stress-responsive phytohormones such as abscisic acid (ABA) and jasmonic acid were significantly reduced in RWL-1-inoculated seedlings as compared with non-inoculated control seedlings under normal condition and same levels of Cu stress. In conclusion, the inoculation of B. amyloliquefaciens RWL-1 can significantly improve plant growth in Cu-contaminated soil and reduce metal accumulation, thus making plants safer for consumption. This approach could be tremendously helpful for safe and sustainable agriculture in heavy metal-contaminated areas.

Flowering Dogwood Infections with Macrophomina phaseolina

Macrophomina phaseolina was isolated from the crown region and roots of mature flowering dogwood (Cornus florida L.) trees in the landscape and nursery plantings. Although this pathogen has been reported in Cornus species, its occurrence and impact on C. florida has not been reported. Pathogenicity tests were conducted on dogwood seedlings, and all inoculated seedlings developed root necrotic lesions and no small lateral roots, whereas the non-inoculated control seedlings remained disease-free and developed numerous small roots. Seedlings inoculated with M. phaseolina exhibited numerous microsclerotia, but non-inoculated seedlings did not. In greenhouse experiments, plants inoculated on the stems near the soil line developed brown canker-like lesions and swellings around the inoculated area. These were not observed on non-inoculated plants.

Growth stimulation of barley and biocontrol effect on plant pathogenic fungi by a Cellulosimicrobium sp. strain isolated from salt-affected rhizosphere soil in northwestern Algeria

The plant growth promoting effect of bacterial isolates from salt-affected agricultural rhizospheric soil from Bejaia, Algeria, on barley seedlings as well as biological control abilities of these isolates against phytopathogenic fungi were determined. Four isolates stimulated significantly germination and growth of barley seedlings in an axenic test system and in soil pots. Isolate S16 (Cellulosimicrobium sp.) stimulated the growth of barley seedlings by 185% (stem height of 13.0 ± 0.11 cm) over non-inoculated control seedlings (7.0 ± 0.12 cm). Cellulosimicrobium sp. S16 was found also superior in mycelial growth inhibition assays against the plant pathogenic fungi Botrytis cinerea, Fusarium oxysporum and Verticillium dahliae. Furthermore, several plant growth promoting traits (production of indole acetic acid, inorganic phosphate solubilization, siderophore production) and production of enzymes beneficial for soil fertility (protease, chitinase, amylase and urease) were identified. However, no evidence for nitrogen fixation was found by testing acetylene reduction and the presence of nif-genes. Based on comparative sequence analysis of almost full length 16S-rRNA coding gene fragments, Cellulosimicrobium sp. S16 exhibits the highest similarity of 99.7% to Cellulosimicrobium cellulans (accession number AY665978). Cellulosimicrobium sp. S16 could be a successful candidate for the application as a plant growth promoting inoculant.

Piriformospora indica rescues growth diminution of rice seedlings during high salt stress

Piriformospora indica association has been reported to increase biotic as well as abiotic stress tolerance of its host plants. We analyzed the beneficial effect of P. indica association on rice seedlings during high salt stress conditions (200 and 300 mM NaCl). The growth parameters of rice seedlings such as root and shoot lengths or fresh and dry weights were found to be enhanced in P. indica-inoculated rice seedlings as compared with non-inoculated control seedlings, irrespective of whether they are exposed to salt stress or not. However, salt-stressed seedlings performed much better in the presence of the fungus compared with non-inoculated control seedlings. The photosynthetic pigment content [chlorophyll (Chl) a, Chl b, and carotenoids] was significantly higher in P. indica-inoculated rice seedlings under high salt stress conditions as compared with salt-treated non-inoculated rice seedlings, in which these pigments were found to be decreased. Proline accumulation was also observed during P. indica colonization, which may help the inoculated plants to become salt tolerant. Taken together, P. indica rescues growth diminution of rice seedlings under salt stress.

Stem Canker of Giant Dogwood (Cornus controversa) Caused by Fusarium lateritium in Korea.

In May 2012, a stem canker was observed on a ~20-year-old giant dogwood (Cornus controversa) in Suwon, Gyeonggi Province, South Korea, which consisted of necrotic lesions on stem bark with orange sporodochial fruiting bodies. A single fungal colony was obtained from hyphal tips that were grown out of affected tissues plated on potato dextrose agar (PDA) acidified with 0.1% lactic acid after surface sterilization with 1.0% NaOCl for 30 s and 70% ethanol for 30 s, and incubated at 25°C for 7 days in the dark. The fungal isolate was grown on PDA and carnation leaf agar (CLA) to examine its mycological characteristics. The fungal colonies grown on PDA at 25°C for 7 days had diameters of 31 to 36 mm, with the colony surface sparsely cottony or with little or no aerial mycelium, very pale brown to pink, becoming progressively lighter toward the center; the colony reverse was pinkish-white to reddish-yellow, producing very few hyaline microconidia that were ellipsoidal, mostly 1-celled, and 15.4 to 22.8 × 4.1 to 4.8 μm. It produced hyaline macroconidia that were slightly curved, frequently 3 septate, a hooked or beaked apical cell and a foot-shaped or notched basal cell, 28.0 to 35.5 × 4.0 to 5.5 μm, borne on pink sporodochia. On CLA, the colony surface was lighter toward the center with no or sparse aerial mycelium, growing to 33 to 43 mm diameter at 25°C for 7 days. Microconidia were ellipsoidal, mostly 1-celled, and 9.2 to 17.5 × 2 to 2.5 μm on CLA. Macroconidia were produced on pink sporodochia near or on carnation leaf pieces, falcate to almost straight or slightly curved, frequently 5 to 7 septate, with a hooked or beaked apical cell and a foot-shaped or notched basal cell, and 45.5 to 59 × 5.5 to 6.5 μm. Chlamydospores were rare or absent. Based on these morphological characters, the isolate was identified as Fusarium lateritium (1,2). Sequences of the internal transcribed spacer (ITS) rDNA region of the fungus (GenBank Accession No. KC453998) amplified using primers ITS1/ITS4 had 100% sequence identity to F. lateritium (JN198452). The DNA sequences of translation elongation factor-1α (EF-1α) amplified using primers EF1/EF2 (KC453997) also had 100% sequence identity to F. lateritium (AY707172 and AY707156). The culture was deposited in the Korean Collection for Type Cultures (KCTC 46029). Pathogenicity tests were conducted using 1-year-old giant dogwood seedlings grown for 3 weeks before inoculation in a 1:1:1 mixture of peat moss, perlite, and sand in 10" × 10" × 12" plastic pots. The stems of three seedlings were inoculated with the mycelial plugs from the edge of the fungal culture on PDA grown at 25°C for 7 days, which were placed on three barkless cuts per stem and sealed with Parafilm that was removed 3 weeks later. Canker symptoms on the inoculated seedlings developed after 30 days of incubation at 25 to 32°C and relative humidity of 50 to 60% in a glasshouse, from which the same fungus was isolated. Non-inoculated control seedlings showed no canker development. To our knowledge, this is the first report of stem canker on giant dogwood caused by F. lateritium in Korea and also the family Cornaceae as new host for the fungus.

First Report of Vinca Blight Caused by Phytophthora nicotianae in Northwestern Mexico.

Vinca (Catharantus roseus (L.) G. Don) is a common ornamental landscape plant. From July to September 2012, blighted and wilted vinca plants were found in retail stores, commercial nurseries, and urban landscape areas of Culiacan, Sinaloa, in northwestern Mexico. In several commercial nurseries and a retail store, incidence of the unknown disease on vinca plants ranged from 20 to 50%, resulting in significant economic losses. Symptoms of the disease started with a foliar blight, and if warm and wet conditions were present, the disease progressed, causing plant wilting and death. Surface-sterilized (0.5% NaOCl 1 min) diseased plant tissue was plated on V8 agar medium, and after 72 h of incubation at 25°C, white colonies of coenocytic mycelium were developed from the plated tissues. Isolates produced cottony colonies on V8 agar medium, grew well between 7 and 30°C (optimum of 25°C), and produced spherical, intercalary, and terminal chlamydospores (17 to 30 μm) and non caducous, papillate, spherical to ovoid sporangia of 30 to 39 × 21 to 31 μm. Based on these morphological characteristics, Phytophthora isolates were identified as Phytophthora nicotianae Breda de Haan (1,3). The identity of two representative isolates OV4 and OV11 was confirmed by sequence analysis of the rDNA internal transcribed spacers (ITS; GenBank Accession Nos. KC248202 and KC248201), and of the β-tubulin (β-tub; KC248404 and KC248403) and translation elongation factor 1-α (EF1-α; KC248206 and KC248205) genes. Comparative sequence analysis against the NCBI nucleotide database showed a high degree of identity with reference sequences of P. nicotianae (ITS, 99%; β-tub, 99%; EF1-α, 100%) (2). A pathogenicity test with a representative isolate of P. nicotianae was performed on 10-week-old healthy vinca seedlings (n = 10). An aliquot of 10 ml of a zoosporic suspension (104 zoospores/ml) was sprayed onto the seedlings' leaves. An equal number of non-inoculated control seedlings were sprayed with sterile distilled water. Seedlings were maintained in a moist chamber at 25°C with 80 to 90% relative humidity and watered as needed with sterile water. Inoculated plants showed initial symptoms of foliar blight after 4 days, whereas control plants remained healthy. Ten days after inoculation, inoculated plants showed severe wilting. P. nicotianae was reisolated only from inoculated plants, thus fulfilling Koch's postulates. To our knowledge, this is the first report of P. nicotianae attacking annual vinca in northwestern Mexico.

English

Three bacterial strains (Pseudomonas&nbsp;species, P1;&nbsp;Pseudomonas mendocina, P2; andStenotrophomonas maltophilia, S3) were investigated in this study to assess their growth stimulatory effects on&nbsp;Triticum aestivum&nbsp;plants. These strains are Gram negative, motile, aerobic rods with catalase and oxidase positive. In general, seed inoculations of these bacteria (mono and mixed cultures) promoted germination, early growth parameters, auxin content, soluble protein content, peroxidase and acid phosphatase activity relative to non-inoculated control seedlings. Mixed cultures inoculations resulted in some decrease in various growth parameters. Almost&nbsp;15 to 43%&nbsp;decrease in dry weight of plants was observed as compared to non-inoculated control. Bacterial inoculation (Pseudomonassp., P1) resulted in significantly higher acid phosphatase (40%) and peroxidase (39.7%)contents of plant when compared with non-inoculated control. Mixed culture combination showed pronounced synergistic effects relative to respective monocultures. &nbsp; Key words:&nbsp;Pseudomonas,&nbsp;Triticum aestivum, auxin, acid phosphatase, peroxidase,Stenotrophomonas.

English

In the present study mono and mixed culture bacterial combinations of Azotobacter were used to inculcate&nbsp;Vigna radiata&nbsp;seeds. In general, bacterial inoculations (mono and mixed cultures) promoted seed germination, early growth parameters, auxin content, soluble protein content, peroxidase and acid phosphatase activity relative to non-inoculated control seedlings. Increase of (23%) as well as decrease (6.8%) in the root length were observed with bacterial inoculations relative to non-inoculated seedlings. About 20.07% enhancements in fresh weight and 62% enhancement in dry weight was observed in case of bacterial inoculations. Among the monoculture Ab-4(A3) induced pronounced growth stimulator effects, mixed culture combinations B6, B7, and B10 showed pronounced synergistic effects relative to respective monocultures, while B2 exhibited negative in majority of the parameters being studied. &nbsp; Key words:&nbsp;Azotobacter,&nbsp;Vigna radiata,&nbsp;auxin, acid phosphatase, peroxidase. .

Plant growth promoting characteristics of soil yeast (Candida tropicalis HY) and its effectiveness for promoting rice growth

Compared with bacteria and mycorrhizal fungi, the potential to use yeasts as plant growth promoting agents has been under-exploited. We investigated the ability of the soil yeast Candida tropicalis HY (CtHY) to stimulate rice seedling growth and some of the possible mechanisms by which plant interaction may occur. Laboratory culture experiments found that CtHY produces small quantities of indole acetic acid (IAA), but grows rapidly on aminocyclopropane-1-carboxylate (ACC) as a sole source of nitrogen, indicative of high ACC deaminase activity. The strain also tested positive for polyamine and phytase production, and mobilized phosphate from insoluble tri-calcium phosphate. CtHY rapidly colonized the roots of rice seedlings and maintained high numbers for at least 3 weeks, increasing the dry weight of inoculated roots by 16–35% compared to non-inoculated control seedlings. These results validate the inclusion of CtHY in the commercial biofertiliser product BioGro, which has previously been demonstrated to increase the nutrition, growth and yield of paddy rice.

Symbiotic and synergistic efficacy of endomycorrhizae with Dendrocalamus strictus L.

&amp;nbsp; The present investigation was undertaken to find out efficient strains of arbuscular mycorrhiza (AM fungi) alone or in combinations with Trichoderma viride for inoculation Dendrocalamus strictus L. seedlings. The inoculated seedlings showed good response having higher plant height, phosphorous ions content in root and shoot, AM spore number and root colonization than non-inoculated (control) seedlings in both single (alone) and co-inoculation (combined consortium) experiments. T. viride showed significant growth followed by Glomus mosseae, G. fasciculatum and mixed AM with single inoculation. In co-inoculation, the best growth responses were observed with G. fasciculatum + T. viride followed by G. mosseae + T. viride, mixed vesicular arbuscular mycorrhizas (VAM) + T. viride, G. mosseae + G. fasciculatum + T. viride + mixed VAM, G. mosseae + G. fasciculatum + T. viride and G. mosseae + G. fasciculatum after 120 days and also depicted maximum increase in phosphorus content of shoot and root when compared with other inoculated seedlings. However, all the inoculated seedlings showed significant increase in phosphorus content when compared with control seedlings.

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.

Two-year field performance of lodgepole pine seedlings: Effects of container type, mycorrhizal fungal inoculants, and site preparation

Interior lodgepole pine (Pinus contorta var. latifolia) seedlings were grown in Styroblocks™, Copperblocks™, or AirBlocks™, and inoculated with Rhizopogon rubescens or Hebeloma longicaudum, or left as noninoculated controls. Seedlings were planted into different rooting environments in two separate locations, encompassing two separate experiments. In experiment 1, seedlings were planted into fully rehabilitated landings (ripped with burn-pile debris and topsoil incorporated), ripped landings, and unprepared cutblocks in the spring. In experiment 2, seedlings were planted in a cutblock in manually screefed (i.e., boot screefed) planting sites or undisturbed forest floor planting sites in the summer. Seedlings in the fully rehabilitated landings were 21% taller, had 45% larger diameters, and were more vigorous than seedlings in landings that were simply ripped; seedlings planted in the unprepared cutblock were taller, but with a smaller diameter, than those on the rehabilitated landings. Seedlings in screefed microsites grew significantly larger (5%) than seedlings planted directly in the forest floor. After 2 years in the field, the sizes of spring-planted, noninoculated seedlings, and seedlings inoculated with ectomycorrhizal fungi were not significantly different. Inoculated summer-planted seedlings were approximately 5% larger than non-inoculated control seedlings. Among the variables we manipulated, planting environment had the greatest influence on seedling growth.

First Report on the Occurrence of Bacterial Stripe Organism Acidovorax avenae subsp. avenae in Rice Seeds from Burkina Faso.

Breeder rice seeds from Burkina Faso harvesteds in 1999 were tested for Acidovorax avenae subsp. avenae. This pathogen affects rice, maize, sorghum, and other Gramineae. Ten samples of 200 seeds in each sample were tested by the cassette holder method for detection of this bacterium (1). Seedlings were evaluated for symptom development after 14 days at 27 to 30°C and 100% relative humidity under fluorescent light (12 h photoperiod). Bacterial stripe symptoms were observed in seedlings raised from 9 of 10 seed samples tested, and incidence ranged from 5 to 20%. Diseased seedlings showed water-soaked areas on coleoptiles and brown stripes on leaf sheaths and mid-ribs. Twenty-six strains obtained from diseased seedlings were characterized using several criteria. Colonies were small, whitish-grey, raised, entire and translucent on nutrient agar and cream-tan, raised, entire, and did not produce fluorescent pigment on King's medium B. They were Gram negative, oxidase positive and nitrate positive. Variable reactions were recorded for starch hydrolysis; 22 strains reacted positively and 4 negatively. All 26 strains reacted positively in ELISA performed with antiserum against A. avenae subsp. avenae. Results using Biolog GN MicroPlates (Biolog Inc., Hayward, CA computer identification system, Release 4.0) showed all strains to be A. avenae subsp. avenae (sim. 0.709 to 0.802). Hypersensitive reactions on leaves of 2-month-old tobacco plants infiltrated with bacterial suspensions were recorded within 24 h. Strains were tested for pathogenicity by injecting stems of 21-day-old rice plants with bacterial suspensions (approximately 108 CFU/ml). Inoculated seedlings were incubated for 4 to 7 days under humid conditions at 28°C. Inoculated rice plants showed brown stripes and non-inoculated control seedlings remained symptomless. Based on biochemical, serological, and biological characteristics, strains were identified as A. avenae subsp. avenae. This is the first report of A. avenae subsp. avenae, causal agent of bacterial stripe of rice, in Burkina Faso. The common presence of A. avenae subsp. avenae in breeder rice seeds emphasizes the need for control measures to limit further spread to unaffected rice-growing areas and other cereal crops. Reference: (1) D. D. Shakya et al. Phytopathol. Z. 114:256-259, 1985.

Variation in mycorrhizal development and growth stimulation by 20 Pisolithus isolates inoculated on to Eucalyptus grandis W. Hill ex Maiden.

Twenty isolates of Pisolithus, covering u range of hosts, basidiocarp types and geographic locations were compared on their ability to form mycorrhiza in vitro with Eucalyptus grandis and to stimulate seedling growth in vivo. There was a large variation between isolates in the rate of mycorrhizal development and this was used to categorize isolates into six types. Mycorrhiza of seedlings inoculated with type I isolates were the most advanced with a dual-layered mantle, a fully-developed Harris net and radially elongated epidermal cells. Mycorrhiza of seedlings inoculated with types II V isolates were progressively less advanced so that mycorrhiza of type V isolates had a thin single-layered mantle, the Hartig net was only partially developed and the epidermal cells were not elongated. Root lips of seedlings inoculated with type- VI isolates were non-mycorrhizal. Inoculated seedlings were transplanted directly into undrained pots containing a yellow sand deficient in phosphorus. Growth stimulation of E. grandis seedlings in the glasshouse varied greatly between Pisolithus isolates, with dry weight increases ranging from two to 45 times that of the non-inoculated control seedlings. Extent of mycorrhizal development was positively correlated to growth stimulation in the glasshouse and it is proposed that this could be used as an indicator of isolate aggressiveness and consequently the potential of an isolate to promote tree growth.

90Sr uptake by Pinus ponderosa and Pinus radiata seedlings inoculated with ectomycorrhizal fungi.

Strontium-90 ((90)Sr) is a radionuclide characteristic of fallout from nuclear reactor accidents and nuclear weapons testing. Prior studies have shown that Pinus ponderosa and P. radiata seedlings can remove appreciable quantities of (90)Sr from soil and store it in plant tissue. In this study, we inoculated P. ponderosa and P. radiata seedlings with one of five isolates of ectomycorrhizal fungi. Inoculated and noninoculated (control) seedlings were compared for their ability to remove (90)Sr from an organic growth medium. Seedlings were grown in a growth chamber in glass tubes containing 165 cm(3) of sphagnum peat moss and perlite (1 : 1 (v/v)) and, except in the controls, the fungal inoculum. After 3 months, 5978 Bq of (90)Sr in 1 ml of sterile, distilled, deionized water was added. Seedlings were grown for an additional month and then harvested. P. ponderosa seedlings with ectomycorrhizae accumulated 3.0-6.0% of the (90)Sr; bioconcentration ratios (Bq (90)Sr cm(-3) plant tissue/Bq (90)Sr cm(-3) growth medium) ranged from 98-162. Ectomycorrhizal P. radiata seedlings accumulated 6.0-6.9% of the (90)Sr; bioconcentration ratios ranged from 88-133. Nonmycorrhizal P. ponderosa and P. radiata seedlings accumulated only 0.6 and 0.7% of the (90)Sr and had bioconcentration ratios of 28 and 27, respectively. Ectomycorrhizal P. ponderosa and P. radiata seedlings are able to remove 3-5 times more (90)Sr from contaminated soil than seedlings without ectomycorrhizae.

Variation in field response of Pinussylvestris to nursery inoculation with four different ectomycorrhizal fungi

Pinussylvestris L. seedlings were inoculated in nursery containers with the assertive mycorrhizal formers Laccarialaccata (Scop, ex Fr.) Bk. &amp; Br., Hebelomacrustuliniforme (Bull, ex Fr.) Quélet, and Cenococcumgeophilum Fr. After outplanting, seedling size and the frequency of mycorrhizal root tips were monitored over 6 years. Between 25 and 90% of the root tips of inoculated seedlings were mycorrhizal with the target fungi at outplanting, whereas the noninoculated control seedlings were spontaneously colonized by other fungi at rates between 25 and 50%. After 1.5 years the inoculated fungi were still present on the roots; however, they were slowly being replaced by indigenous forest species. In the nursery, most of the inoculations resulted in reduced seedling growth. This inhibition of growth rate was pronounced up to 1.5 years in the field, except for seedlings inoculated with C. geophilum. By this time, L. laccata and H. crustuliniforme inoculated seedlings were about 40 to 50% smaller in volume than the control seedlings, and the relative difference in size was maintained or slightly decreased during the following 4 years. The noninoculated nursery production seedlings were about 50% larger in volume than the corresponding control seedlings at outplanting. In the field, however, they grew relatively slower and consequently, were soon similar in volume to the control seedlings.