Diversity of <Emphasis Type="Italic">Trifolium ambiguum</Emphasis>—nodulating rhizobia from the lower Caucasus

Kura clover (Trifolium ambiguum M.B.) is a perennial rhizomatous forage legume whose use is currently limited by difficulties in its establishment in part attributable to nodulation problems and very specific rhizobial requirements. A limited number of Kura clover-nodulating rhizobial strains are currently available and many have a limited effectiveness. In this study, 128 rhizobia were isolated from four sites in the center of origin of Kura clover (i.e., two in Azerbaijan, one in Armenia, and one in Northwest Iran) using the three ploidy levels of Kura clover (diploid, tetraploid, and hexaploid), red clover (Trifolium pratense L.), and white clover (Trifolium repens L.) plants as trap hosts. Rhizobia were fingerprinted using repetitive extragenic palindromic polymerase chain reaction (BOXA1R primer) and their genetic diversity was measured using the Shannon-Weaver diversity index. The nodulation specificity and phenotypic diversity of a subset of 13 isolates was determined. Genetic diversity among the 128 isolates was large and similar for rhizobia grouped according to their geographic origin or original host plant. Phenotypic diversity was significant; percentage of similarity among 13 isolates ranging between 38 and 92%. Nodulation specificity of the Kura clover-nodulating rhizobial isolates studied was less complex and not as clearly delineated as previously reported. Some strains originally isolated from Kura clover could effectively nodulate more than one ploidy level of Kura clover and even one or both of two other Trifolium species (i.e., red clover and white clover). Three strains formed effective nodules on both Kura clover and white clover; however, none promoted plant growth of both species to levels currently obtained with commercial inoculants when evaluated in a growth chamber. Rhizobial isolates that are highly effective with both species have yet to be identified.     

Yield and N assimilation of winter wheat (Triticum aestivum L., var. Norstar) inoculated with rhizobacteria

The effects of bacterial inoculants on the growth of winter wheat were studied in a growth chamber. Azospirillum brasilense, Azotobacter chroococcum, Bacillus polymyxa, Enterobacter cloacae, or a mixture of the four rhizobacteria were the inoculants tested. Inoculation effects on yield, yield components, and N-derived from fertilizer (Ndff) were assessed. The response of plants inoculated with individual bacteria was inconsistent and varied with treatment. At the first harvest (58 days after planting-DAP) plants inoculated with the mixture exhibited increases in plant dry weight, total-N and Ndff. At the second harvest (105 DAP), plants inoculated with A. brasilense and the mixture exhibited increases in shoot biomass, whereas at maturity (170 DAP), the inoculated plants showed no differences in total-N or shoot dry matter yield, as compared to the uninoculated controls. Inoculation with A. brasilense, however, increased the Ndff in the shoots, and B. polymyxa tended to enhance grain yield. Practical use of these rhizobacteria as inoculants for winter wheat may have limited value until such time as we better understand factors which influence rhizosphere competence of bacterial inoculants.     

Effect of strains of Rhizobium trifolii on the establishment of oversown white clover (Trifolium repens)

Strains of Rhizobium trifolii incorporated into commercial peat inoculants were compared for their effect on the establishment and growth of oversown white clover (Trifolium repens) on soils devoid of infective rhizobia.There were marked differences in numbers of seedlings establishing and clover dry matter production per hectare with the various strains. However, when adjusted to a constant number of established seedlings, dry matter production from all strains, apart from one strain at one site, were similar indicating that the strains did not appear to influence the growth of individual clover plants.The marked differences in establishment of clover inoculated with the various strains could not be accounted for by differences in the number of rhizobia in the peat inoculant.Selecting strains of rhizobia for ability to increase establishment is considered important where clover is oversown onto soils devoid of rhizobia.     

Performance of Kura clover compared to that of perennial forage legumes traditionally cultivated in central Europe

Kura clover (Trifolium ambiguum M. Bieb.) is a rhizomatous perennial legume that is native to Caucasia, is extremely persistent in North America, but its performance has not been adequately evaluated in Europe. The objective of this research was to compare forage yield and nutritive value of Kura clover to lucerne (Medicago sativa L.), red clover (Trifolium pretense L.) and white clover (Trifolium repens L.) at two locations in Poland. All clover stands thinned markedly by spring of the second production year because of infection by Sclerotinia crown and stem rot, but lucerne stands remained dense and this legume produced the highest total yield over 3 or 4 production years. Kura clover yields of 7.2–8.3?Mg?ha^?1 were second to lucerne by the third production year but long-term performance was diminished by stand thinning. Kura clover and white clover had lower fiber concentrations and greater protein concentrations and forage digestibility than red clover and lucerne. Kura clover can be a source of high-quality forage in Europe, but cannot be recommended for use in areas with known Sclerotinia trifoliorum presence until resistance to this pathogen is developed.     

Effectiveness of two arbuscular mycorrhizal fungi on concentrations of essential oil and artemisinin in three accessions of Artemisia annua L.

A field experiment was conducted to study and compare the effectiveness of two arbuscular mycorrhizal fungi (AMF), Glomus macrocarpum (GM) and Glomus fasciculatum (GF) on three accessions of Artemisia annua. The AM inoculation significantly increased the production of herbage, dry weight of shoot, nutrient status (P, Zn and Fe) of shoot, concentration of essential oil and artemisinin in leaves as compared to non-inoculated plants. The extent of growth, nutrient concentration and production of secondary plant metabolites varied with the fungus–plant accession combination. The mycorrhizal dependency of the three accessions was related to the shoot: root ratio. Comparing the two fungal inoculants in regard to increase in essential oil concentration in shoot, the effectiveness of GF was more than that of GM. While in two accessions, GM was more effective in enhancing artemisinin concentration than GF. Increase in concentration of essential oil was found to be positively correlated to P-status of the plant. Conversely, no correlation was found between shoot-P and artemisinin concentration.     

Growth effects of microorganisms based commercial products inoculated to tissue cultured banana cultivated in three different soils in Kenya

The effect of inoculation of microorganisms-based commercial products on post-flask management and field establishment of tissue cultured (TC) banana plantlets was investigated. TC banana cv. Gros Michel plantlets were inoculated with Bacillus, mycorrhizal and Trichoderma based products in a Vertisol, Humic Nitisol, Rhodic Ferralsol and conventional nursery media. Initial inoculation of plants with products was done at the acclimatization phase and subsequently at the potting phase. Survival of inoculated plantlets was recorded at the end of the acclimatization phase, 8 weeks after deflasking. Effect of products on growth was evaluated as ability to enhance height and girth of pseudostem, leaf length, leaf width, number of functional leaves and root and shoot biomass yield. The efficacy of products on survival of plants at hardening was variable and dependent on soil type. Inoculation with Bacillus enhanced survival of plants in the Vertisol, mycorrhiza and Trichoderma inoculation in the Rhodic Ferralsol and mycorrhiza in the Humic Nitisol and conventional media. Performance of inoculated plants was dependent on soil type. Application of Bacillus based products significantly increased plant growth (leaf length, leaf width, plant height, shoot dry weights) in the Vertisol and Rhodic Ferralsol in the nursery phase. Application of multiple species mycorrhiza and Trichoderma under field conditions significantly increased plant growth (apparent volume and leaf surface area) in the Vertisol by over 100% and 25% compared to the control and conventional practice respectively. Mycorrhizal colonization was not significantly affected by product inoculation. However, higher percentages of colonization were observed with Bacillus inoculation in the Vertisol and by mycorrhizae and Trichoderma in the Rhodic Ferralsol compared to the non-inoculated controls. Results demonstrate that tissue cultured bananas can benefit from application of arbuscular mycorrhizal fungi, Trichoderma and Bacillus to improve survival and growth during the nursery phase as well as enhance plant performance under field conditions. The effect of microorganisms-based commercial inoculants is however dependent on soil type and the stage of plant development.     

Kura Clover Response to Potassium Fertilization

Kura clover (Trifolium ambiguum M.B.) is a persistent perennial forage legume that produces high-quality herbage for grazing, but its response to potassium (K), an essential plant nutrient, is unknown. Our objective was to determine the effect of four dipotassium oxide (K₂O) rates on forage yields and stands of Kura clover compared to birdsfoot trefoil (Lotus corniculatus L.) and alfalfa (Medicago sativa L.). There was a significant linear response in Kura clover and alfalfa forage yields to K₂O fertilization each year. Averaged over 4 years, Kura clover forage yield increased by 0.024 Mg ha^–1 per kg of K₂O applied, and the yield response was similar for alfalfa. Birdsfoot trefoil forage yield response to K₂O fertilization was less than those of alfalfa and Kura clover. In the first 2 years after seeding, Kura clover forage yields were consistently less than for alfalfa at all rates of K₂O fertilizer, but in subsequent years Kura clover yields were similar to or exceeded those of alfalfa. Final groundcover values, an estimate of stand density, of unfertilized (0 K₂O rate) Kura clover, birdsfoot trefoil, and alfalfa were 86, 35, and 21%, respectively. Final groundcover of Kura clover and alfalfa was increased by K₂O fertilization. We conclude that Kura clover has good persistence with low soil K fertility but stands and yields can be increased by fertilization.     

复合接种剂对三叶草生长特性和品质的影响

利用从兰州地区红三叶 (Trifolium pratense L.) 和白三叶（Trifolium repens L.）根际分离、 筛选获得的4株植物根际促生细菌（代号:A-Hsg、 B-ls1 3、 C-lhs11、 D-lhs14) 制作微生物接种剂,采用盆栽法测定不同接种剂处理对红三叶草生长特性及品质的影响。结果表明,本研究制作的接种剂符合《农用微生物菌剂》质量标准（GB 20287-2006）。复合接种剂处理AD对红三叶草株高、 根长促进作用显著 (P0.05),分别较对照增加33.62%和46.20%。AB和AD处理红三叶草地上植物量增重显著,较对照增加了101.69%和94.98%。BC和AD处理对地下植物量增加显著,增加了197.63%和151.18%。AC、 AD和BCD处理后红三叶草整株磷含量均高于对照,其中BCD处理较对照差异显著（P0.01）,磷含量较对照增加了15.38%。ABCD处理红三叶草整株的含氮量较对照达到了显著水平（P0.05）,较对照增加了14.77%。ABD、 BCD和ABCD处理均可提高红三叶草地上部分粗蛋白含量,其中处理ABCD粗蛋白含量较对照增加最多,增加了14.62%,达到了显著水平（P0.05）。复合接种剂AD、 AB、 BC、 AC、 ABD、 BCD和ABCD接种后,对红三叶草生长特性和品质的提高表现出良好的促进效果,可作为复合菌肥材料作进一步研究。     

Differential responses of forage legumes to aluminum

Response of alfalfa (Medicago sativa L.), birdsfoot trefoil (Lotus corniculatus L.), and red clover (Trifolium pratense L.) to aluminum was evaluated in a nutrient culture system under controlled conditions. In each of the species, varietal differences were also compared. In the absence of Al stress, varieties of alfalfa and Tensas red clover produced more dry weight than the other legumes. However, among the legumes tested, alfalfa was the most sensitive to Al. Aluminum reduced the uptake of many of essential nutrients. Overall, red clover cultivars experienced the least reduction in elemental uptake, whereas alfalfa cultivars experienced the greatest reduction in uptake of elements under Al stress. The efficiency ratio (ER) assisted in differentiating legumes entries into efficient and inefficient utilizers of absorbed nutrients. The ER is defined as milligrams of dry shoot weight produced per milligram of element in the shoot. The presence of Al in the growth medium reduced the ER for all elements. With a few exceptions, ER for various elements, gave positive correlations with shoot weight. The species and cultivars used in this study showed inter‐ and intraspecific differences in growth, uptake of nutrients and nutrient efficiency ratios in the presence or absence of Al stress.     

Peculiar effect of Azospirillum inoculation on growth and nitrogen balance of winter wheat (Triticum aestivum)

Summary Wheat plants (Triticum aestivum) grown in pots and in the field under the Mediterranean climate of the south of France were inoculated with a strain of Azospirillum brasilense. Comparisons with non-inoculated plants grown under the same conditions showed significant responses to inoculation with an increase in the number of fertile tillers, shoot and root dry weight, and root to shoot biomass ratio. The roots of inoculated plants attracted relatively more assimilates than those of the control plants until a late stage of growth (heading stage) but the rhizosphere respiration expressed per unit of root growth was not increased by inoculation. Nitrogen yield, both total and in grains, was also enhanced; however, N percentages of all aerial parts of the plants grown in pots were always statistically lower after inoculation than in the control. At maturity, the N % in seeds was 1.81 and 2.45, respectively. The possible mechanisms of this effect of inoculation under the experimental conditions of this study are discussed.     

丛枝菌根真菌群落对白三叶草植株生物量磷吸收和土壤磷酸单酯酶活性的影响

丛枝菌根真菌（AMF）在土壤与植物的磷素循环中发挥着关键的作用。采用盆栽实验研究了丛枝菌根真菌群落对白三叶草植株生物量、磷吸收和土壤磷酸单酯酶活性的影响。结果表明,接种不同AMF群落均能显著地促进白三叶草植株的生长及其对磷素的吸收,提高根际土壤磷酸单酯酶的活性。Mnp处理中,白三叶草生物量最大,白三叶草总生物量、茎叶生物量和根系生物量分别比对照处理（-M）提高64.48%、61.48%和84.91%。不同菌根处理中,Mck处理显著地提高白三叶草磷吸收和土壤磷酸单酯酶活性,白三叶草磷吸收总量和茎叶磷吸收量分别比对照（-M）提高107.18%和91.91%,土壤碱性磷酸单酯酶和酸性磷酸单酯酶活性相对对照（-M）分别提高54.33%和138.43%。碱性磷酸单酯酶活性与AMF群落中的Acaullospora属孢子数呈显著的正相关关系,而酸性磷酸单酯酶活性则主要受Paraglomus属孢子数的影响。说明接种AMF群落可显著地影响土壤的磷酸单酯酶活性,从而影响白三叶草的生长及其对磷素的吸收。     

白三叶草/根瘤菌共生固氮潜力及干旱限制因素

为了探讨白三叶草生物固氮与土壤水分供应和菌种基因型的关系,采用温室盆栽试验方法,对9个基因型的三叶草根瘤菌固氮效率和与土壤含水量的关系进行了研究。结果发现,根瘤菌接种后,白三叶草叶片含氮量明显增加,有3个基因型的根瘤菌接种植株后叶片氮含量达到对照的3倍以上,据此可根据根瘤菌的基因型来预测其固氮效率,共生固氮效率与根瘤菌基因型的关系较与分离宿主的关系更加密切。在中度干旱胁迫下,白三叶草植株地上部生物量积累所受影响较地下部所受影响更大,在白三叶草与根瘤菌共生体系建立过程中,当根瘤菌固定的氮素可以满足植株生长需要时,干旱胁迫可能成为生长的限制因子。     

Seed coating with inocula of arbuscular mycorrhizal fungi and plant growth promoting rhizobacteria for nutritional enhancement of maize under different fertilisation regimes

Arbuscular mycorrhizal (AM) fungi and plant growth-promoting rhizobacteria, responsible for enhancing plant nutrition, vigour and growth, may be used to reduce dosages of chemical fertilisers. Technologies that allow an economically viable and efficient application of these beneficial microbes in large scale agriculture must be studied. Seed coating is a potential delivery system for efficiently introducing minor amounts of bioinoculants. Despite the dramatic reduction on inoculum dose per plant, inoculation of AM fungi via seed coating was as effective as conventional soil inoculation. Fertilisation and inoculation had a significant impact on maize shoots nutrient concentrations. Different fertilisation regimes did not influence mycorrhizal colonisation. Plants without fertilisation and singly inoculated with R. irregularis showed shoot nutrient concentration increments of 110, 93, 88 and 175% for nitrogen, phosphorus, potassium and zinc, respectively, comparing with non-inoculated controls. Plants singly inoculated with P. fluorescens via seed coating under full fertilisation, presented enhancements of 100, 75 and 141% for magnesium, zinc and manganese, respectively, comparing with non-inoculated controls. Seed coating is a promising tool for delivering microbial inoculants into the soil, while promoting sustainable production of maize. This technology is particularly pertinent in low input agriculture, with potential environmental profits and food quality improvements.     

RESPONSE OF MAIZE GROWN IN AN ALFISOL OF SRI LANKA TO INOCULANTS OF PLANT GROWTH PROMOTING RHIZOBACTERIA

Field experiments were conducted to assess the ability of rhizobacterial inoculants to enhance growth and yield of maize. Performances of two phosphorus (P)-solubilizing bacteria in combination with a fertilizer mixture containing rock phosphate and triple super phosphate (PFM), and five diazotrophs combining either with 150 kg or 100 kg nitrogen (N) ha^?1 supplied as urea were compared with non-inoculated-fertilized controls. Shoot P and N and soil available P and N contents were assessed and shoot biomass and ear weights were recorded at harvest. Pseudomonas cepacia resulted in significantly higher available P (51 mg P kg^?1 soil), P accumulation (3.6 g kg^?1 dry matter) and 13% increase in shoot biomass over control. Azospirillum sp. and dual inoculant comprising Enterobacter agglomerans + Agrobacterium radiobacter led to significantly higher available N (74–94 mg kg^?1 soil) and 19 to 26% increase in shoot biomass over the control. However, inoculants did not increase the yield significantly.     

Interaction Effects of Nitrogen and Phosphorus on Nodulation in Red Clover (Trifolium pratense L.)

Red clover (Trifolium pratense L.) is one of the most important plants in forage production, especially in northern areas. Fertilisation practices are focused on high yield and forage quality but effects of nutrients on nodulation and N₂ fixation are poorly understood. The aim of this work was to study how nitrogen (N) and phosphorus (P) separately as well as in combination affected nodulation. Red clover plants were grown in pots with gravel in a greenhouse for 11 weeks. To resemble field conditions the root temperature was kept lower than the shoot temperature. Plants were given five different combinations of N and P concentrations during growth. The result showed that at high N concentrations P had a counteracting effect on the N inhibition. The N₂-fixation parameters, nodule number, nodule dry matter and specific nitrogenase activity, were six times higher in plants grown with high N and high P than in plants with high N and low P. When the N₂-fixation parameters and the dry matter of roots and shoots were related to total plant dry matter, there was a stronger effect of P on nodulation parameters than on roots and shoots. This indicates that P has a direct effect on the N₂-fixation parameters, rather than an indirect effect via increased plant growth. These results demonstrate the importance to studying the effects of more than one nutrient at a time.     

Effect of Azospirillum brasilense inoculation on root morphology and respiration in tomato seedlings

Summary The level of Azospirillum brasilense strain Cd colonization in the rhizosphere of some vegetables was 10⁴–10⁵ colony-forming units (CFU) per root of one plant in 2-week-old plants inoculated with 5 × 10⁸ Azospirillum cells. Significant increases in root length (35%) and in top (90%) and root (50%) dry weight and total leaf area (90%) were observed in 18-day-old inoculated tomato plants compared with non-inoculated controls. An inoculum concentration of 1 × 10⁸ to 5 × 10⁸ CFU/ml stimulated the appearance of root hairs. Large numbers of bacteria (1 × 10⁹ CFU/ml) caused asymmetrical growth of the root tip. In a petri dish system, Azospirillum (1 × 10⁸ CFU/ml) increased root dry weight (150%), protein content (20%), respiration rate per root (70%) and the specific activity of malate dehydrogenase (45%–65%) over non-inoculated controls. The specific respiration rate, expressed as micromol of O₂ per minute per milligram of dry weight of roots, was significantly lower in inoculated roots, suggesting that less energy was spent for accumulation of more dry material.     

Seed inoculation with <Emphasis Type="Italic">Bacillus</Emphasis> spp. improves seedling vigour in oil-seed plant <Emphasis Type="Italic">Jatropha curcas</Emphasis> L.

Jatropha (Jatropha curcas L.) is a non-edible oil-seed plant with adaptability to marginal semi-arid lands and wastelands. The Indian Government is promoting jatropha to reduce dependence on the crude oil and to achieve energy independence by the year 2012, under the National Biodiesel Mission. Selected strains of Bacillus spp., either supplemented with or without chitin, were tested for their ability to promote growth of jatropha seedlings in pot culture studies. The strains supported growth of jatropha seedlings up to 42 days after sowing. Among all strains, Bacillus pumilus (IM-3) supplemented with chitin showed over all plant growth promotion effect resulting in enhanced shoot length (113%), dry shoot mass (360%), dry root mass (467%), dry total plant mass (346%), leaf area (256%), and chlorophyll content (74%) over control. Treating seeds with strain IM-3 without chitin resulted in enhanced dry shoot mass (473%), dry total plant mass (407%), and chlorophyll content (82%). However, Bacillus polymyxa (KRU-22) with chitin supported maximum root length (143%). Either strain IM-3 alone or in combination with other promising strains could be promoted further for enhanced initial seedling growth of jatropha.     

Seedling vigor and nitrogen use efficiency of Moroccan wheat as influenced by level of soil nitrogen

Abstract

One of the characteristics that can help wheat (Triticum aestivum L.) plants escape late season drought in the semiarid areas of Morocco is early stand establishment and adequate vigor. Little is known about the effect of nitrogen (N) on early seedling vigor in wheat. The objective of this study was to determine how N supply affects early root and shoot growth, N partitioning between the two parts and N use efficiency of seedlings. To reach this objective, three spring wheat cultivars were grown in pots in a growth chamber under N conditions which were low, adequate and high. Data showed that optimum N rates increased shoot and root growth but high N concentrations reduced their dry matter accumulation and inhibited root elongation. The cultivars tested behaved differently. ‘Nesma’, an older cultivar, produced 60% more dry matter and accumulated 93% more N in the shoot and root than the newer cultivars ‘Merchouch 8’ and ‘Saada’. Because of its high N uptake, ‘Nesma’ probably reduced soil N concentration at the root zone and avoided the negative effect of high N concentration on root growth. Although, ‘Nesma’ performed better and produced more dry matter, it used N less efficiently than the other two cultivars.

From this study, we can conclude that use of optimum N rates at time of seeing will result in quicker establishment and higher vigor of wheat seedlings. However, excessive N supply may retard seedling growth. The cultivars that produce more seedling dry matter with greater N accumulation are not necessarily the ones that use N more efficiently.     

Phosphorus bioavailability of sewage sludge‐based recycled fertilizers

Six phosphorus (P) fertilizers recycled from sewage sludge [Struvite SSL, Struvite AirPrex®, P‐RoC®, Mephrec®, Pyrolysis coal and Ash (Mg‐SSA)] were tested for their plant availability in potted soil of pH 7.2 under greenhouse conditions. The crop sequence simulated a rotation of red clover (Trifolium pratense L.), maize (Zea maize L.), and ryegrass (Lolium perenne L.). Other P fertilizer treatments included: Phosphate Rock (PR), Calcium dihydrogen phosphate [Ca(H₂PO₄)₂], and an unfertilized control. Additionally, soil was regularly inoculated with two strains of plant growth‐promoting rhizobacteria (PGPR; Pseudomonas sp. Proradix, and Bacillus amyloliquefaciens) to test their ability to increase P availability to plants. Sequential P fractionation was conducted to link the amount of readily available P in fertilizers to plant P acquisition. Shoot P content and dry matter of maize decreased in the following order: Struvite SSL ≥ Ca(H₂PO₄)₂ > P‐RoC® ≥ Struvite AirPrex® ≥ Mephrec® > Pyrolysis coal ≥ Mg‐SSA ≥ PR ≥ unfertilized. Rhizobacteria did not affect shoot biomass or P content. The results show that red clover might have mobilized substantial amounts of P. Sequential P fractionation was not suitable to predict the efficacy of the fertilizers. Generally, the sewage sludge‐based fertilizers tested proved to be suitable alternative P sources relevant to organic farming systems. However, the efficacy of recycled fertilizers is strongly dependent on their specific production conditions.