Growth Promotion Of Seedlings Research Articles

Growth of Nursery-grown Bamboo Inoculated with Arbuscular Mycorrhizal Fungi and Plant Growth Promoting Rhizobacteria in two Tropical Soil Typeswith and without Fertilizer Application

A nursery experiment was conducted to assess the effect of bioinoculants (Glomus aggregatum, Bacillus polymixa, Azospirillum brasilense) on seedling growth promotion of bamboo (Dendrocalamus strictus (Roxb.) Nees.) in two soil types (alfisol, vertisol) with or without fertilizer application. Bamboo seedlings were grown in the presence or absence of bioinoculants either individually or in all combinations for 180 days in field soil under tropical nursery conditions. Shoot, rhizome and root length, dry masses, nutrient concentrations and arbuscular mycorrhizal (AM) colonized root lengths were determined at harvest. Under the experimental condition tested combined inoculation of AM fungi, PSB and A. brasilense resulted in maximum growth response both under fertilized and unfertilized conditions in both soil types. Fertilizer application enhanced the efficiencies of N, P and K uptake, whereas reduced their usage efficiencies. Though soil type did not affect microbial inoculation response, fertilizer application significantly affected plant response to microbial inoculation.

Rhizobacteria Isolated from Loblolly Pine Seedlings Mediate Growth-Promotion of Greenhouse-Grown Loblolly, Slash, and Longleaf Pine Seedlings

Abstract Loblolly (Pinus taeda L.), slash (Pinus elliottii Engelm.), and longleaf pine (Pinus palustris Mill.) seeds were inoculated in the greenhouse with rhizobacteria recovered from 4-month-old bareroot loblolly pine seedlings. Emergence and seedling densities were determined at 3- and 8-week intervals after sowing, respectively, with root and shoot biomass measured at 12 weeks. All bacterial strains significantly increased the speed of seedling emergence relative to untreated loblolly and slash pine seeds, while five strains significantly slowed longleaf germination. For loblolly and slash pine, there were no differences in percentage germination when comparing treated and untreated seed. However, all bacterial strains significantly reduced longleaf germination over nontreated seed. Treatment with rhizobacteria had significant positive and negative effects on seedling growth and biomass, depending on the tree species and bacteria isolate used. Five of the eight bacterial isolates tested increased shoot length of loblolly pine seedlings, whereas one strain increased above- and belowground biomass. Slash pine seedlings experienced growth increases with three bacterial strains. However, two bacterial strains, ALA-41G and ALA-54G, resulted in shorter slash pine shoots. Only strain ALA-3G increased shoot biomass of longleaf pine over nontreated longleaf seed. Increased seedling emergence and growth promotion by rhizobacteria collected from Pinus sp. is a potential useful tool for management of these forest species. The effect may be species-specific and the use of bacteria in forest nurseries for growth promotion will need to take this into account. FOR. SCI. 51(6):541–545.

Promotion of Seedling Growth of Seeds of Rice (Oryza sativa L. cv. Hitomebore) by Treatment with H2O2 before Sowing

High germinability of seeds and establishment of young seedlings in rice (Oryza sativa L.) are necessary for direct seeding in paddy fields. We investigated whether germinability and seedling growth were promoted by treatment of rice seeds (cv. Hitomebore) with hydrogen peroxide solution (H2O2) during the imbibition for 24 h. H2O2 treatment with 50 mM H2O2 promoted seed germination, and seedling growth (shoot length, root length and shoot fresh weight) in agar culture under a low temperature condition (18°C day/14°C night). Seedling growth was promoted by H2O2 treatment not only under the low-temperature condition but also under a normal (23°C day/18°C night) temperature condition. Furthermore, H2O2 treatment promoted seedling growth under a flooding condition in a greenhouse. These results suggest that H2O2 treatment of rice seeds during the imbibition is advantageous for direct seeding. We discussed the relation between the promotion of the seed germinability and the seedling growth under a low-temperature condition, and the expression of some genes encoding ROS scavenger enzymes induced by H2O2 treatment.

Microbial populations and activities in the rhizoplane of rock-weathering desert plants. II. Growth promotion of cactus seedlings.

Four bacterial species isolated from the rhizoplane of cacti growing in bare lava rocks were assessed for growth promotion of giant cardon cactus seedlings (Pachycereus pringlei). These bacteria fixed N(2), dissolved P, weathered extrusive igneous rock, marble, and limestone, and significantly mobilized useful minerals, such as P, K, Mg, Mn, Fe, Cu, and Zn in rock minerals. Cardon cactus seeds inoculated with these bacteria were able to sprout and grow normally without added nutrients for at least 12 months in pulverized extrusive igneous rock (ancient lava flows) mixed with perlite. Cacti that were not inoculated grew less vigorously and some died. The amount of useful minerals (P, K, Fe, Mg) for plant growth extracted from the pulverized lava, measured after cultivation of inoculated plants, was significant. This study shows that rhizoplane bacteria isolated from rock-growing cacti promote growth of a cactus species, and can help supply essential minerals for a prolonged period of time.

Bacterização de sementes e desenvolvimento de mudas de pepino

Bactérias epifíticas e endofíticas foram isoladas de plantas de pepino sadias, coletadas em diversos municípios do estado de Pernambuco e avaliadas na promoção de crescimento de plântulas em casa de vegetação. Foram realizados três bioensaios. No primeiro, foram testados 93 isolados; no segundo, 32 isolados e; no terceiro, oito isolados de pepino e mais 10 isolados provenientes de outras culturas. As sementes de pepino foram bacterizadas por imersão na suspensão bacteriana ajustada à concentração de A580 = 0,7, semeadas em substrato orgânico contido em bandejas de isopor; mantidas em casa de vegetação e, analisadas dez dias após a semeadura quanto às matérias secas da parte aérea (MSPA), raiz (MSR) e total (MST). No último bioensaio, os isolados epifíticos PEP52, PEP8, PEP82, PEP91 e C22 foram selecionados por aumentarem significativamente a MSR e MST das plântulas em relação à testemunha, com valores superiores a 70 e 40%, respectivamente. Após o teste de compatibilidade in vitro, esses cinco isolados, testados separadamente e em misturas, aumentaram o índice de MSPA, MSR e MST das plântulas de pepino, sem diferirem significativamente entre si. Os isolados PEP81 (Bacillus amyloliquefaciens) e PEP91 (Enterobacter cloacae) destacaram-se com índices de aumentos de 55,5 e 39,5% (MSPA), 42,9 e 37,2% (MSR) e 41,6 e 34,0% (MST), respectivamente. A produção do ácido indol acético, ácido cianídrico, solubilização de fosfatos e alteração nos teores foliares de N, P, K, Ca e Mg, foram avaliados como possíveis mecanismos de ação desses dois isolados, porém com resultados negativos. A bacterização das sementes com B. amyloliquefaciens PEP81 e E. cloacae PEP91 pode melhorar a qualidade das mudas de pepino.

Growth promotion of red pepper plug seedlings and the production of gibberellins by Bacillus cereus, Bacillus macroides and Bacillus pumilus

The growth of red pepper plug seedlings was promoted by Bacillus cereus MJ-1, B. macroides CJ-29, and B. pumilus CJ-69 isolated from the rhizosphere. Gibberellins (GAs), a well-known plant growth-promoting hormone, were detected in the culture broth of their rhizobacteria. Among the GAs, the contents of GA1, GA3, GA4, and GA7, physiologically active GAs, were comparatively higher than those of others, suggesting that the growth promoting effect was originated from the GAs. This isthe first report on the production of GA5, GA8, GA34, GA44, and GA53 by bacteria.

Isolamento, seleção de bactérias e efeito de Bacillus spp. na produção de mudas orgânicas de alface

Isolados bacterianos epifíticos e endofíticos, obtidos de plantas sadias de alface, foram avaliados para promoção de crescimento de mudas e plantas, respectivamente em estufa e campo de cultivo orgânico (Chã Grande-PE). Nos experimentos em estufa, foi utilizada a cultivar Verônica e em campo, as cultivares Verdinha e Verônica. Os isolados foram aplicados por bacterização simultânea nas sementes e substrato. Em campo, foram utilizados os isolados mais eficientes, C25 (Bacillus thuringiensis subvar. kenyae) e C116 (Bacillus pumilus), separadamente e em mistura, após teste de compatibilidade. Em estufa, foram avaliadas a matéria fresca de raízes (MFR), da parte aérea (MFPA) e total (MFT), 21 dias após a bacterização. Em campo, foi determinado o peso da matéria fresca total de plantas comercializáveis 21 e 28 dias após o transplante, respectivamente para as cultivares Verdinha e Verônica. Os mecanismos de ação de BPCP analisados foram produção de ácido indol acético, ácido cianídrico, solubilização de fosfatos e alterações dos teores foliares dos macronutrientes, N, P, K, Ca e Mg. Em estufa, as mudas apresentaram aumento significativo em relação à testemunha para MFR, MFPA e MFT quando foi utilizado o isolado C116 e para MFR e MFT utilizando-se o C25. No campo, não houve promoção significativa no crescimento nas plantas das cultivares Verdinha e Verônica, tratadas com C25 e C116 separadamente ou em mistura. Dos mecanismos de ação analisados verificou-se apenas elevação significativa (P=0,05) do teor foliar de N pelo isolado C25.

고추 플러그묘 초기 생육을 촉진시키는 Bacillus amyloliquefaciens MJ-3의 분리 및 상토내 처리 효과

본 연구에서는 가지과 작물의 근권에서 유용한 균주를 분리하고 근권ㆍ길항ㆍ생육촉진미생물을 선별ㆍ제제화하고 상토에 첨가하여 미생물제제 혼입 상토를 제조한 후 고추 플러그묘의 초기 생장에 미치는 영향을 조사하였다. 근권미생물로는 가지과 작물의 뿌리 및 재배 토양 등 385점의 균원시료로부터 540여점을 분리한 후, 가지과 작물에 공통적으로 발생되는 Alternaria solani, Botrytis cinerea, Fusarium oxysporium, Phytophthora capsici, Sclerotinia sclerotiorum 등의 병원균에 높은 길항력을 가진 미생물 20여종을 선발하고, 이들 길항미생물 중에서 고추의 초기 생육을 촉진시키는 MJ-3균주를 최종 선발하였다. 근권ㆍ길항ㆍ생육촉진미생물인 분리주 MJ-3은 Bergey's manual of systematic bacteriology의 방법과 16S rDNA sequence법 등으로 조사하여 Bacillus amyloliquefaciens동정하였다. 제제화한 B. amyloliquefaciens를 상토에 첨하여 미생물 혼입 상토를 제조하였고, 이를 이용하여 재배한 고추 플러그 묘는 초장과 경경, 뿌리길이, 생체중량 등이 모두 대조구에 비해 소량 증가되었으나, 특히 뿌리의 생체중량이 대조구가 0.61g/plant인데 비해 시험구는 0.88g/plant로 44.3% 증가하였다. 미생물제제 첨가 상토에서 재배한 고추의 gib-berellin (GA<TEX>$_1$</TEX>) 함량은 0.559ng/g(건조중량)이었다. The effect of useful rhizobacterium added in bed soil on the early growth promotion of red pepper plug seedlings was investigated. Total 540 colonies of rhizobacteria from 385 samples of eggplant family roots were isolated. Among these, 5 isolates were selected for antifungal activity against pathogenic fungi such as Alternaria solani, Botrytis cinerea, Fusarium oxysporium, Phytophthora capsici, and Sclerotia sclerotiorum. Of all the isolates, MJ-3 having the most pronounced growth-promoting ability for red pepper was finally selected and identified as Bacillus amyloliquefaciens through characterization of biochemical and bacteriological aspects and 16S rDNA sequence. The plant height, stem diameter, root length and fresh weight of red pepper plants which were grown with inoculation of B. amyloliquefaciens MJ-3 were higher than those without inoculation. Especially the root weight of the inoculated red pepper plant increased by 44.3%, the content of endogenous plant hormone (CA<TEX>$_1$</TEX>) being 0.556 ng/g (dry weight).

Influence of Microbial Inoculations on Cedrus deodara in Relation to Survival, Growth Promotion and Nutrient Uptake of Seedlings and General Soil Microflora

Selected microorganisms (Laccaria laccata, Trichoderma viride, Bacillus subtilis, Pseudomonas corrugata and Azotobacter chroococcum) were used as inoculants to study their influence on seed germination, seedling survival and subsequent growth in Cedrus deodara. The microbial inoculations positively affected these parameters over control, in the following order: Azotobacter chroococcum Pseudomonas corrugata Bacillus subtilis Trichoderma viride Laccaria laccata.The major cause of seedling mortality was found to be (1) wilting of emerged seedlings by Fusarium oxysporum, and (2) cutworm attack. Bacterial inoculations were found to be superior in suppressing the proliferation of Fusariumsp., thereby enhancing seedling survival. One of the bacterial inoculants, B. subtilis, resulted in 76% seed germination, compared to 54% in control. Though inoculation with L. laccataresulted in maximum mycorrhizal infection (up to 72%) compared to48%in control seedlings, it afforded least protection against Fusariumsp., as well as minimal growth promotion. On the other hand, inoculation with T. viridesignificantly controlled wilting of seedlings and improved plant growth. Microbial inoculations were found to influence the soil microflora, nutrient status of the rhizosphere soil and that of different parts of seedlings. Enrichment of carbon was recorded in the rhizosphere soil. Enhanced nitrogen, phosphorus and potassium content of various plant parts indicated a positive influence also on nutrient uptake. The present study has implications for large scale forestry programs.

Suppression of damping-off in maize seedlings by Pseudomonas corrugata

Two strains of Pseudomonas corrugata, (1 and 7), isolated from subtropical and temperate soils in Sikkim Himalaya, respectively, were subjected to Petri-dish as well as plant-based bioassay to examine their potential for disease suppression against three major pathogens of maize. A mixture of Pythium ultimum, P. arrhenomanes and Fusarium graminearum was introduced in the soil; maize seed inoculated with one of the two strains of Pseudomonas corrugata (1 or 7) were sown in pots containing such soil. The bacterial inoculation resulted in significant disease suppression as well as growth promotion of seedlings. The bacterial strains were also evaluated for their intrinsic antibiotic resistance against a range of concentrations of ten antibiotics. While the bacteria were found to be sensitive to gentamycin and rifampicin, they exhibited resistance against ampicillin, carbenicillin and penicillin, even at high concentrations.

Endophytic colonization and field responses of hybrid spruce seedlings after inoculation with plant growth-promoting rhizobacteria

Bacterial colonization and growth responses of hybrid spruce ( Picea glauca × engelmannii) seedlings after inoculation with plant growth-promoting rhizobacteria (PGPR) were evaluated in controlled environment and field assays. Six antibiotic-resistant bacterial strains belonging to the genera Bacillus and Pseudomonas were used as inocula. For controlled environment assays, surface sterilized seeds were inoculated with log 6 Bacillus or log 8 Pseudomonas colony-forming units (cfu) under gnotobiotic conditions for assessment of rhizosphere and internal root and stem tissue colonization. In the field trial, one-year-old, container-grown hybrid spruce seedlings were inoculated with each of the Bacillus or Pseudomonas strains 1–2 days before planting at nine field sites in British Columbia and Alberta, Canada. All six strains colonized the rhizosphere with log 5.6−7.6 cfu g −1 root tissue under controlled environmental conditions. Two strains, Bacillus Pw-2R and Pseudomonas Sm3-RN, were also recovered from internal root and stem tissues with population sizes ranging from log 3.9 to log 5.0 cfu g −1 plant tissue. In the field trial, PGPR survived the winter in the rhizosphere with populations of log 2 to log 5 cfu g −1 root tissue 17 months after inoculation. In addition, spruce growth was significantly enhanced by bacterial inoculation at certain sites. The most effective growth-promoting strains were the endophytes, Sm3-RN and Pw2-R, and the external root colonizing strain, Ss2-RN. These three strains increased seedling dry weight up to 57% above noninoculated controls at five of the nine outplanting sites. Pseudomonas strain Sw1 and the other two Bacillus strains produced mean spruce dry weight increases at four of the sites. Seedling growth inhibition due to bacterial inoculation was detected at some sites. Our results confirm the short-term, site specific effectiveness of PGPR for reforestation of conifer seedlings, and indicate that benefits of a single inoculation at planting can extend through the second year in the field. In addition, bacteria capable of colonizing the seedling interior may be more effective PGPR for spruce than those restricted to the rhizosphere and the root surface. However, site specific seedling growth promotion may necessitate matching PGPR strains to outplanting sites for effective growth promotion.

Colonization and growth promotion of outplanted spruce seedlings pre-inoculated with plant growth-promoting rhizobacteria in the greenhouse

Seeds of two hybrid spruce (Picea glauca (Moench) Voss × Picea engelmannii Parry ex Engelm.) ecotypes were inoculated with one of six plant growth-promoting rhizobacteria (PGPR) strains previously shown to be able to stimulate spruce growth in controlled environments. The resulting seedlings were grown in the greenhouse for 17 weeks before outplanting at four reforestation sites. Inoculation with five of the six strains caused significant seedling growth promotion in the greenhouse, which necessitated analysis of relative growth rates (RGR) to evaluate seedling performance in the field. Four months after outplanting, most strains enhanced spruce shoot or root RGRs in the field, but seedling growth responses were strain specific. For example, Pseudomonas strain Ss2-RN significantly increased both shoot and root RGRs by 10-234% at all sites, but increases of 28-70% were most common. In contrast, Bacillus strain S20-R was ineffective at all outplanting sites. In addition, seedlings inoculated with four of the six strains had significantly less shoot injury than control seedlings at all sites. Evaluation of root colonization by PGPR indicated that bacterial population declines were not related to spruce growth response variability in the field. Our results indicate that once plant growth promotion is induced in the greenhouse, seedling RGR can increase by more than 100% during the first growing season in the field. However RGR increases of 21-47% were more common and may be more representative of the magnitude of biomass increases that can result from PGPR inoculation.

Colonization and growth promotion of outplanted spruce seedlings pre-inoculated with plant growth-promoting rhizobacteria in the greenhouse

Seeds of two hybrid spruce (Picea glauca (Moench) Voss × Picea engelmannii Parry ex Engelm.) ecotypes were inoculated with one of six plant growth-promoting rhizobacteria (PGPR) strains previously shown to be able to stimulate spruce growth in controlled environments. The resulting seedlings were grown in the greenhouse for 17 weeks before outplanting at four reforestation sites. Inoculation with five of the six strains caused significant seedling growth promotion in the greenhouse, which necessitated analysis of relative growth rates (RGR) to evaluate seedling performance in the field. Four months after outplanting, most strains enhanced spruce shoot or root RGRs in the field, but seedling growth responses were strain specific. For example, Pseudomonas strain Ss2-RN significantly increased both shoot and root RGRs by 10-234% at all sites, but increases of 28-70% were most common. In contrast, Bacillus strain S20-R was ineffective at all outplanting sites. In addition, seedlings inoculated with four of th...

Use of strains of Bacillus isolated in China to suppress take-all and rhizoctonia root rot, and promote seedling growth of glasshouse-grown wheat in Australian soils

Several strains of Bacillus subtilis and B. cereus, isolated and selected in China for their ability to promote plant growth and control root disease (yield-increasing bacteria), were tested for their potential to control take-all, caused by Gaeumannomyces graminis var. tritici, and rhizoctonia root rot caused by R. solani AG-8 on wheat seedlings grown in field soils in a glasshouse. Bacillus cereus isolate A47 and B. subtilis B908 consistently reduced the severity of take-all of wheat grown in a sodic acid soil. The amount of disease control was similar to that obtained with the biocontrol isolate Pseudomonas corrugata 2140. B. subtilis B931 was considerably more effective than other bacterial treatments in reducing the severity of rhizoctonia root rot in a calcareous sandy loam soil. Control of rhizoctonia root rot with isolate B931, and also with B. cereus strains A47 and M22 was both substantial and reproducible. Seedling growth promotion effects following bacterial treatment were less consistent than disease control effects. B. subtilis B908 and B. cereus A47-2 and A47-3 gave the most frequent positive growth responses (wheat seedling root weight, shoot weight and shoot length) in the absence of pathogen inoculum. This is the first reported research outside China where these Bacillus isolates have given control of soil-borne root diseases and promoted growth of healthy seedlings under glasshouse conditions.

Microbial Inoculants for Sustainable Forests

Fungal root pathogens are widespread and may cause substantial seedling losses in conifer nurseries. Furthermore, poor seedling survival and growth on reforestation sites results in reduced forest regeneration. Use of microbial inoculants for disease control and plant growth promotion has become an important endeavour. A microbial culture collection of 500 strains was assessed for biological control of fungal root pathogens and/or plant growth promotion of conifer seedlings. Seven of these strains showed significant suppres-sive effects on various soil-bome fungal pathogens. On Douglas fir, two strains, RAL3 and 64-3, reduced disease caused by Fusariumby. 7-42% in repeated growth room assays. The same strains significantly increased healthy stand of white spruce seedlings inoculated with Fusariumand Pythiumin a conifer nursery, and increased the survival of bare-root white spruce seedlings planted on a reforestation site by 19-23%. Both strains also significantly increased new root and total plant dry weights. Strain RAL3 in commercial formulation maintained a viable population of about log 8-9 cfu/ml for over a year when stored at 5°C. Strain survival on seed varied with conifer species. No decreases in bacterial populations were observed on seeds of jack pine or Douglas fir after 37 to 44 days storage at 5°C, but decreases were observed on seeds of white spruce and Scots pine. This study has provided candidate beneficial microbial inocu-lants which offer promise for development of commercial inoculants for the forestry industry.

70 Growth promotion of rice seedlings by TNZ 303

70 Growth promotion of rice seedlings by TNZ 303

An assessment of spruce growth response specificity after inoculation with coexistent rhizosphere bacteria

The influence of inoculation with rhizosphere bacteria on hybrid spruce (Picea glauca × engelmannii) seedling growth was investigated by isolating bacteria from the rhizosphere of naturally regenerating spruce seedlings collected from two ecologically distinct zones of British Columbia. Forty bacterial strains from spruce were screened in a seedling growth experiment, and several strains were shown to stimulate spruce seedling growth. The three most effective spruce growth promoting strains from each ecological zone were then tested in a seedling growth response specificity experiment in which seed, soil, and bacteria from both spruce ecosystems were examined in all possible treatment combinations, including pasteurized soil. Spruce seedling growth was primarily affected by seed and soil source (Salmon Arm &gt; Mackenzie for both factors), and by soil pasteurization (pasteurized &gt; unpasteurized). Significant growth effects due to bacterial treatment in the specificity experiment occurred only in pasteurized soil, but seedling biomass accumulation was stimulated by up to 59% in response to inoculation. There was no evidence of growth response specificity that was related to plant – bacteria adaptation within spruce ecotypes; two of the Mackenzie bacterial strains significantly inhibited growth of Mackenzie seedlings in Mackenzie soil, but two strains stimulated the growth of Salmon Arm seedlings, one in each soil type. Two Salmon Arm strains significantly stimulated growth of Mackenzie seedlings on Salmon Arm soil, and two strains stimulated the growth of Salmon Arm seedlings, one in each soil type. Seedling biomass was greater when treatments of spruce seed, soil, and rhizosphere bacteria that originated from the same geographic site were pooled and compared with treatments in which at least one factor originated from the other site. However, this effect was explained by the significant seed × soil interaction in the absence of bacteria; mean seedling biomass was greatest when spruce seed and soil treatments with the same geographic origin were pooled and compared with unrelated seed – soil combinations. Seedlings from pooled treatments were also significantly larger when bacteria and soil had a common geographic origin, but only when tested in pasteurized soil. Our results indicate that spruce growth promoting rhizosphere bacteria can be isolated from naturally regenerating spruce seedlings, but growth response variability was observed between trials. Seedling growth promotion by bacterial strains was not related to the use of spruce ecotypes, soil, and (or) rhizosphere bacteria with a common geographic origin. Key words: spruce seedlings, growth, inoculation, rhizosphere bacteria.

Influence of soil biota on Douglas-fir (Pseudotsuga menziesii) seedling growth: the role of rhizosphere bacteria

The influence of soil biota on Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) seedling growth was investigated by sowing seed collected from two ecologically distinct zones in British Columbia, Chilliwack and Williams Lake, in soil collected from the same two areas. Seedling biomass of both Douglas-fir ecotypes was greatest in unpasteurized soil collected from the same area as was the seed, but pasteurization negated this effect. In addition, Chilliwack seedlings responded specifically to biota present only in Chilliwack soil. To determine if rhizosphere bacteria were involved in these growth responses, bacteria were isolated from the rhizosphere of wild Douglas-fir seedlings collected from both locations, and putative growth promoting bacteria were selected in a screening experiment. Selected bacteria were then tested for seedling growth response specificity using a factorial design in which seed, soil, and bacteria from both locations were evaluated in all combinations. Inoculation of Douglas-fir seed with some of the selected bacterial isolates increased seedling biomass in pasteurized soil to a level similar to that of seedlings grown in unpasteurized soil, but there was no evidence that adaptive relationships involving bacteria, Douglas-fir, and the soil in which they naturally grew were important in effecting seedling growth promotion. However, Douglas-fir shoot biomass increased 39% and root biomass 68% after bacterial inoculation in some treatment combinations involving pasteurized soil. Key words: Douglas-fir seedlings, growth, rhizosphere bacteria.

Rhizosphere colonization and seedling growth promotion of lodgepole pine by Bacillus polymyxa

Lodgepole pine seed was inoculated with Bacillus polymyxa isolate L6-16R, a strain marked with antibiotic resistance to 100 mg rifamycin per litre. Inoculation resulted in statistically significant seedling biomass increases after 8 weeks of pine growth. The L6-16R rhizosphere population declined by an order of magnitude per month, from ca. 106 cfu/g dry weight of pine root tissue 4 weeks past inoculation to ca. 104 cfu/g of root tissue 12 weeks past inoculation. Seed-lings from three of four pine provenances had mean shoot and root dry weight increases of up to 35% due to seed inoculation, but shoot growth of the fourth provenance was inhibited. The size of the L6-16R rhizosphere population was not correlated to the magnitude of the shoot growth response 4 weeks after inoculation, but it showed a strong correlation with shoot growth 8 weeks after inoculation. These results indicate that the promotion of pine seedling growth may be a function of the size of the bacterial rhizosphere population that develops 4 weeks after inoculation, and that B. polymyxa may promote growth of lodgepole pine collected from many, but not all provenances. Key words: Bacillus polymyxa, lodgepole pine, growth promotion, rhizosphere colonization.

Promotion of Germination and Early Seedling Growth of Zoysia japonica Steud. Seeds through Encapsulation

Promotion of Germination and Early Seedling Growth of <I>Zoysia japonica</I> Steud. Seeds through Encapsulation