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1.
Few studies of the inoculation of cereal crops with N2-fixing bacteria have included more than one or two plant genotypes. In a recent study performed in Argentina using 12 different maize genotypes, it was found in 2 consecutive field experiments that several of them responded consistently, either negatively or positively, to inoculation with a mixture of strains of Azospirillum spp. The present study in post was performed to investigate the effect of inoculation of individual strains (and a mixture) of Azospirillum spp., and their nitrate reductase negative (NR-) mutants, on the growth of four of these maize genotypes. Two of these genotypes were grown in 15N-labelled soil with the aim of quantifying any contributions of biological N2 fixation. Two genotypes (Morgan 318 and Dekalb 4D-70) produced similar increases in grain yield when they were inoculated with a mixture of Azospirillum spp. strains or fertilized with the equivalent of 100 kg N ha-1. The other genotypes (Dekalb 2F-11 and CMS 22) showed little response to inoculation or N fertilization. The Morgan 318 and Dekalb 4D-70 genotypes showed a large increase in total N accumulation, suggesting that the response was due to increased N acquisition, but not due to bacterial nitrate reductase as the NR- mutants generally caused plant responses similar to those of the parent strains. Despite problems with the stabilization of the 15N enrichment in the soil, the 15N isotope dilution results indicated that there were very significant biological nitrogen fixation (BNF) contributions to the Dekalb 4D-70 and CMS 22 maize genotypes.Dedicated to Professor J.C.G. Ottow on the occasion of his 60th birthday  相似文献   

2.
Summary Three field experiments with wheat were conducted in 1983, 1984, and 1985 in Terra Roxa soil in Paraná, the major Brazilian wheat-growing region, to study inoculation effects of various strains of Azospirillum brasilense and A. amazonense. In all three experiments inoculation with A. brasilense Sp 245 isolated from surface-sterilized wheat roots in Paraná produced the highest plant dry weights and highest N% in plant tops and grain. Grain yield increases with this strain were up to 31 % but were not significant. The application of 60 or 100 kg N ha–1 to the controls increased N accumulation and produced yields less than inoculation with this strain. Another A. brasilense strain from surface-sterilized wheat roots (Sp 107st) also produced increased N assimilation at the lower N fertilizer level but reduced dry weights at the high N level, while strain Sp 7 + Cd reduced dry weights and N% in the straw at both N levels. The A. amazonense strain isolated from washed roots and a nitrate reductase negative mutant of strain Sp 245 were ineffective. Strains Sp 245 and Sp 107st showed the best establishment within roots while strain Cd established only in the soil.  相似文献   

3.
The specificity of the infection of maize, wheat and rice roots by N2-fixing Azospirillum spp was studied in four greenhouse experiments using pots with unsterilized soil and in two field experiments. In all experiments A. lipoferum was most frequently isolated from externally sterilized roots of maize, and A. brasilense nir? (nitrite reductase negative) from wheat and rice. In pot experiments, A. brasilense nir+ was isolated with moderate frequency from within maize roots but rarely from within wheat or rice roots. Inoculation of the pots with a mixture of representative strains of the three Azospirillum groups had no effect on the proportion of strains recovered from each plant species. In the field experiments, inoculation with spontaneous streptomycin-resistant mutants of two of the representative strains confirmed the apparent specificity of A. lipoferum for maize roots and of A. brasilense for wheat but the results were partially obscured by the unexpectedly high proportion of streptomycin-resistant strains isolated from within the roots of uninoculated plants.  相似文献   

4.
Summary The nitrogen metabolism of wheat plants inoculated with various Azospirillum brasilense strains and nitrate reductase negative (NR–) mutants was studied in two monoxenic test tube experiments. The spontaneous mutants selected with chlorate under anaerobic conditions with nitrite as terminal electron acceptor fixed N2 in the presence of 10 mM NO3 – and were stable after the plant passage. One strain (Sp 245) isolated from surface-sterilized wheat roots produced significant increases in plant weight at both NO3 levels (1 and 10 mM) which were not observed with the NR– mutants or with the two other strains. Similar effects were observed in a pot experiment with soil on dry weight and total N incorporation but only at the higher N fertilizer level. In the monoxenic test tube experiments plants inoculated with the mutants showed lower nitrogenase activities than NR+ strains at the low NO3 – level (1 = mM) but maintained the same level of activity with 10 mM NO3 – where the activity of all NR+ strains was completely repressed. The nitrate reductase activity of roots increased with the inoculation of the homologous strains and with the mutants at both NO3 – levels. At the low NO3 – level this also resulted in increased activity in the shoots, but at the high NO3 – level the two homologous strains produced significantly lower nitrate reductase activity in shoots while the mutants more than doubled it. The possible role of the bacterial nitrate reductase in NO3 – assimilation by the wheat plant is discussed.  相似文献   

5.
Summary The response of the cotton plant to inoculation with six strains of Azospirillum brasilense was investigated under subtropical conditions in Egypt. Azospirilla populations and activities were increased as a result of root inoculation with liquid inoculum of Azospirillum sp. Highest C2H2 — reduction activities on roots were obtained with strains S631 and Sp Br 14 (means of 216.85 and 209.50 nmol C2H4g–1 root h–1 respectively) while strain M4 gave the lowest activity (mean of 100.8 nmol C2H4g–1 root h–1). Statistical analysis showed that Azospirillum strains 5631, Sp Br 14, E15 and SC22 significantly increased the plant dry weight and nitrogen uptake while inoculation with strains M4 and SE had no significant effect in that respect.  相似文献   

6.
The Azospirillum 10SW used in our experiments was isolated from roots of wheat growing in nitrogen-poor soil of a hilly region of Nepal, where inorganic nitrogen fertilizers were never used. The main objectives of this work were to assess the effects of inorganic nitrogen fertilization in the yield responses of wheat grown in association with the bacteria. The in vitro experiments were done in laboratory, whereas the pot experiments were performed in a greenhouse. The nitrogenase activities of in vitro grown Azospirillum were repressed by nitrate. The magnitude of repression was lower when the bacteria were growing in association with wheat. The number of roots per plant was increased significantly in inoculated plants irrespective of the nitrate concentration of the medium. Inoculation with Azospirillum 10SW also increased the yield of wheat grown in pots with medium levels of nitrogen fertilization. These data show the possibility of inoculation of this Azospirillum spp. in combination with nitrogen fertilizer to improve the yield of wheat. Azospirillum inoculation enhanced the development of roots and shoots in the early growth stages of wheat. It may be one of the factors responsible for the yield increases. Received: 11 December 1996  相似文献   

7.
Plant growth-promoting rhizobacteria, particularly those from the genus Azospirillum spp., may affect root functions such as growth and nutrient/water uptake, which in turn may affect shoot growth. Calculations based on data from literature on shoot and root mass of crop grasses (79 plant/bacteria associations were analyzed) revealed that inoculation with Azospirillum spp. increased the shoot-to-root (S/R) ratio in about half of reported cases and decreased the S/R ratio in the other half. In 11 of 35 cases, the S/R ratio increased when the shoot mass increased more than the root mass. In 23 of 35 cases, the root mass did not increase, yet the S/R ratio still increased. Thus, the increase in the S/R ratio indicated that shoot growth responds to inoculation more than root growth. A decrease in the S/R ratio occurred when (a) root growth dominated shoot growth even though both increased (16 of 36 cases), or (b) root growth either increased or remained unchanged, and shoot growth was either unaffected or even decreased (19 of 36 cases). This analysis suggests that: (a) Azospirillum spp. participates in the partitioning of dry matter (both carbon compounds and minerals) at the whole plant level by affecting root functions, and (b) the bacteria affect crop grass through multiple mechanisms operating during plant development.  相似文献   

8.
Plant-growth promoting rhizobacteria (PGPR) play an important role in plant health and soil fertility. The experiment was conducted as factorial experiment with two factors of Azospirillum and Azotobacter. The bacterial strains were Azospirillum lipoferum s-21, A. brasilense DSM 1690, A. lipoferum DSM 1691, Azotobacter chroococcum s-5, and A. chroococcum DSM 2286. The results indicated that growth promotion by PGPR appears from early stages of growth, 45 days after inoculation (DAI). Beneficial effects of bacterial inoculation on ear growth were observed after 75 DAI. Inoculation with PGPR increased dry weights of leaf, stem, and grain and hence total biomass sampled at 90, 105, and 120 (harvest time) DAI. The greatest grain weight was produced by Azospirillum s-21 inoculation. Dual inoculation with Azotobacter s-5 + Azospirillum s-21 significantly increased total dry weight up to 115%. Results of this study showed that leaf area index and crop growth index were significantly affected by bacterial treatments.  相似文献   

9.
华北地区采用无机氮测试和植株速测进行夏玉米氮肥推荐   总被引：2，自引：0，他引：2  
A field experiment with a split-plot design was carried out at Dongbeiwang Farm in Beijing Municipality to establish reliable N fertilizer recommendation indices for summer maize (Zea mays L.) in northern China using the soil Nmin(mineral N) test as well as the plant nitrate and SPAD (portable chlorophyll meter readings) tests. The results showed that Nrnin sollwert (NS) 60 kg N ha^-1 at the third leaf stage and N rate of 40 to 120 kg N ha^-1 at the tenth leaf stage could meet the N requirement of summer maize with a target yield of 5.5-6 t ha^-1. Sap nitrate concentrations and SPAD chlorophyll meter readings in the latest expanded maize leaves at the tenth leaf stage were positively correlated with NS levels, indicating that plant nitrate and SPAD tests reflected the N nutritional status of maize well. Considering that winter wheat subsequently utilized N after the summer maize harvest, the 0-90 cm soil Nmin (74 kg N ha^-1) and apparent N loss (12 kg N ha^-1) in the NS60＋40 treatment were controlled at environmentally acceptable levels. Therefore NS60＋40, giving a total N supply of 100 kg N ha^-1, was considered the optimal N fertilizer input for summer maize under these experimental conditions.  相似文献   

10.
Recent field inoculation trials with Azospirillum and Azotobacter spp. applied to cereal and forage crops have shown extremely different results in yield response. Some aspects of bacteria-plant interactions affecting yield response are discussed. These include provision of fixed nitrogen, specificity and adaptation to root habitat, influence of microbial metabolites, enhancement of VA-mycorrhiza, displacement of deleterious rhizosphere microorganisms, differences between host plant genotypes, competitive ability and longevity of inoculants. Based on these considerations, needs for further research will be outlined.  相似文献   

11.
A plant growth-promoting rhizobacterium (Azospirillum brasilense Sp7) and a bio-control fungus, which can solubilize insoluble phosphorus (Trichoderma harzianum Rifai 1295-22), were evaluated for their single and combined effects on dry bean (Phaseolus vulgaris) and wheat (Triticum aestivum L.) grown in soil. A pot experiment with bean and a field experiment with both bean and wheat were established. In contrast to single inoculation of Trichoderma, the single inoculation of Azospirillum and the double inoculation did not significantly (P >0.05) increase nodule numbers and nodule mass at 45 days after planting in pot grown beans. However, the Azospirillum inoculation with supplementary phosphorus significantly (P <0.05) increased nodule mass. There were no significant (P >0.05) differences among the inoculation treatments for plant dry weight, total plant nitrogen, and total plant phosphorus at 45 days after planting in both pot and field experiments with bean. However, the combined inoculation and rock phosphate application at 1 Mg ha–1 significantly (P <0.05) increased bean seed yield, total seed nitrogen and phosphorus in the bean field trial. This treatment more than doubled the mentioned properties compared to the control. The microbial inoculations, with the exception of the combined inoculation, significantly (P <0.05) increased total seed nitrogen, but never affected seed yield in the wheat field trial (P >0.05). The combined inoculation improves many plant and yield parameters and, therefore, has some advantages over single inoculation provided that rock phosphate was supplied at an amount not exceeding 1 Mg ha–1. Higher rock phosphate application rates decreased many plant and yield parameters in our study.This work was carried out at Gaziosmanpaa University, Tokat, Turkey.  相似文献   

12.
Summary At least 105–106 viable cells of the rhizopseudomonad strain 7NSK2* had to be applied per seed of maize cultivar Beaupré and barley cultivar Iban in order to obtain a beneficial effect on plant growth under greenhouse conditions. In pot experiments where an increase in plant growth, varying between 15% and 25%, was observed, the introduced strain 7NSK2* constituted at least 20% of the bacterial root colonizers. This colonization provoked a shift in the fungal rhizospheric community. Due to the inoculation with 7NSK2, Penicillium spp. became the dominant isolates, while Trichoderma spp. were the dominant isolates in pot experiments with low and inefficient inoculum levels of 7NSK2*.  相似文献   

13.
Summary We studied the dominant diazotrophs associated with maize roots and rhizosphere soil originating from three different locations in France. An aseptically grown maize plantlet, the spermosphere model, was used to isolate N2-fixing (acetylene-reducing) bacteria. Bacillus circulans was the dominant N2-fixing bacterium in the rhizosphere of maize-growing soils from Ramonville and Trogny, but was not found in maize-growing sandy soil from Pissos. In the latter soil, Enterobacter cloacae, Klebsiella terrigena, and Pseudomonas sp. were the most abundant diazotrophs. Azospirillum sp., which has been frequently reported as an important diazotroph accociated with the maize rhizosphere, was not isolated from any of these soils. The strains were compared for their acetylene-reducing activity in the spermosphere model. The Bacillus circulans strains, which were more frequently isolated, also exhibited significantly greater acetylene-reducing activity (3100 nmol ethylene day-1 plant-1) than the Enterobacteriaceae strains (180 nmol ethylene day-1 plant-1). This work indicates for the first time that Bacillus circulans is an important maizerhizosphere-associated bacterium and a potential plant growth-promoting rhizobacterium.  相似文献   

14.
Summary Bacteria of the genus Azospirillum are extensively studied for their plant-growth promoting effect following inoculation. Physiological and biochemical studies of these diazotrophic bacteria are now benefiting from recent breakthroughs in the development of genetic tools for Azospirilum. Moreover, the identification and cloning of Azospirillum genes involved in N2 fixation, plant interaction, and phytohormone production have given new life to many research projects on Azospirillum. The finding that Azospirillum genes can complement specific mutations in other intensively studied rhizosphere bacteria like Rhizobia will certainly trigger the exploration of new areas in rhizosphere biology. Therefore a review of the Azospirillum-plant interactions is particularly timely.  相似文献   

15.
Summary Mature (flowering) tobacco (Nicotiana tabacum cv. PBD6, Nicotiana rustica cv. Brasilia) and maize (Zea mays cv. INRA 260) plants were grown in an acid sandy-clay soil, enriched to 5.4 mg Cd kg–1 dry weight soil with cadmium nitrate. The plants were grown in containers in the open air. No visible symptoms of Cd toxicity developed on plant shoots over the 2-month growing period. Dry-matter yields showed that while the Nicotiana spp. were unaffected by the Cd application the yield of Z. mays decreased by 21%. Cd accumulation and distribution in leaves, stems and roots were examined. In the control treatment (0.44 mg Cd kg–1 dry weight soil), plant Cd levels ranged from 0.4 to 6.8 mg kg–1 dry weight depending on plant species and plant parts. Soil Cd enrichment invariably increased the Cd concentrations in plant parts, which varied from 10.1 to 164 mg kg–1 dry weight. The maximum Cd concentrations occurred in the leaves of N. tabacum. In N. rustica 75% of the total Cd taken up by the plant was transported to the leaves, and 81% for N. tabacum irrespective of the Cd level in the soil. In contrast, the Cd concentrations in maize roots were almost five times higher than those in the leaves. More than 50% of the total Cd taken up by maize was retained in the roots at both soil Cd levels. The Cd level in N. tabacum leaves was 1.5 and 2 times higher at the low and high Cd soil level, respectively, than that in N. rustica leaves, but no significant difference was found in root Cd concentrations between the two Nicotiana spp.Cd bioavailability was calculated as the ratio of the Cd level in the control plants to that in the soil or as the ratio of the additional Cd taken up from cadmium nitrate to the amount of Cd applied. The results showed that the plant species used can be ranked in a decreasing order as follows: N. tabacum > N. rustica > Z. mays.  相似文献   

16.
Interactions between the N2-fixing bacterium Azospirillum brasilense and the mycorrhizal fungus Glomus mosseae were studied in relation to their effects on the growth and nutrition of Zea mays (C4) and Lolium perenne (C3) plants. Although roots from plants inoculated with Azospirillum exhibited C2H2 reduction activity no significant effect of inoculation on N concentration in the plant shoots was found. With non-mycorrhizal plants, inoculation with Azospirillum resulted in increased dry matter production at the first harvest compared to the effect achieved by supplying N as fertilizer, but this trend was reversed at the last harvest. However, with mycorrhizal maize plants, Azospirillum, which stimulated the development of VA mycorrhiza, was still effective in improving plant growth and nutrient uptake at the last harvest. Azospirillum and N behaved similarly in enhancing the growth and nutrition of mycorrhizal maize. The dual inoculation of maize by Azospirillum and Glomus produced plants of a similar size, N content, and a higher P content, than those supplied with N and P.  相似文献   

17.
Summary Microscopic observations of the root system of pearl millet (Pennisetum americanum (L.) Leeke) var. BJ 104 after surface sterilization and incubation in phosphate malate triphenyl tetrazolium chloride (TTC) revealed extensive colonization by Azospirillum spp. when plants were grown in sterile, partially sterile and field conditions as evidenced by the TTC-reducing property of active cells of the bacterium. Quantitative studies showed the need to standardize the techniques further to ensure more precise monitoring of the bacteria in the rhizosphere, as large numbers of soil bacteria were found capable of growth on specific media, thus interfering with the plate counts. Seed inoculation with A. brasilense increased the mean grain yield of pearl millet under different agroclimatic conditions in India. The mean increase in grain yield due to inoculation over uninoculated controls was also noticed with graded levels of fertilizer nitrogen (urea). Inoculation alone contributed to increased nitrogen uptake of plants with varying levels of fertilizer nitrogen application under sandy loam soil conditions (pH 7.3). The effects of inoculation were more prominent under lower levels of nitrogen than at the higher levels. The root biomass under field conditions was increased with Azospirillum spp. inoculation at 10 and 20 kg N/ha than their corresponding uninoculated controls.  相似文献   

18.
 Thirty-five Azospirillum strains (13 strains from plant roots and 22 strains from soils) were isolated from Ishigaki island, Japan, which has a subtropical climate. These strains were different from each other according to polymerase-chain-reaction band patterns obtained by using a random primer (OPT-08). Two Azospirillum strains (AZ43 and AZ92-2) were also examined for use in further experiments. Inoculation of lowland rice with these strains enhanced early growth of rice to various degrees. Inoculation of strains VIII.P1-2, AZ92-2, V.S2-2, and V.P5 in sterilized soil yielded higher shoot dry weights than the application of 90 μg N g–1 soil without inoculation. Only inoculation with strains AZ92-2 and VIII.P1-2 caused higher N uptake than the application of 90 μg N g–1 soil. Three strains were selected for the next experiment based on the results of their effect on the early growth of rice. An investigation was conducted to determine the ability of two indigenous Azospirillum strains (V.S2-2 and VIII.P1-2) and one stock strain (AZ92-2) to promote growth and nutrient-uptake of lowland rice in unsterilized soil under several levels of N application (0, 80, 160, and 240 mg N pot–1). Inoculation with these strains without N application increased shoot dry weight by 12–15% compared to the uninoculated treatment. Inoculation with Azospirillum V.S2-2 together with the application of 160 mg N pot–1 resulted in a shoot dry weight as high as that obtained in the treatment with 240 mg N pot–1 without inoculation. Thus, in this former case, the amount of N applied could be reduced by 80 mg pot–1 due to the effect of the microbial inoculum without a significant change in the high, targeted, yield.  相似文献   

19.
Abstract

To investigate the effect of biofertilizers on the growth and yield of Eucalyptus grandis seedlings, greenhouse experiments were performed applying fertilizers based on agricultural byproducts, inoculated with nitrogen-fixing bacteria of the genera Azotobacter spp and Azospirillum spp. For the biofertilizers formulation, a nitrogen-fixing bacteria consortium was inoculated, and the experimental design was a 2?×?2 × 2 factorial arrangement, the factors were nitrogen source (NS: chicken manure), source of carbon (CS: eucalyptus leaf litter) and source of micronutrients (RS: rhizospheric soil) with two dose levels, inoculated with a consortium of Azotobacter spp and Azospirillum spp. The optimal time production of the best biofertilizers was 30?days, with the highest density of Azospirillum (9.23 × 106 CFU·g?1) and Azotobacter (19.3 × 106 CFU·g?1), and total nitrogen contents in the range of 2.15-5.64%, released into the biofertilizers with chicken manure and bioaugmented with the bacterium consortium. The treatment with the highest dose of biofertilizer, 500?g, showed the most significant effect on seedling development, increasing growth, stimulating rooting and the highest increase in leaf number. The results show that biofertilizers contributed to Eucalyptus grandis crop yield, and biofertilizers are proposed as an alternative for implementing sustainable soil management in the forest sector.  相似文献   

20.
The nitrogen-fixing capacity of a range of commercial cultivars of maize (Zea mays L.) was evaluated by the 15N isotope-dilution method. Biological nitrogen fixation (BNF) expressed as percent nitrogen derived from air (Ndfa) ranged from 12 to 33 regardless of nitrogen fertilization. BNF was not affected by mineral nitrogen fertilization except on cultivar Topacio and PAU-871 cultivars. Subsequently, culturable bacterial diazotrophs were isolated from endophytic tissue of maize: seed, root, stem, and leaf. All isolates were able to grow on N-free semisolid medium. Eleven bacteria isolates showed nitrogen-fixing capacity by the reduction of acetylene to ethylene and confirmed by PCR the presence of nifH gene in their genome. Identification of the 11 isolates was performed by bacteriological methods, 16S rRNA gene sequences, and phylogenetic analysis, which indicated that the bacteria isolated were closely related to Pantoea, Pseudomonas, Rhanella, Herbaspirillum, Azospirillum, Rhizobium (Agrobacterium), and Brevundimonas. This study demonstrated that maize cultivars obtain significant nitrogen from BNF, varying by maize cultivar and nitrogen fertilization level. The endophytic diazotrophic bacteria isolated from root, stem, and leaf tissues of maize cultivars may contribute to BNF in these plants.  相似文献   

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