Isolation and identification of endophytic bacteria from root tissues of Salvia miltiorrhiza Bge. and determination of their bioactivities

Endophytic bacteria are microorganisms that live in host plants, but do not cause diseases to the hosts. This study examined the occurrence, distribution, growth-promoting and antifungal activities of endophytes in the root of Salvia miltiorrhiza Bge. Six endophytic bacterial strains, which belong to genera of Pseudomonas, Rhizobium, Bacillus and Novosphingobium, were isolated from the root of healthy S. miltiorrhiza. Cell suspension (approx. 10⁹ cell?·?ml^?1) of two isolates and cell-free fermentation filtrate of four isolates substantially promoted the growth of hypocotyl and radicle of muskmelon seeds. The cell-free fermentation filtrate of six isolates had no inhibiting effect on tested pathogenic fungi, namely Fusarium solani, F. oxysporum f. sp. vasinfectum and F. oxysporum. Six compounds were isolated from one of the six endophytic bacteria, namely, Bacillus aryabhattai, and two of these compounds displayed certain antifungal activity against three tested S. miltiorrhiza pathogens. Our work indicates that endophytic bacteria occur in the root of S. miltiorrhiza, and that associated bacterial isolates have growth-promoting effect on muskmelon seeds and are expected to be a potential source for bioactive metabolites.     

Effects of take-all (Gaeumannomyces graminis var. tritici) on crop N uptake and residual mineral N in soil at harvest of winter wheat

Background and aims

Take-all, caused by the fungus Gaeumannomyces graminis var. tritici, is the most damaging root disease of wheat. A severe attack often leads to premature ripening and death of the plant resulting in a reduction in grain yield and effects on grain quality (Gutteridge et al. in Pest Manag Sci 59:215–224, 2003). Premature death of the plant could also lead to inefficient use of applied nitrogen (Macdonald et al. in J Agric Sci 129(2):125–154, 1997). The aim of this study was to determine crop N uptake and the amount of residual mineral N in the soil after harvest where different severities of take-all had occurred.

Methods

Plant and soil samples were taken at anthesis and final harvest from areas showing good and poor growth (later confirmed to be caused by take-all disease) in three winter wheat crops grown on the same soil type on Rothamsted Farm in SE England in 1995, 2007 and 2008 (harvest sampling only). All crops received fertiliser N in spring at recomended rates (190–200?kg?N ha^?1). On each ocassion crops were assessed for severity of take-all infection (TAR) and crop N uptakes and soil nitrate plus ammonium (SMN) was determined. Grain yields were also measured.

Results

Grain yields (at 85% dry matter) of crops with moderate infection (good crops) ranged from 4.3 to 13.0?t ha^?1, compared with only 0.9–4.5?t ha^?1 for those with severe infection (poor crops). There were significant (P?<?0.05) negative relationships between crop N uptake and TAR at anthesis and final harvest. At harvest, good crops contained 129–245?kg?N ha^?1 in grain, straw and stubble, of which 85–200?kg?N ha^?1 was in the grain. In contrast, poor crops contained only 46–121?kg?N ha^?1, of which only 22–87?kg?N ha^?1 was in the grain. Positive relationships between SMN and TAR were found at anthesis and final harvest. The SMN in the 0–50?cm layer following harvest of poor crops was significantly (P?<?0.05) greater than that under good crops, and most (73–93%) was present as nitrate.

Conclusions

Localised patches of severe take-all infection decreased the efficiency with which hexaploid wheat plants recovered soil and fertiliser derived N, and increased the subsequent risk of nitrate leaching. The risk of gaseous N losses to the atmosphere from these areas may also have been enhanced.     

A combination of humic substances and Herbaspirillum seropedicae inoculation enhances the growth of maize (Zea mays L.)

Background

Endophytic diazotrophic bacteria colonize several non-leguminous plants and promote plant growth. Different mechanisms are involved in bacteria-induced plant growth promotion, including biological nitrogen fixation (BNF), mineral solubilization, production of phytohormones, and pathogen biocontrol. Herbaspirillum seropedicae is a broad-host-range endophyte that colonizes sugarcane, rice, wheat, sorghum, and maize, and has been used as a biofertilizer. Contrasting results between greenhouse and field experiments have prompted efforts to improve the consistency of the plant response to microbial stimulation.

Aims

The aim of this study was to evaluate the effect of the presence of humic substances on inoculation of maize (Zea mays L.) with H. seropedicae.

Methods

Two experiments were conducted: one in the greenhouse using sand and nutrient solution and the other a field trial in soil with low natural fertility and to which was applied N in the form of urea (50 kg ha^?1). In the greenhouse, pre-emerging seeds were inoculated with a solution of H. seropedicae (10⁹ cells mL^?1) in the presence of humic substances isolated from vermicompost (10, 20, or 30 mg C?L^?1); in the field trial, bacteria combined with humate were added as a foliar spray (450 L?ha^?1).

Results

At early stages (7 and 45 days old) in the greenhouse, the treatment activated plant metabolism including enhancement of plasma membrane H⁺-ATPase activity, alteration of sugar and N metabolism, and greater net photosynthesis. The number of viable bacterial cells was higher in root tissues when inoculation was in the presence of soluble humic substances. Foliar application of endophytic diazotrophic bacteria and humic substances increased maize grain production 65 % under field conditions. These results show a promising use of humic substances to improve the benefit of endophytic diazotrophic inoculation.     

Co-inoculation with <Emphasis Type="Italic">Enterobacter</Emphasis> and Rhizobacteria on Yield and Nutrient Uptake by Wheat (<Emphasis Type="Italic">Triticum aestivum</Emphasis> L.) in the Alluvial Soil Under Indo-Gangetic Plain of India

The aim of this work was to evaluate the effects of co-inoculation with phosphate-solubilizing and nitrogen-fixing rhizobacteria on growth promotion, yield, and nutrient uptake by wheat. Out of twenty-five bacteria isolated from the rhizosphere soils of cereal, vegetable, and agro-forestry plants in eastern Uttar Pradesh, three superior most plant growth-promoting (PGP) isolates were characterized as Serratia marcescens, Microbacterium arborescens, and Enterobacter sp. based on their biochemical and 16S rDNA gene sequencing data and selected them for evaluating their PGP effects on growth and yield of wheat. Among them, Enterobacter sp. and M. arborescens fixed significantly higher amounts (9.32?±?0.57 and 8.89?±?0.58 mg Ng^?1 carbon oxidized, respectively) of atmospheric nitrogen and produced higher amounts (27.06?±?1.70 and 26.82?±?1.63 TP 100 µg mL^?1, respectively) of IAA in vitro compared to S. marcescens (8.32?±?0.39 mg Ng^?1 carbon oxidized and 21.29?±?0.99 TP 100 µg mL^?1). Although both M. arborescens and S. marcescens solubilized remarkable amounts of phosphate from tricalcium phosphate likely through production of organic acids, however, Enterobacter sp. was inactive. The effects of these three rhizobacteria were evaluated on wheat in alluvial soils of the Indo-Gangetic Plain by inoculation of plants with bacterial isolates either alone or in combinations in both pot and field conditions for two successive years. Rhizobacterial inoculation either alone or in consortium of varying combinations significantly (P?≤?0.05) increased growth and yield of wheat compared to mock inoculated controls. A consortium of two or three rhizobacterial isolates also significantly increased plant height, straw yield, grain yield, and test weight of wheat in both pot and field trials compared to single application of any of these isolates. Among the rhizobacterial treatment, co-inoculation of three rhizobacteria (Enterobacter, M. arborescens and S. marcescens) performed best in promotion of growth, yield, and nutrient (N, P, Cu, Zn, Mn, and Fe) uptake by wheat. Taken together, our results suggest that co-inoculation of Enterobacter with S. marcescens and M. arborescens could be used for preparation of an effective formulation of PGP consortium for eco-friendly and sustainable production of wheat.     

Seed yield,head characteristics and oil content in sunflower varieties as influenced by seeds from single and multiple headed plants under humid tropical conditions

Field trials were conducted during 2004 and 2005 to determine the effect of sowing seeds from plants with multiple heads and seeds from single headed plants of sunflower on seed yield, head characteristics and oil content of three widely grown open pollinated varieties (Funtua, Record and Isaanka) in the humid forest—savanna transition zone which is outside the current growing areas with a view to improving stability and sunflower productivity in this region. Seeds from multiple headed plants produced plants that flowered and matured 2–3 days later than plants from single headed plants. Apart from days to flowering in 2004, number of days to maturity and plant height were affected independently by variety and seed source factors. However, the seeds from single headed plants produced plants that recorded significantly (P < 0.01) higher head weight, head diameter, achene weight and number per head than plants from seeds of plants with multiple heads. Seed source had little effect on sunflower seed yield and oil content. However, Funtua produced significantly (P < 0.05) high seed yield (1956.0 kg ha^?1 ± 76.06) when seeds from plants with multiple heads were sown, while Isaanka recorded comparatively high seed yield from seeds of plants from either multiple (1221.0 kg ha^?1 ± 165.90) or single heads (1388.0 kg ha^?1 ± 135.84) and Record (1201.0 kg ha^?1 ± 96.97) when seeds from single headed plants were sown. Therefore, it is recommended that prospective sunflower growers who wish to cultivate Isaanka, can sow seeds from either the multiple or single head and preferably the multiple head for Funtua, and single head for Record.     

Biomass Yield and Nutrient Removal Rates of Perennial Grasses under Nitrogen Fertilization

Perennial grasses may provide a renewable source of biomass for energy production. Biomass yield, nutrient concentrations, and nutrient removal rates of switchgrass (Panicum virgatum L.), giant miscanthus (Miscanthus x giganteus), giant reed (Arundo donax L.), weeping lovegrass [Eragrostis curvula (Shrad.) Nees], kleingrass (Panicum coloratum L.), and Johnsongrass (Sorghum halepense (L.) Pers.) were evaluated at four N fertilizer rates (0, 56, 112, or 168?kg?N?ha^?1) on a Minco fine sandy loam soil in southern Oklahoma. Species were established in 2008 and harvested for biomass in winter of 2009 and 2010. Biomass yield (dry matter basis) did not show a strong relationship with N fertilizer rate (p?=?0.08), but was affected by year and species interactions (p?<?0.01). Weeping lovegrass and kleingrass produced 29.0 and 16.0?Mg?ha^?1 in 2009, but only 13.0?Mg?ha^?1 and 9.8?Mg?ha^?1 in 2010, respectively. Biomass yields of giant reed, switchgrass, and Johnsongrass averaged 23.3, 17.8, and 6.0?Mg?ha^?1, respectively. Giant miscanthus established poorly, producing only 4.7?Mg?ha^?1. Across years, giant reed had the highest biomass yield, 33.2?Mg?ha^?1 at 168?kg?N?ha^?1, and the highest nutrient concentrations and removal rates (162 to 228?kg?N?ha^?1, 23 to 25?kg?P?ha^?1, and 121 to 149?kg?K?ha^?1) among the grasses. Although giant reed demonstrated tremendous biomass production, its higher nutrient removal rates indicate a potential for increased fertilization requirements over time. Switchgrass had consistently high biomass yields and relatively low nutrient removal rates (40 to 75?kg?N?ha^?1, 5 to 12?kg?P?ha^?1, and 44 to 110?kg?K?ha^?1) across years, demonstrating its merits as a low-input bioenergy crop.     

Bacterial community compositions of tomato (Lycopersicum esculentum Mill.) seeds and plant growth promoting activity of ACC deaminase producing Bacillus subtilis (HYT-12-1) on tomato seedlings

Study of endophytic bacteria within plant seeds is very essential and meaningful on account of their heritability and versatility. This study investigated Bacillus bacterial communities within the seeds of four commercial tomato varieties, by 16S rRNA gene PCR-RFLP (restriction fragment length polymorphism). Phylogenetic analysis of 16S rRNA gene sequences indicated that the 22 representative isolates belonged to five species of genus Bacillus and the bacterial compositions showed remarkable differences among tomato varieties. Isolates exhibited multiple plant growth promoting (PGP) traits: 37 % of indole-3-acetic acid production; 37 % of phosphate solubilization; 24 % of siderophores production; 85 % of potential nitrogen fixation and 6 % of 1-aminocyclopropane-1-carboxylate (ACC) deaminase activity. Isolate HYT-12-1 was shown to have highest ACC deaminase activity (112.02 nmol α-ketobutyrate mg^?1 protein h^?1) among the five ACC deamiase producing strains. 16S rRNA gene sequencing indicated that the isolate HYT-12-1 shared the highest sequence similarity (100 %) with B. subtilis. PGP experiments under gnotobiotic and greenhouse conditions revealed the ability of strain HYT-12-1 to enhance the growth of tomato seedlings. This is the first study to describe endophytic Bacillus communities within tomato seeds, and the results suggest that B. subtilis strain HYT-12-1 would have a great potential for industrial application as biofertilizer in the future.     

Gross precipitation and throughfall chemistry in legume species planted in Northeastern México

Plant cover modifies throughfall chemistry, and the solute concentration is dependent on the plant species at any given site. The chemistry of gross rainfall and throughfall of four endemic species planted in northeastern Mexico was evaluated from March 1996 to March 1997. Chemical solutes measured included Ca, K, Mg, Na, Fe, Mn, Cu, and Zn. Dry deposition and canopy leaching fluxes were estimated following the canopy budget model. Variance analyses tested the statistical dependence of the total and net fluxes on the species and seasons. Regression analysis tested the dependence of chemical concentrations on rainfall depth and lag time between rains. A total of 52 rainfall events were recorded during the study period summing 523 mm. Significant differences were noted on the total and net fluxes between the plant species. For total flux, average throughfall (37.8 kg ha^?1 year^?1) almost doubled the flux of solutes compared to rainfall (24.1 kg ha^?1 year^?1). Pithecellobium ebano (Berland.) C.H. Mull. (43.3 kg ha^?1 year^?1), Acacia berlandieri Benth. (38.7 kg ha^?1 year^?1), and Pithecellobium pallens (Bent.) Standl. (38.4 kg ha^?1 year^?1) recorded the highest total flux of solutes, and Acacia rigidula Benth. (30.9 kg ha^?1 year^?1) the smallest. Chemical solutes showed significant differences for total and net fluxes. Ca was the dominant cation with 48% and 52% of the total constituent flux for rainfall and throughfall, respectively. However, K, Mg and Cu approximately doubled in throughfall in contrast to gross rainfall. Species with the largest aboveground biomass had lower throughfall volumes (i.e., higher interception rates) but higher chemical solute inputs to the forest floor. Rainfall depth and lag time between rains explained part of the variation for most species, stressing the partial dependence of the washing effect and the amount of dry deposition on canopies. This research discusses the importance and the sources of incoming solutes on the studied plant species.     

Potential growth of alfalfa (Medicago sativa L.) in the desert of Southern Peru and its response to high NPK fertilization

Irrigated and highly fertilized alfalfa growing in the deserts of Southern Peru reached maximum growth rates of about 200 kg dry forage ha^?1 d^?1 during the summer period and of 150 kg ha^?1 d^?1 during winter. These high rates were maintained for 10 to 20 days, after which growth rates declined. ‘Ceiling’ yields of about 5000 kg dry forage ha^?1 in summer and 3500 kg ha^?1 in winter were obtained in a growth period of 53 days. Simulations with an adapted model indicate that a decreased photosynthetic rate for aging leaves is a probable cause for the decrease. Growth curve simulations were also very sensitive to the level of carbohydrate reserves in the root system at harvest. High NPK fertilization (420, 280 and 420 kg ha^?1 yr^?1 of urea-N, P and K respectively) increased NO₃?N in soil 2.5 fold, available-K 1.6 fold, and available-P 4.3 fold. NH₄?N content did not increase. The higher amounts of available nutrients resulted in only about 10 percent increases in maximum growth rate and maximum yields. With respect to plant composition (%N, %P and %K), a significant response only to the higher P level was observed and a very slight, non-significant response to the higher K level was also noted. High N-fertilization did not increase the N-content of the plant, indicating that the rhizobia present are able to fix up to 900–1000 kg N ha^?1 yr^?1 in the aboveground herbage. Commercial inoculants did not improve this N-fixation capacity; even in virgin desert soils after only a few harvests, yields as well as N-contents of non-inoculated alfalfa were of the same order of magnitude as inoculated alfalfa.     

Optimizing Sweet Sorghum Production for Biofuel in the Southeastern USA Through Nitrogen Fertilization and Top Removal

Sustainable bioenergy cropping systems require not only high yields but also efficient use of inputs. Management practices optimizing production of sweet sorghum [Sorghum bicolor (L.) Moench] for bioenergy use are needed. The effects of N rate (45, 90, 135, and 180?kg N?ha^?1) and top removal (at boot stage, anthesis, and none) on biomass, brix, estimated sugar yield, and N and P recovery of sweet sorghum cv. M-81E were investigated in Florida at two sites differing in soil type. Across all data, dry biomass yields averaged 17.7 Mg?ha^?1 and were not affected by N fertilization rate at either site (P?>?0.10). Mean brix values ranged from 131 to 151?mg?g^?1 and were negatively related to N rate. Top removal, either at boot stage or anthesis, resulted in greater brix values and 13% greater sugar yields at both locations. Whole plant N recovery was positively and linearly related to N rate and ranged from 78 to 166?kg N?ha^?1, approximately two thirds of which was in leaf and grain tissues. Based on yield and nutrient recovery responses, optimal nutrient requirements were 90 to 110?kg N?ha^?1 and 15 to 20?kg P?ha^?1. Higher N fertilization led to greater N recovery, but little to modest gain in sugar yield. Thus, proper nutrient and harvest management will be needed to optimize sugar yields of sweet sorghum for production of biofuels and bio-based products. Further research is needed to refine management practices of sweet sorghum for bioenergy production, especially with regard to the use of leaf and grain tissues.     

Effect of tillage system on the root growth of spring wheat

Little research has examined the influence of tillage system on root growth in wheat grown on rainfed Vertisols. A 3-year field study (2003, 2004 and 2005) was carried out on a typical Vertisol (southern Spain), to determine the effects of tillage system on root growth in spring wheat (Triticum aestivum L) grown in continuous rotation with faba bean (Vicia faba L), within the framework of the long-term “Malagón” experiment started in 1986. Tillage treatments were no-tillage (NT) and conventional tillage (CT), and the experiment was designed as a randomized complete block with three replications. The following parameters were measured: above-ground biomass, grain yield, root length density (RLD), root biomass (RB) and root N content. In the topmost 10 cm of soil, higher values were found under CT than under NT for RLD in the rainiest year (20.2 km m^?3 vs. 9.6 km m^?3 respectively) and for RB (512 kg ha^?1 vs. 261 kg ha^?1 respectively) in all study years. In deeper layers, no difference was recorded between the two tillage systems. Greater wheat root development in the upper soil layer under CT may reflect the greater soil penetration resistance found in the topmost 10 cm under NT. Root separation using a sieve with a 0.5 mm mesh screen led to a marked underestimation of RLD and RB, with values up to three times higher when using a 0.2 mm mesh screen. Mean wheat root N content in the topmost 30 cm of soil accounted for over 80% of total root N content. The highest grain yield was observed under NT, since this system provided greater water storage in the soil profile in the mostly dry study years.     

Biomass Yield and Nutrient Responses of Switchgrass to Phosphorus Application

Increasing desire for renewable energy sources has increased research on biomass energy crops in marginal areas with low potential for food and fiber crop production. In this study, experiments were established on low phosphorus (P) soils in southern Oklahoma, USA to determine switchgrass biomass yield, nutrient concentrations, and nutrient removal responses to P and nitrogen (N) fertilizer application. Four P rates (0, 15, 30, and 45?kg?P?ha^?1) and two N fertilizer rates (0 and 135?kg?N?ha^?1) were evaluated at two locations (Ardmore and Waurika) for 3?years. While P fertilization had no effect on yield at Ardmore, application of 45?kg?P?ha^?1 increased yield at Waurika by 17% from 10.5 to 12.3?Mg?ha^?1. Across P fertilizer rates, N fertilizer application increased yields every year at both locations. In Ardmore, non-N-fertilized switchgrass produced 3.9, 6.7, and 8.8?Mg?ha^?1, and N-fertilized produced 6.6, 15.7, and 16.6?Mg?ha^?1 in 2008, 2009, and 2010, respectively. At Waurika, corresponding yields were 7.9, 8.4, and 12.2?Mg?ha^?1 and 10.0, 12.1, and 15.9?Mg?ha^?1. Applying 45?kg?P?ha^?1 increased biomass N, and P concentration and N, P, potassium, and magnesium removal at both locations. Increased removal of nutrients with N fertilization was due to both increased biomass and biomass nutrient concentrations. In soils of generally low fertility and low plant available P, application of P fertilizer at 45?kg?P?ha^?1 was beneficial for increasing biomass yields. Addition of N fertilizer improves stand establishment and biomass production on low P sites.     

Water chemistry and nutrient budgets in an undisturbed evergreen rainforest of Southern Chile

In a pristine evergreen rainforest of Nothofagus betuloides, located at the Cordillera de los Andes in southern Chile (41?°S), concentrations and fluxes of nutrients in bulk precipitation, cloud water, throughfall water, stemflow water, soil infiltration and percolation water and runoff water were measured. The main objectives of this study were to investigate canopy–soil–atmosphere interactions and to calculate input–output budgets. From May 1999 till April 2000, the experimental watershed received 8121?mm water (86% incident precipitation, 14% cloud water), of which the canopy intercepted 16%. Runoff water volume amounted 9527?mm. Bulk deposition of inorganic (DIN) and organic (DON) nitrogen amounted 3.6?kg?ha^?1?year^?1 and 8.2?kg?ha^?1?year^?1 respectively. Occult deposition (clouds?+?fog) contributes for 40% to the atmospheric nitrogen input (bulk?+?occult deposition) of the forest. An important part of the atmospheric ammonium deposition is retained within the canopy or converted to nitrate or organic nitrogen by epiphytic bacteria or lichens. Also the export of inorganic (0.9?kg?ha^?1?year^?1) and organic (5.2?kg?ha^?1?year^?1) nitrogen via runoff is lower than the input to the forest floor via throughfall and stemflow water (3.2?kg?DIN?ha^?1?year^?1 and 5.6?kg?DON?ha^?1?year^?1). The low concentrations of NO-₃ and NH+₄ under the rooting depth suggest an effective biological immobilization by vegetation and soil microflora. Dry deposition and foliar leaching of base cations (K⁺, Ca²⁺, Mg²⁺) was estimated using a canopy budget model. Bulk deposition accounted for about 50% of the total atmospheric input. Calculated dry and occult deposition are both of equal value (about 25%). Foliar leaching of K⁺, Ca²⁺, and Mg²⁺ accounted for 45%, 38% and 6% of throughfall deposition respectively. On an annual basis, the experimental watershed was a net source for Na⁺, Ca²⁺ and Mg²⁺.     

Germination, field establishment patterns and nitrogen fixation of indigenous legumes on nutrient-depleted soils

Integrating N₂-fixing indigenous legumes in smallholder farming systems has potential to alleviate some of the major soil fertility constraints associated with lack of nitrogen (N) inputs in many parts of Sub-SaharanAfrica. Studies were conducted under low (450–650 mm yr^?1) and high (>800 mm yr^?1) rainfall areas in Zimbabwe to investigate the establishment and nitrogen fixation patterns of fifteen indigenous legume species. The legume seeds were broadcast in mixtures at 120 seeds m^?2 species^?1 during 2004/05 and 2005/06 rainfall seasons.Eriosema ellipticum, Crotalaria ochroleuca andC. pallida had emergence rates above 15% compared with <10% forTephrosia radicans andIndigofera astragalina. Seed hardness accounted for >50% germination failure, while low viability explained 10–30%.Crotalaria ochroleuca andC. pallida attained a maximum biomass of 5–9 t ha^?1 (dry weight) over six months, while species that reached peak biomass over three months (e.g.C. cylindrostachys andC. glauca) gave lowest yields of ≈0.5 t ha^?1. Biennials,Neonotonia wightii, E. ellipticum and Tephrosia radicans, exhibited slow growth rates and only attained their maximum biomass of ≈2 t ha^?1 in the second season. The legumes derived 60–99% of their N from the atmosphere, fixing 5–120 kg N ha^?1 under low rainfall and 78–267 kg N ha^?1 under high rainfall. These findings suggest that the legumes could contribute in restoring productivity of soils continuously cultivated with little or no nutrient inputs in most of Zimbabwe and similar agro-ecologies in SubSaharan Africa.     

Effects of cryopreservation of Phaseolus vulgaris L. seeds on early stages of germination

In this work, we studied the effects of cryopreservation on various parameters of early stages of germination of Phaseolus vulgaris seeds (0, 7 and 14?days). Percentages of germination, fresh mass of different plant parts, levels of chlorophyll pigments (a, b, total), malondialdehyde, other aldehydes, phenolics (cell wall-linked, free, and total) and protein were determined. No phenotypic changes were observed visually in seedlings recovered from cryopreserved seeds. However, several significant effects of seed liquid nitrogen exposure were recorded at the biochemical level. There was a significant negative effect of cryopreservation on shoot protein content, which decreased from 3.11?mg?g^?1 fresh weight for non-cryopreserved controls to 0.44?mg?g^?1 fresh shoot weight for cryopreserved seeds. On the other hand, cryopreservation significantly increased levels of other aldehydes than malondialdehyde in shoots at day 7, from 56.47?μmol?g^?1 for non-cryopreserved controls to 253.19?μmol?g^?1 fresh shoot weight for cryopreserved samples. Liquid nitrogen exposure significantly reduced phenolics contents (free, cell-wall linked, total) in roots at day 7 after onset of germination. In general, roots were more affected by cryostorage compared with other plant parts, while leaves were the least affected. The effects of seed cryopreservation seem to decline progressively along with seedling growth.     

Systemic control efficacy of neonicotinoids seeds dressing on English grain aphid (Hemiptera: Aphididae)

English grain aphid, Sitobion avenae (Fabricius) (Hemiptera: Aphididae), is an important pest of wheat (Triticum aestivum L.), and is usually controlled by intensive foliar sprays of pesticides under field conditions. In order to reduce labour costs and increase the utilization of pesticides, neonicotinoids seed treatment was studied as a simple and accurate control technology for S. avenae. We evaluated the mortality of imidacloprid, acetamiprid, thiamethoxam, clothianidin, nitenpyram and dinotefuran to the English grain aphid by seed dressing methods in the laboratory, and found that the toxicity with that LC₅₀ of clothianidin (20.97?a.i.?g/100?kg seeds) and thiamethoxam (28.84?a.i.?g/100?kg seeds) to S. avenae are higher than other neonicotinoids. LC₅₀ values of nitenpyram, imidacloprid and acetamiprid ranged between 120?a.i.?g/100?kg seeds and 210?a.i.?g/100?kg seeds. Dinotefuran showed the lowest toxicity with LC₅₀ value 565.76?a.i.?g/100?kg seeds to English grain aphid. Field plot experiments were conducted to investigate the control efficacy of neonicotinoids seed treatment for the aphid, and the effects on growth of wheat. Field observations indicated that clothianidin and thiamethoxam provided the better control efficacy on the English grain aphid than imidacloprid, and had no influence on wheat seedling emergence. These results showed that seed treatment by neonicotinoids was effective against S. avenae throughout the growth period, furthermore, thiamethoxam and clothianidin were the effective and safe alternative options for S. avenae management in the crop.     

ACC deaminase containing diazotrophic endophytic bacteria ameliorate salt stress in Catharanthus roseus through reduced ethylene levels and induction of antioxidative defense systems

Among a total of 27 cultivable salt tolerant endophytic bacteria isolated from Catharanthus roseus grown in highly salt affected coastal region of cuddalore district, Tamilnadu, India four isolates were found to be positive for nitrogenase activity. The isolates were evaluated for their stress tolerance efficiency and screened for different PGP traits. Based on the above studied parameters, and ability to produce 1-aminocyclopropane-1-carboxylate (ACC) deaminase (4.24???mol ??-ketobutyrate mg^_1 protein h^_1) the salt tolerant diazotrophic isolate AUM54 was selected for further investigation and identified as Achromobacter xylosoxidans by 16S rRNA gene sequencing. The ability of this isolate to ameliorate salt stress in C. roseus was evaluated under gnotobiotic and pot culture conditions. At 150?mM NaCl level A. xylosoxidans AUM54 treated plants recorded ethylene level of 394.1 p mol ethylene g^?1 FW h^?1 compared to the ethylene level of 516.0 p mol ethylene g^?1 FW h^?1 recorded in the un inoculated control. A. xylosoxidans AUM54 inoculated plants recorded the maximum germination percentage of 98.3, vigor index of 2231.4, plant height of 120.4?cm, root dry weight of 53.24?g Plant^_1 and ajmalicine content of 1.60?mg?g^?1, compared to the germination percentage of 91.6%, vigour index of 1511.5, plant height of 105.8, root weight of 47.2?g Plant^?1, and ajmalicine content of 1.23?mg?g^?1 in uninoculated plants grown without NaCl treatment. This isolate also decreased plant ethylene levels by 11?C23% and increased the antioxidative enzyme content of inoculated C. roseus plants to the tune of 19?C32% for ascorbate peroxidase (APX) activity, 20?C30% for superoxide dismutase (SOD) activity and 4?C16% for catalase (CAT) under normal and salt affected conditions.     

Inoculation with selected strains of Azospirillum brasilense and A. lipoferum improves yields of maize and wheat in Brazil

Interest in the use of inoculants containing bacteria that promote plant growth is likely to increase in the coming years, due to higher costs of fertilizers, concerns over pollution and emphasis on sustainable agriculture. Although Brazil has a long tradition in research on nitrogen fixation in Azospirillum-grass associations, it has not led to recommendations of strains for use in commercial inoculants. In this study, we report the selection and evaluation of Azospirillum strains for the maize (Zea mays L.) and wheat (Triticum aestivum L.) crops, following protocols established by the Brazilian legislature, i.e. field experiments have to be performed in at least two different localities representing the crop growing regions, and for at least two seasons. In a first set of nine trials performed at Londrina and Ponta Grossa, southern Brazil, nine Azospirillum strains were evaluated after application to seeds as peat-based inoculants. A. brasilense strains Ab-V4, Ab-V5, Ab-V6 and Ab-V7 increased grain yields of maize by 662–823 kg ha^?1, or 24–30%, in relation to non-inoculated controls. Two A. lipoferum strains were tested in two of these experiments and promising results were also obtained. With wheat, A. brasilense strains Ab-V1, Ab-V5, Ab-V6 and Ab-V8 were the most effective, increasing yields by 312–423 kg ha^?1, or 13–18%. In a second trial set with eight field experiments at Londrina an Ponta Grossa, liquid and peat-based inoculants carrying a combination of A. brasilense strains Ab-V5 and Ab-V6 increased maize and wheat yields by 27% and 31%, respectively. Effects of inoculation were attributed to general increases in uptake of several macro and micronutrients and not specifically to biological nitrogen fixation. All experiments received only a low N-fertilizer starter at sowing (24 kg and 20 kg of N ha^?1 for the maize and wheat, respectively) and although yields can be globally considered low, they were compatible with Brazilian mean yields. This study resulted in the identification of the first Azospirillum strains authorized for the production of commercial inoculants in Brazil.     

N2 fixation in cowpea plants grown in farmers’ fields in the Upper West Region of Ghana, measured using15N natural abundance

Few studies have assessed the levels of symbiotic N nutrition in legumes grown by farmers in Africa. In this study, the shoots of cowpea plants were sampled from 63 farms in 12 villages within 5 districts of the Upper West Region of Ghana, and assessed for growth and symbiotic N nutrition. The data revealed considerable differences in cowpea plant density per m², plant growth,¹⁵N natural abundance (δ¹⁵N), %Ndfa, and N-fixed among different farms under one village, and between villages under the same district, and between districts in the Upper West Region. In farms where there were fewer cowpea plants per m², plant growth was better and dry matter yield per plant significantly greater, leading to strong variations in δ¹⁵N values. Except for four farms at Bamahu which had cowpea shoot Ndfa values of 12.1%, 30.0%, 36.5% and 46.6%, one farm at Babile with Ndfa value of 58.1%, and three farms at Silbelle with Ndfa values of 56.8%, 57.9% and 68.7%, the remaining 55 out of the 63 farms studied showed high shoot Ndfa values, ranging from 70.6% to 99.7%, which clearly indicates that cowpea cultivated by farmers in the Upper West Region of Ghana meet a large proportion of their N requirements from symbiotic fixation. At the district level, isotopic analysis showed that, on average, the¹⁵N natural abundance values (%0) of cowpea shoots were ?0.496±0.04 for Jirapa, ?0.083±0.06 for Nadowli, 0.368±0.08 for Lawra, J.333±0.29 for Wa and 0.365±0.09 for Sissala district. Estimates of the legume’s N derived from fixation were 66.3% for Wa district, 89.9% for Nadowli, 79.4% for Lawra, 78.9% for Sissala and 80.9% for Jirapa district. The amount of N-fixed ranged from 402.3 mg.plant^?1 for Nadowli, 176.5 mg.plant^?1 for Wa, 235.4 mg.plant^?1 for Sissala, 179.0 mg.plant^?1 for Lawra to 249.2 mg.plane^?1 for the Jirapa district. Expressed on per-hectare basis using cowpea density per m², the total amount of N-fixed was around 16.6 kg ha^?1 in the Nadowli district, 19.1 kg ha^?1 in Wa, 23.0 kg ha^?1 in Sissala, 2J.1 kg ha^?1 in Lawra and 17.6 kg ha^?1 in the Jirapa district. Averaged across all 5 districts, N-fixed by cowpea was about 19.5 kg ha^?1 in the Upper West Region of Ghana. These data suggest that, increasing N₂ fixation in fanners’ fields in Ghana would require optimization of cowpea plant density rather than biological manipulation of the symbiotic process (as %Ndfa values were generally very high).     

Risk of municipal solid waste compost and sewage sludge use on photosynthetic performance in common crop (<Emphasis Type="Italic">Triticum durum</Emphasis>)

The effect of composted municipal solid waste (MSW) and sewage sludge (SS) on photosynthetic activity of wheat (Triticum durum L.) was investigated. Chlorophyll fluorescence and gas exchange parameters were assessed following application of up to 300 t ha^?1 of MSW compost or SS. 100 t ha^?1 MSW compost was optimal for the plant growth, which showed 78% stimulation as compared to the control. This was associated with higher maximum quantum efficiency (F _v /F _m) of photosystem II (PSII) and the actual quantum efficiency of PSII open centers at light adapted state (ΔF/\(F_{\rm m}^{\prime}\)). Maximal values of net photosynthetic rate and stomatal conductance were recorded at 100 t ha^?1 MSW compost (+40 and +116%, respectively). Ribulose bisphosphate carboxylase/oxygenase (RubisCO) activity was also significantly stimulated at 100 t ha^?1, while less significant impact was found in SS treatment. A marked accumulation of Ni, Pb, Cu, and Zn in concomitance with membrane lipid peroxidation were observed at 200–300 t ha^?1 MSW compost and SS, resulting in lower photosynthetic activity and altered PSII functional integrity. Altogether, these results suggest that the MSW compost at 100 t ha^?1 would be suitable for wheat cultivation, within the critical limits of heavy metal accumulation. However, long-term field experiments seem necessary to more accurately evaluate the safety of MSW application.