Effect of Plant Growth Promoting Rhizobacteria on Fe Acquisition in Peach (Prunus Persica L) Under Calcareous Soil Conditions

Abstract

The effects of Alcaligenes 637Ca, Agrobacterium A18, Staphylococcus MFDCa1, MFDCa2, Bacillus M3 and Pantoea FF1 were tested on peach cv. ‘Elegant Lady’ on GF677 and Nemaguard rootstocks. Average increases in citric, malic, oxalic, butyric and fumaric acid in the leaf were obtained from rhizobacterial root inoculations of 33.1, 17.5, 21.7, 26.5, and 44.7% in Elegant Lady/Nemaguard, respectively. FF1 showed the highest FC-R activity in the roots of Nemaguard (112.4?nmol?FW?gr^?1?hr^?2) and GF677 (162?nmol?FW?gr^?1?hr^?2). The highest FC-R activity in the leaf was with MFDCa2 in Elegant Lady/Nemaguard (57.1?nmol?FW?gr^?1?hr^?2) and 637Ca in Elegant Lady/GF677 (87.9?nmol?FW?gr^?1?hr^?2). PGPR strains used in this study expressed increased leaf organic acid content, FC-R activity in the roots and leaf, increased active Fe content in the leaf, and possessed a great potential for the improvement of iron availability to plants.     

EFFECTS OF PLANT GROWTH PROMOTING BACTERIA ON YIELD,GROWTH, LEAF WATER CONTENT,MEMBRANE PERMEABILITY,AND IONIC COMPOSITION OF STRAWBERRY UNDER SALINE CONDITIONS

Plant growth promoting effects of Bacillus subtilis EY2, Bacillus atrophaeus EY6, Bacillus spharicus GC subgroup B EY30, Staphylococcus kloosii EY37 and Kocuria erythromyxa EY43 were tested on strawberry cv. ‘Fern’ in terms of fruit yield, growth, chlorophyll reading value, leaf relative water content (LRWC), membrane permeability and ionic composition of leaves and roots under saline conditions. Compared with 0 mM sodium chloride (NaCl) treatment, the average decrease of yield and LRWC were 51.6% and 21.0%, respectively, when 35 mM NaCl was applied. However, EY30, EY37, and EY43 treatments under saline condition (35 mM NaCl) significantly increased fruit yield (54.4%, 51.7% and 94.9%) compared with 35 mM NaCl treatment without plant growth promoting bacteria (PGPB). The LRWC increased from 72.0% in 35 mM NaCl treatment to 88.4%, 86.6%, 84.2%, 83.5%, and 86.2% by EY2, EY6, EY30, EY37, and EY43 applications, respectively. The lowest membrane permeability among the bacterial strains was obtained from EY37 treatment (37) while it was 33 and 58 in 0 mM NaCl and 35 mM NaCl treatments, respectively. The concentration of all plant tissue nutrients investigated [nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), and magnesium (Mg)] with the exception of root phosphorus (P) and Mg concentration significantly decreased with 35 mM salt treatment. Nitrogen content of leaves varied between 3.04 and 3.14% in bacterial treatments under saline conditions while it was 2.71% in 35 mM NaCl treatment. In contrast sodium (Na) and chloride (Cl) of leaves and Cl content of roots were significantly decreased by root inoculation with all bacterial treatments in comparison to 35 mM NaCl treatment with no inoculation. Treatment with Bacillus EY30, Staphylococcus EY37 and Kocuria EY43 to strawberry plants can ameliorative the deleterious effect of salt stress on fruit yield, growth and nutrition. These results demonstrate that PGPB treatment could be offer an economic and simple means to increased plant resistance for salinity stress.     

YIELD AND GROWTH RESPONSE OF STRAWBERRY TO PLANT GROWTH-PROMOTING RHIZOBACTERIA INOCULATION

This study was conducted to examine the effect of inoculation of plant growth-promotion Rhizobacteria (PGPR) on phenological data, total yield and fruit quality characteristics of strawberry (Fragaria x ananassa Duch) cv. ‘Fern’ during 2006 and 2007. All bacterial root inoculations significantly increased yield per plant (1.98–20.85%), average fruit weight (3.05–19.26%) and first quality fruit ratio (10.30–32.05%) compared to control, whereas the bacterial inoculations did not affect leaf area, first flowering and harvest dates in strawberry cv. ‘Fern’. The bacteria also increased soluble solid content (SSC) and vitamin C in strawberry cv. ‘Fern’. The vitamin C contents of fruits ranged from 47.41 mg 100 g^?1 (control) to 53.88 mg 100 g^?1 (RC05), while SSC values varied between 10.16% (control) and 12.83% (RC01). Results of this study show that RC19 (Bacillus simplex), RC05 (Paenibacillus polymyxa), and RC23 (Bacillus spp.) have the potential to increase the yield and growth of strawberries.     

Effects of phosphate‐solubilizing microorganisms on strawberry yield and nutrient concentrations

Phosphorus (P)‐solubilizing bacteria and fungi can increase soil‐P availability, potentially enhancing crop yield when P is limiting. We studied the effectiveness of Bacillus FS‐3 and Aspergillus FS9 in enhancing strawberry (Fragaria × ananasa cv. Fern) yield and mineral content of leaves and fruits on a P‐deficient calcareous Aridisol in Eastern Anatolia, Turkey. The 120 d pot experiment was conducted in three replicates with three treatments (Bacillus FS‐3, Aspergillus FS9, control) and five increasing rates of P addition (0, 50, 100, 150, and 200 kg P ha^–1). Fruit yield and nutrient content of fruits and leaves and soil P pools were determined at the end of the experiment. Phosphorus‐fertilizer addition increased all soil P fractions. Strawberry yield increased with P addition (quadratic function) reaching a maximum of 94 g pot^–1 at 200 kg P ha^–1 in the absence of P‐solubilizing microorganisms. At this yield level, Bacillus FS‐3 and Aspergillus FS9 inoculation resulted in P‐fertilizer savings of 149 kg P ha^–1 and 102 kg P ha^–1, respectively. Both microorganisms increased yields beyond the maximum achievable yield with sole P‐fertilizer addition. Microorganism inoculation increased fruit and leaf nutrient concentrations (N, P, K, Ca, and Fe) with the largest increases upon addition of Bacillus FS‐3. We conclude that Bacillus FS‐3 and Aspergillus FS9 show great promise as yield‐enhancing soil amendments in P‐deficient calcareous soils of Turkey. However, moderate additions of P fertilizer (50–100 kg ha^–1) are required for highest yield.     

Effects of Plant Growth Promoting Rhizobacteria on Yield and Some Fruit Properties of Strawberry

Effects of plant growth promoting rhizobacteria (PGPR) [(Pseudomonas BA-8 (biological control agent), Bacillus OSU-142 (N₂-fixing), and Bacillus M-3 (N₂-fixing and phosphate solubilizing)] on yield and some fruit properties of strawberry cultivar ‘Selva’ in the province of Erzurum, Turkey in 2002–2003. Foliar + root application of PGPR strains significantly increased yield per plant as compared with the control. Root application of PGPR strains significantly increased total soluble solids, total sugar and reduced sugar, but decreased titratable acidity. It was also determined that bacteria applications have no important effect on the average fruit weight and pH. The results of this study suggested that Pseudomonas BA-8, Bacillus OSU-142 and Bacillus M-3 have potential for increasing yield in strawberry plant.     

Exogenous applications of salicylic acid affect quality and yield of strawberry grown under antifrost heated greenhouse conditions

Abiotic stress is becoming more prevalent as the intensity of agriculture and the demand for farmable land are ever increasing. Besides drought and salinity stress, chilling or freezing stress is one of the most important limiting factors of crop production all around the world. Salicylic acid (SA) is a common plant‐produced signal molecule that is responsible for inducing resistance to a number of biotic and abiotic stresses. This study was conducted to determine the effect of foliar SA applications on fruit‐quality characteristics and yield of strawberry under antifrost heated greenhouse conditions in two successive experiments. Spraying of 1 mM SA (1 mM) was done once (SA1), twice (SA2), three times (SA3), or four times (SA4) during the vegetation period with 7 d intervals. Concentrations of chlorophyll and minerals were measured in leaves, and vitamin C (ascorbic acid), total soluble solids (TSS), titratable acidity (TA), and color (a*) in fruits. Fruit weight, early yield, and total yield were also determined. Foliar applications of SA positively affected TSS and ascorbic acid (AA) content of strawberry fruits. Salicylic acid treatments had no effect on TA of strawberry fruits. SA4 treatment gave the greatest a* in fruit and chlorophyll‐concentration values in the leaves. It was shown that SA treatments increased the content of all nutrients in the leaves of strawberry plants, and greater values often were obtained from SA3 and SA4 treatments. The early yield and total yield of strawberry were significantly affected by SA applications, among which SA3 and SA4 resulted in the highest early and total yields. The present study suggests that SA3 and SA4 treatments can ameliorate the deleterious effects of low temperatures on strawberry plants and that SA application may offer an economical and simple method for low‐temperature protection.     

Influence of humic acid and salicylic acid on yield,fruit quality,and leaf mineral elements of strawberry (Fragaria × Ananassa duch.) cv. Camarosa

A greenhouse experiment was conducted to evaluate the effects of foliarly-applied Humic Acid (HA) and Salicylic Acid (SA) on strawberry (Fragaria × Ananassa cv. Camarosa). On average, HA applications, regardless of concentration, increased overall yield, Soluble Solids Concentrations (SSC), Titratable Acidity (TA), vitamin C, red tone (a*), leaf potassium (K), phosphorus (P), calcium (Ca) and magnesium (Mg) while had no effect on pH and fruit luminosity (L*). In contrast, fruit from the untreated control tended to have higher Total Antioxidant Capacity (TAC) and SSC: TA ratio than HA-treated plants. Application of SA significantly increased yield, vitamin C, SSC, SSC: TA ratio, TAC, a*, leaf P and Ca while had no effect on TA, fruit size, L* and pH. In general, application of either HA at 25 mg L¹ or SA at 2 mM resulted in better strawberry performance than did other rates of these compounds.     

Nutritional Evaluation of Nitrogen and Potassium Fertilization of Carob Tree under Dry‐Farming Conditions

Abstract

The aim of this work was to assess how potassium (K) and nitrogen (N) fertilization might affect the variation of leaf and fruit nutrient concentrations in carob tree (Ceratonia siliqua L.) under low precipitation. A field study was conducted in 1997, 1998, and 1999 in a calcareous soil. Four fertilization treatments were tested: no fertilizer (C), 0.8 kg N tree^?1 (N treatment), 0.83 kg K tree^?1 (K treatment), and 0.80 kg N tree^?1 plus 0.83 kg K tree^?1 (NK treatment). During the hydrological cycle 1998/1999, only 250 mm of rain were recorded. Because of this, from 1998 to 1999 a decrease in the concentrations of mobile nutrients N, phosphorus (P), and K and an increase in calcium (Ca), iron (Fe), and manganese (Mn) were observed in leaves. The application of N led to higher leaf N concentration compared with other treatments. This response allowed the establishment of a linear model that relates soil plant analysis development (SPAD) readings with leaf N concentrations (r²=0.55; P<0.05). Compared with leaves, fruits showed similar amounts of N and P; less Ca, Mg, Fe, and Mn; and high concentrations of K. Fertilization did not change considerably the mineral composition of fruits, and because of large variation among trees, yield was similar for all treatments.     

Effects of foliar antitranspirant or calcium nitrate applications on yield and blossom‐end rot occurrence in greenhouse‐grown peppers

In order to reduce blossom‐end rot occurrence in greenhouse‐grown peppers, experiments were conducted to determine whether foliar applications of antitranspirants would decrease transpiration of pepper (Capsicum annuum L. cv. Hungarian Wax or Midal) leaves and subsequently redirect the flow of calcium (Ca) from plant foliage to developing fruit. Foliar calcium nitrate [Ca(NO₃)₂] applications were also carried out as a possible means to increase fruit Ca concentration and reduce blossom‐end rot. Initial studies indicated that two antitranspirant applications of 2.5% ‘Vapor Gard’ (di‐1‐p‐menthene) early in the fruiting phase of ‘Hungarian Wax’ peppers significantly increased early yield and tended to increase total Ca in the fruit. In subsequent experiments, weekly applications of either antitranspirant ‐ 1% ‘Vapor Gard’ or 1% ‘Folicote’ (a wax emulsion concentrate) ‐ throughout the fruiting phase significantly increased fruit Ca of ‘Midal’ peppers during at least part of the reproductive stage, and significantly reduced blossom‐end rot‐affected yield. Weekly Ca(NO₃)₂ applications significantly elevated leaf Ca as well as fruit Ca concentrations, and was the most effective treatment in alleviating blossom‐end rot. However, all weekly Ca(NO₃)₂ and antitranspirant treatments caused significant declines in marketable yield, so that these treatments, although effective in reducing blossom‐end rot, cannot be recommended for commercial use.     

Simultaneous use of plant growth promoting rhizobacterium and nitrogenous fertilizers may help in promoting growth,yield, and nutritional quality of okra

This study was conducted to evaluate the simultaneous use of plant growth promoting rhizobacterium (QS1) and different combinations of urea-nitrogen and biogas slurry-nitrogen for improving growth, yield, and nutritional quality of field grown okra. The isolate QS1 was identified as Bacillus sp. QS1 based on its ribosomal ribonucleic acid (rRNA) sequence analysis. Results revealed that among the combinations, the application of 50% urea-nitrogen + 50% biogas slurry-nitrogen was optimal for improving crop performance. This combination significantly (p ≤ 0.05) promoted okra growth viz. plant height (69.63–80.03 cm), no of branches per plant (14–18), shoot fresh weight (86.66–136.25 g/plant), root fresh weight (22.5–26.58 g/plant), and fruit yield (8.5–13.5 kg/plot) compared to the plants receiving 100% urea-nitrogen. The interactive effective of this nitrogen combination and QS1 inoculation produced the highest growth and yield response. Similarly, the same treatment improved nitrogen, phosphorus, potassium, and protein contents in shoot and fruit of okra compared to other treatments.     

COMPOSTS AS SOIL SUPPLEMENT ENHANCED PLANT GROWTH AND FRUIT QUALITY OF STRAWBERRY

ABSTRACT

Compost significantly enhanced strawberry (Fragaria × ananassa Duch.) plant growth and fruit quality when used as a soil supplement. Adding half strength of Peter nutrient solution (50% fertilizer) to a mixture of 50% soil plus 50% compost was very effective in significantly increasing plant dry weight to approximately double that of controls (without compost), fruit yield by more than 70%, and fruit size by 15% compared to controls in the two strawberry cultivars (“Allstar” and “Honeoye”). Compost and fertilizer also significantly enhanced leaf chlorophyll content. Nitrate reductase activity significantly increased in leaves and roots with the greatest increases when using 50% soil plus 50% compost. Strawberry plants grown with compost had significantly higher levels of nitrogen (N) and potassium (K), but lower levels of manganese (Mn), iron (Fe), molybdenum (Mo), and nickel (Ni) in fruit of both “Allstar” and “Honeoye”. Adding compost to the soil mix did not change zinc (Zn) and cadmium (Cd) levels. Use of compost also significantly increased levels of organic acids (malic and citric acid), sugars (fructose, glucose, and total sugars), soluble solids content, and titratable acidity content in both cultivars. The results indicate that the use of compost can reduce the amount of fertilizer required for optimum strawberry plant growth.     

Promotion of growth,yield and fiber quality attributes of Egyptian cotton by bacillus strains in combination with mineral fertilizers

Abstract

Implementation of proper management practices using biological approaches is important to maintain soil quality and cotton yield in sandy desert soils of Egypt. This experiment was conducted at the Agriculture Experimental farm, Kafer El-Sheikh governorate, Cotton Research Institute of Egypt during 2016–2017 seasons to study the effect of inoculation with bacterial strains of Bacillus circulance (BC) and Bacillus megatherium (BM) and their co-inoculation in combinations with 50% and 100% of recommended dose fertilization (RDF) on growth, yield, and fiber properties of Egyptian cotton Giza-94. Results showed that all important morphological attributes of cotton such as plant growth, number of fruit sympodial branches, number of bolls per plant, boll weight, lint cotton yield and fiber properties significantly increased with the increase rate of RDF, and inoculation of cotton seeds with the bacterial strains exerted additive effects. The highest increase of cotton yield was observed at the combined use of bacterial strains BC?+?BM with 50% RDF followed by BC?+?BM with 100% RDF treatment which attributed on the cotton yield increase by 33% and 15% compared to the respective control. The application of Bacillus strains as a biofertilizer could be an alternative option to reduce considerable amounts of chemical fertilizers input by enhancing nutrient use efficiency (NUE) and, thereby, improves cotton productivity.     

Effect of Calcium and Boron Sprays on Yield and Quality of “Elsanta” Strawberry

Abstract

The aim of the experiment was to examine the effects of foliar applications of calcium (Ca) and boron (B) on yield and fruit quality of “Elsanta” strawberries grown on a sandy loam soil with low status of available B. The study was conducted in 1999–2000 at a commercial strawberry plantation in Central Poland. Cold‐stored strawberries were planted in 1998 at a spacing of 0.25 × 0.8 m. The following treatments were applied: (i) five sprays of Ca as CaCl₂ at a rate of 1.5 kg Ca ha^?1 spray^?1 with addition of Tween 20 adjuvant at 0.1%; the first spray was performed at the petal fall stage and the next at 5‐day intervals; (ii) three sprays of B as Borvit material at a rate of 160 g B ha^?1 spray^?1 at the beginning of flowering and 5, and 10 days later; (iii) sprays of B and Ca as in the combination of (i) and (ii). Plants sprayed with water served as the control. Results showed that fruit and leaves from Ca‐treated plants had increased Ca concentrations. Sprays with B increased status of this microelement in fruit and leaf tissues. Treatments did not affect total and marketable fruit yield, mean berry weight, the number deformed fruit, soluble solids concentration and titratable acidity of fruit at harvest. Fruit sprayed with Ca or B plus Ca were firmer and more resistant to Botrytis rot at harvest and after 3 days of holding at 18°C compared to those of control plots. Moreover, sprays of Ca or B plus Ca increased soluble solids concentration and titratable acidity of fruit after 3 days of holding at room temperature. These results indicate that sprays of CaCl₂ with addition of Tween 20 should be recommended to improve quality and shelf‐life of strawberry fruit, particularly in proecological production where application of fungicides is restricted.     

Yield of iron‐sprayed and non‐sprayed strawberry cultivars grown on high ph calcareous soil

Abstract

Iron (Fe) deficiency chlorosis (FeDC) results in extensive reduction in yield of strawberry (Fragaria x ananassa Duch.) grown on high pH calcareous soils. Three cultivars differing in response to FeDC were grown on a high pH (8.2) calcareous soil (25.4% calcium carbonate equivalent in surface 20 cm) in the field (Choueifat, coastal area of Lebanon) to determine the effects of FeDC on fruit yield of cultivars sprayed with FeEDDHA [ferric ethylene‐diiminobis (2‐hydroxyphenyl) acetate]. The unsprayed plots were used as a control. No significant interaction (P<0.05) between cultivars x FeEDDHA spray treatment, and no significant differences (P<0.05) between one and two FeEDDHA spray(s)/week treatment was noted for visual FeDC, fruit number, and fruit yield. Sprayed cultivars once a week produced higher yields than unsprayed ones; overall increases were 33% (13% for ‘Motto’, 30% for ‘Chandler’, and 56% for ‘Douglas'). Even though only slight FeDC was noted on the ‘Motto’ cultivar receiving no Fe EDDHA spray, fruit yields were increased when sprayed with FeEDDHA. However, significant increases in yield for ‘Chandler’ and ‘Douglas’ cultivars with severe FeDC ratings were rioted when sprayed with FeEDDHA.     

Ameliorative Effect of Calcium Nitrate on Cucumber and Melon Plants Drip Irrigated with Saline Water

Abstract

Cucumber (Cucumis sativus cv. Orlando) and melon (Cucumis melo cv. Ananas) were field grown to investigate the effects of supplementary calcium nitrate applied to irrigation water on plant growth and fruit yield of salt stressed and unstressed cucumber and melon plants. Treatments were (1) control: normal irrigation water (C); (2) normal irrigation water plus supplementary 5 mM Ca(NO₃)₂ added to the irrigation water (C + CaN); (3) salt treatment: C plus 60 mM NaCl added irrigation water (C + S); and (4) supplementary Ca(NO₃)₂: C + S plus supplementary 5 mM Ca(NO₃)₂ added to the irrigation water (C + S + CaN). Plants irrigated with water containing high NaCl produced less dry matter, fruit yield, and chlorophyll than the control treatments of both species. Supplementing irrigation water with Ca(NO₃)₂ resulted in increases in dry matter, fruit yield, and chlorophyll concentrations over plants irrigated with saline water. Membrane permeability increased with C + S treatment for both species. Supplementary Ca(NO₃)₂ restored membrane permeability. Sodium (Na) concentration in plant tissues increased in leaves and roots in the elevated NaCl treatment. Concentrations of Ca and N in leaves were decreased in the high salt treatment and fully restored by supplementary Ca(NO₃)₂. These results clearly show that supplementary Ca(NO₃)₂ can partly mitigate the adverse effects of saline water on both fruit yield and whole plant biomass in melon and cucumber plants.     

Compositional nutrient diagnosis and main nutrient interactions in yellow pepper grown on desert calcareous soils

Mineral‐nutrient stress is one of the main factors limiting crop production, especially in arid lands. The mineral requirement of a crop is difficult to determine, and the interpretation of foliar chemistry composition is not easy. This study was conducted to compute the minimum yield target for fresh fruit of yellow pepper (Capsicum annuum L.) and the corresponding Compositional Nutrient Diagnosis (CND) as well as to identify significant nutrient interactions of this crop in desert calcareous soils. Preliminary CND norms were developed using a cumulative variance‐ratio function and the chi‐square distribution function. From a small database, we computed means and standard deviations of row‐centered log ratios, V_X, of five nutrients (N, P, K, Ca, and Mg) and a filling value, R, which comprises all nutrients not chemically analyzed and quantified them in 54 foliar samples of the popular yellow pepper cv. ‘Santa Fé’. This cultivar is widely grown in northwest Mexico under arid conditions. These norms are associated to fresh fruit yields higher than 15.04 t ha^–1. Principal‐component analyses, performed using estimated CND nutrient indexes, allowed us to identify four interactions: negative P‐Ca, P‐Mg, and N‐K, and positive Ca‐Mg. Pepper plants growing on calcareous soils tend to take up more Ca and Mg than considered as optimum in other soil conditions.     

MINERAL COMPOSITION OF STRAWBERRY,MULBERRY AND CHERRY FRUITS AT DIFFERENT RIPENING STAGES AS ANALYZED BY INDUCTIVELY COUPLED PLASMA-OPTICAL EMISSION SPECTROSCOPY

Mineral contents of strawberry (Fragaria x ananassa), mulberry (Morus alba, M. nigra, M. macroura, and M. laevigata) and cherry (Prunus avium) fruits at un-ripened, semi-ripened and fully-ripened stages were investigated. The concentrations (mg kg^?1) of potassium (K), phosphorus (P), calcium (Ca), and magnesium (Mg) in the fruits (DW), at fully-ripened stage, varied from 2600 (mulberry) to 3300 (strawberry), 1854 (cherry) to 2954 (mulberry), 1855 (cherry) to 4375 (mulberry) and 1025 (cherry) to 2225 (mulberry), respectively. Sizeable amounts (mg kg^?1) of Zn 408 (strawberry) to 1110 (mulberry) and Fe 236 (cherry) to 1080 (mulberry) were also determined. Moreover, the tested fruits contained considerable amounts of sodium (Na), manganese (Mn), aluminum (Al), and copper (Cu). Overall, the concentrations of these minerals except K were found to decrease as fruit maturity progressed. The tested fruits, especially Morus species, can be explored as a rich source of Zn and Fe, the two essential elements that are in short supply in human diet.     

Response of the soil bacterial community to the addition of toluene and toluene-degrading bacteria

Changes in soil bacterial communities after toluene and/or toluene degrading bacteria were added were monitored by growth on various media, and by the culture-independent method of Reverse Sample Genome Probing (RSGP). A total of 397 isolates that were cultured from toluene-amended and non-amended soil were identified using fatty acid methyl ester (FAME) analysis. In 75% of the soil samples, gram-positive bacteria dominated, primarily Bacillus sp. and Cellulomonas sp. In contrast, RSGP revealed Proteobacteria (α, β, and γ subgroups) to be the dominant species, with Bacillus sp. dominant in only one soil sample.In toluene-treated soil, FAME and RSGP analyses indicated that by day 5 the major bacterial populations were gram-negative bacteria, in particular, Pseudomonas sp., Acinetobacter sp., and Alcaligenes sp. When toluene and Pseudomonas putida D8 were coincidentally introduced, the proportion of Pseudomonas sp. in the bacterial population recovered using non-selective medium increased from 16 to 62% and then rapidly decreased to about 9%. When we used selective medium to monitor the population of P. putida D8, a rapid initial increase followed by a gradual decline was also observed. In samples analyzed by RSGP, D8 was one of the major species of the bacterial community at day 2, but its signal intensity dropped to 9.5% by day 5.The influence of D8 addition on the bacterial profile was monitored in growth-based examinations. Bacillus sp. and Pseudomonas sp. were initially dominant. By day 5, Bacillus sp. decreased while the Proteobacteria, (including Acinetobacter sp., Agrobacterium sp., Alcaligenes sp., Burkholderia sp., Erwinia sp., and Pseudomonas sp.) increased. At the same time, D8 decreased to a level indistinguishable from background. Conversely, RSGP analysis revealed the population dominance of P. putida (including D8) and Rhizobium fredii at day 2. Populations shifted toward Agrobacterium tumefaciens, Bacillus subtilis, R. fredii, and D8 by day 5.P. putida D8 levels could be monitored using RSGP when cultivation failed. However, cultivation of Bacillus sp. was always successful, while the organism was only occasionally detected by RSGP. While cultivation and RSGP methods comparably detected the same major bacterial populations, the overall bacterial diversity was greater with RSGP than with growth-based testing.     

Effect of plant growth-promoting bacteria and soil compaction on barley seedling growth, nutrient uptake, soil properties and rhizosphere microflora

Inoculants are of great importance in sustainable and/or organic agriculture. In the present study, plant growth of barley (Hordeum vulgare) has been studied in sterile soil inoculated with four plant growth-promoting bacteria and mineral fertilizers at three different soil bulk densities and in three harvests of plants. Three bacterial species were isolated from the rhizosphere of barley and wheat. These bacteria fixed N₂, dissolved P and significantly increased growth of barley seedlings. Available phosphate in soil was significantly increased by seed inoculation of Bacillus M-13 and Bacillus RC01. Total culturable bacteria, fungi and P-solubilizing bacteria count increased with time. Data suggest that seed inoculation of barley with Bacillus RC01, Bacillus RC02, Bacillus RC03 and Bacillus M-13 increased root weight by 16.7, 12.5, 8.9 and 12.5% as compared to the control (without bacteria inoculation and mineral fertilizers) and shoot weight by 34.7, 34.7, 28.6 and 32.7%, respectively. Bacterial inoculation gave increases of 20.3–25.7% over the control as compared with 18.9 and 35.1% total biomass weight increases by P and NP application. The concentration of N and P in soil was decreased by increasing soil compaction. In contrast to macronutrients, the concentration of Fe, Cu and Mn was lower in plants grown in the loosest soil. Soil compaction induced a limitation in root and shoot growth that was reflected by a decrease in the microbial population and activity. Our results show that bacterial population was stimulated by the decrease in soil bulk density. The results suggest that the N₂-fixing and P-solubilizing bacterial strains tested have a potential on plant growth activity of barley.     

How strawberry plants cope with limited phosphorus supply: Nursery‐crop formation and phosphorus and nitrogen uptake dynamics

Healthy, well‐rooted planting stocks are important for profitable fruit production of strawberry (Fragaria × ananassa Duch.). Adequate nutrient inputs and crop‐rotation practices are among the most important measures to insure a successful, rapid development of strawberry nursery plants. However, relationships between macronutrient use and strawberry‐nursery‐plant formation in different rotation environments are not well understood. Our objectives were to assess strawberry plant P : N nutrition and nursery development under various limited and unlimited P inputs applied at different growth stages and to examine how nursery plants cope with limited P inputs. The field studies were conducted in a wheat–ryegrass–ryegrass–strawberry (WRRS) system in 2008 and in another corn–ryegrass–ryegrass–strawberry (CRRS) system in 2009 in Nova Scotia, Canada. The nursery crop was cv. Strawberry Festival and the experimental treatments consisted of three mother‐stock P (MSP) rates (0, 6.6, and13.2 P kg ha^–1) and five daughter‐plant P (DPP) rates (0, 13.2, 26.4, 39.6, and 52.8 kg P ha^–1), representing 0%–125% of the regional recommendations for strawberry nursery. The P treatments were arranged with three blocks in a split‐plot design in each field. The results showed that the effects and interactions of the MSP and DPP treatments were significant (P < 5%) on whole‐plant P and N acquisition and nursery productivity. Two‐year whole‐plant total P and N acquisition varied between (13.2 ± 2.0) kg P ha^–1 and (46 ± 7.3) kg N ha^–1 (n = 270) in both nursery systems. There was a quadratic regression relationship between nursery runners and daughter plants with plant P and N acquisition (0.33 < R² < 0.42, P < 5%). Soil pH levels declined with time and were positively correlated with nursery‐plant formation. Too many runners (18–22 per mother stock) might reduce nursery‐plant formation. Limited P inputs (37.5%–62.5% of regular recommendation) might result in a suitable plant P : N ratio (0.12–0.13) and adequate daughter plant‐to‐runner ratios (1.4–1.7) for optimum nursery formation (14–16 daughter plants per mother stock). Nutrient P was the single controlled factor influencing the N acquisition of nursery plants. High P inputs (> 39.6 P ha^–1 or > 75% of regular recommendation) may harm the crops. Therefore, this study implies that low‐input horticulture can improve the nutrition management of strawberry nursery.