Modulation of the ROS‐scavenging system in salt‐stressed wheat plants inoculated with arbuscular mycorrhizal fungi

Although there is evidence for a positive involvement of the antioxidant defense system in plant response to salt stress, there is poor information regarding the influence of mycorrhizal symbiosis on enzymatic and nonenzymatic antioxidant defense in wheat under saline conditions. The present article focuses on the contribution of mycorrhizae to antioxidant defense in salt‐stressed wheat plants. Two wheat (Triticum aestivum L.) cultivars, Sids 1 and Giza 168, were grown under nonsaline or two saline conditions (4.7 and 9.4 dS m^–1) with and without arbuscular mycorrhizal fungi (AMF) inoculation. Salt stress considerably decreased root colonization and plant productivity, particularly in Giza 168. Interestingly, mycorrhizal colonization alleviated the adverse effect of salt stress and significantly enhanced plant productivity, especially in Sids 1. The concentration of glycinebetaine, the activities of antioxidative enzymes (superoxide dismutase, peroxidase, catalase, and glutathione reductase) and the concentrations of antioxidant molecules (glutathione and ascorbate) were increased under saline conditions; these increases were more significant in salt‐stressed mycorrhizal plants, especially in Sids 1. Salt stress induced oxidative damage through increased lipid peroxidation, electrolyte leakage, and hydrogen peroxide concentration, particularly in Giza 168. Mycorrhizal colonization altered plant physiology and significantly reduced oxidative damage. Elimination of reactive oxygen species (ROS) can be one of the mechanisms how AMF improve wheat adaptation to saline soils and increase its productivity.     

Single and double inoculation with Azospirillum/Trichoderma: the effects on dry bean and wheat

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

Effect of zinc‐biofortified seeds on grain yield of wheat,rice, and common bean grown in six countries

Seeds enriched with zinc (Zn) are ususally associated with better germination, more vigorous seedlings and higher yields. However, agronomic benefits of high‐Zn seeds were not studied under diverse agro‐climatic field conditions. This study investigated effects of low‐Zn and high‐Zn seeds (biofortified by foliar Zn fertilization of maternal plants under field conditions) of wheat (Tritcum aestivum L.), rice (Oryza sativa L.), and common bean (Phaseolus vulgaris L.) on seedling density, grain yield and grain Zn concentration in 31 field locations over two years in six countries. Experimental treatments were: (1) low‐Zn seeds and no soil Zn fertilization (control treatment), (2) low‐Zn seeds + soil Zn fertilization, and (3) Zn‐biofortified seeds and no soil Zn fertilization. The wheat experiments were established in China, India, Pakistan, and Zambia, the rice experiments in China, India and Thailand, and the common bean experiment in Brazil. When compared to the control treatment, soil Zn fertilization increased wheat grain yield in all six locations in India, two locations in Pakistan and one location in China. Zinc‐biofortified seeds also increased wheat grain yield in all four locations in Pakistan and four locations in India compared to the control treatment. Across all countries over 2 years, Zn‐biofortified wheat seeds increased plant population by 26.8% and grain yield by 5.37%. In rice, soil Zn fertilization increased paddy yield in all four locations in India and one location in Thailand. Across all countries, paddy yield increase was 8.2% by soil Zn fertilization and 5.3% by Zn‐biofortified seeds when compared to the control treatment. In common bean, soil Zn application as well as Zn‐biofortified seed increased grain yield in one location in Brazil. Effects of soil Zn fertilization and high‐Zn seed on grain Zn density were generally low. This study, at 31 field locations in six countries over two years, revealed that the seeds biofortfied with Zn enhanced crop productivity at many locations with different soil and environmental conditions. As high‐Zn grains are a by‐product of Zn biofortification, use of Zn‐enriched grains as seed in the next cropping season can contribute to enhance crop productivity in a cost‐effective manner.     

Potassium and calcium distribution patterns along the leaf insertion gradient of bean plants grown in nutrient solutions

Potassium and calcium distribution patterns along the leaf insertion gradient of bean plants (Phaseolus vulgaris L. cv Tacarigua) were analyzed in plants grown in different K and Ca concentrations in the nutrient solution. The plants were sampled at the early flowering stage and the leaves analyzed following the helix or genetic spiral which follows leaves in the order of their origin at the shoot tip. Different canopy profiles for K and Ca showed that “critical concentration limits”; could be established for K but not for Ca, due perhaps to the non‐phloem mobile nature of this element. Besides, sampling procedures based on a “representative”; leaf (or leaves) were compared to those based on the sampling of the whole canopy in order to obtain reference nutrient concentration values.     

Effect of organic amendments on uptake of selenium and biochemical grain composition of wheat and rape grown on seleniferous soils in northwestern India

Crops grown in seleniferous soil may accumulate selenium (Se) to levels considered highly toxic for animal and human consumption. Furthermore, higher Se content in plant tissues leads to considerable deterioration in product quality. Application of organic amendments plays an important role in improving soil physical, chemical, and biological conditions and influencing nutrient availability. A field trial was conducted to evaluate the effect of organic amendments, namely poultry manure (PM), sugar cane press mud (SCPM), and farmyard manure (FYM), on Se uptake and grain quality of wheat and oilseed rape grown on a seleniferous soil in Punjab, India. Selenium accumulation by wheat and oilseed rape grains decreased significantly (75%–95%) with the application of PM and SCPM, while FYM application resulted in a significant decrease (23%) only in case of wheat grains. The amount of Se associated with seed proteins varied in proportion to its uptake under different treatments. Quality of wheat grains improved considerably with respect to total soluble sugars, reducing sugars, starch, lipids, and sulfur concentrations only after application of SCPM and PM. Treating a Se‐contaminated soil with organic amendments significantly increased the oil concentration and changed the proportion of various fatty acids in rape grains. It is concluded that applying organic amendments to Se‐contaminated soils can alleviate the deleterious effects of Se and restore the nutritional quality of grains.     

Selection and characterization of wheat genotypes for saline soils prone to water‐logging

Wheat (Tritcum aestivum L.) genotypes were screened and characterized for performance under salt stress and/or water‐logging. In a solution‐culture study, ten wheat genotypes were tested under control, 200 mM–NaCl salt stress and 4‐week water‐logging (nonaerated solution stagnated with 0.1% agar), alone or in combination. Shoot and root growth of the wheat genotypes was reduced by salinity and salinity × water‐logging, which was associated with increased leaf Na⁺ and Cl^– concentrations as well as decreased leaf K⁺ concentration and K⁺ : Na⁺ ratio. The genotypes differed significantly for their growth and leaf ionic composition. The genotypes Aqaab and MH‐97 were selected as salinity×water‐logging‐resistant and sensitive wheat genotypes, respectively, on the basis of their shoot fresh weights in the salinity × water‐logging treatment relative to control. In a soil experiment, the effect of water‐logging was tested for these two genotypes under nonsaline (EC = 2.6 dS m^–1) and saline (EC = 15 dS m^–1) soil conditions. The water‐logging was imposed for a period of 21 d at various growth stages, i.e., tillering, stem elongation, booting, and grain filling alone or in combinations. The maximum reduction in grain yield was observed after water‐logging at stem‐elongation + grain‐filling stages followed by water‐logging at grain‐filling stage, booting stage, and stem‐elongation stage, respectively. Salinity intensified the effect of water‐logging at all the growth stages. It is concluded that the existing genetic variation in wheat for salinity × water‐logging resistance can be successfully explored using relative shoot fresh weight as a selection criterion in nonaerated 0.1% agar–containing nutrient solution and that irrigation in the field should be scheduled to avoid temporary water‐logging at the sensitive stages of wheat growth.     

Potassium efficiency mechanisms of wheat,barley, and sugar beet grown on a K fixing soil under controlled conditions

Plant species differ in their potassium (K) efficiency, but the mechanisms are not clearly documented and understood. Therefore, K efficiency of spring wheat, spring barley, and sugar beet was studied under controlled conditions on a K fixing sandy clay loam. The effect of four K concentrations in soil solution ranging from low (5 and 20 μM K) to high (2.65 and 10 mM K) on plant growth and K uptake was investigated at 3 harvest dates (14, 21, and 31 days after sowing). The following parameters were determined: shoot dry matter (DM), K concentration in shoot dry matter, root length (RL), root length/shoot weight ratio (RSR), shoot growth rate/average root length ratio (GR_s/aRL), K influx, and soil solution K concentrations. Wheat proved to have a higher agronomic K efficiency than barley and sugar beet, indicated by a greater relative yield under K‐deficient conditions. As compared to both cereals, sugar beet was characterized by higher K concentrations in the shoot dry matter, only 30—50 % of the root length, 15—30 % of the RSR and a 3 to 6 times higher GR_s/aRL. This means that the shoot of sugar beet had a 3 to 6 times higher K demand per unit root length. Even at low K concentrations in the soil solution, sugar beet had a 7 to 10 times higher K influx than the cereals, indicating that sugar beet was more effective in removing low available soil K. Wheat and barley were characterized by slow shoot growth, low internal K requirement, i.e. high K utilization efficiency, and high RSR, resulting in a low K demand per unit root length. At low soil K concentrations, both cereals increased K influx with age, an indication of adaptation to K deficiency. The mechanism of this adaptation merits closer investigation. Model calculations were performed to estimate the K concentration difference between the bulk soil and the root surface (ΔC_L) needed to drive the measured K influx. For the two cereals, the calculated ΔC_L was smaller than the K concentration in the soil solution, but for sugar beet, ΔC_L was up to seven times higher. This indicates that sugar beet was able to mobilize K in the rhizosphere, but the mechanisms responsible for this mobilization remain to be studied.     

Response of photosynthetic active radiation interception,dry matter accumulation,and grain yield to tillage in two winter wheat genotypes

ABSTRACT

To examine the effects of winter wheat genotypes on dry matter (DM) accumulation and grain yield (GY) under no-tillage conditions in North China Plain (NCP), a field experiment was conducted using the genotypes Tainong 18 (F) and Jimai 22 (J). Two tillage systems were tested, conventional tillage (CT) and no-tillage (NT) during the 2015/2016 and 2016/2017 winter wheat growing seasons. Genotypes and tillage systems were compared regarding DM accumulation, GY, leaf area index (LAI), photosynthetic active radiation (PAR) interception, and flag leaf fluorescence parameters. LAI, PAR interceptions, and flag leaf fluorescence parameters were significantly higher under CT than under NT conditions. This suggests that the efficiency of light harvesting by the PSII reaction center of leaves can increase due to CT. DM accumulation was significantly higher under CT than under NT. Spike DM accumulation was higher in F than in J in the heading and the filling stages. In both growing seasons, GY was significantly higher under CT than under NT, GY of NTF was significantly higher than that of NTJ, which was due to a significantly higher number of kernels per spike. This indicates that genotype F can compensate for a low GY due to NT.     

Inoculation with phosphate-solubilizing microorganisms and a vesicular-arbuscular mycorrhizal fungus improves dry matter yield and nutrient uptake by wheat grown in a sandy soil

 The effect of inoculating wheat (Triticum aestivum L.) with the PO₄ ^3–-solubilizing microorganisms (PSM) Bacillus circulans and Cladosporium herbarum and the vesicular-arbuscular mycorrhizal (VAM) fungus Glomus sp. 88 with or without Mussoorie rock phosphate (MRP) amendment in a nutrient-deficient natural sandy soil was studied. In the sandy soil of low fertility root colonization by VAM fungi was low. Inoculation with Glomus sp. 88 improved root colonization. At maturity, grain and straw yields as well as N and P uptake improved significantly following inoculation with PSM or the VAM fungus. These increases were higher on combined inoculation of PSM and the VAM fungus with MRP amendment. In general, a larger population of PSM was maintained in the rhizosphere of wheat in treatments with VAM fungal inoculation and MRP amendment. The results suggest that combined inoculation with PSM and a VAM fungus along with MRP amendment can improve crop yields in nutrient-deficient soils. Received: 4 September 1997     

Perturbation of nutrient source–sink relationships by post‐anthesis stresses results in differential accumulation of nutrients in wheat grain

Mineral nutrients in grains act as a source of nutrients in human diets, in which deficiencies of key minerals including calcium, magnesium, copper, iron, and zinc have prompted efforts to increase their concentrations in the edible portions of staple grain crops. Wheat (Triticum aestivum L.) crops in many regions often suffer abiotic stresses such as drought, extreme heat or frost during grain filling, which affect mineral source–sink relationships. We hypothesized that these stresses would have nutrient‐specific impacts on grain nutrient concentrations due to differences among nutrients in phloem mobility, post‐anthesis uptake and grain loading patterns. Nutrient loading patterns into wheat grains were investigated in two wheat cultivars in the field by sequentially harvesting tagged ears and analyzing tissues for key nutrients. In addition, the impact of perturbed source–sink relations during grain filling on nutrient loading was investigated by inducing post‐anthesis drought /floret abortion in a glasshouse study. Over 90% of Ca and around 70% of Na, K, and Mg accumulated in both wheat cultivars in the field during the first 14 d of grain development. The concentrations of micronutrients (Mn, Fe, Cu and Zn), Mg and P in grains generally increased when florets were aborted, and were unchanged under drought stress, while concentrations of Ca and K were highest under drought stress and lowest under the 66% floret abortion treatment. The observed changes in grain nutrient concentrations from post‐anthesis drought/floret abortion could not be fully explained by nutrient‐specific differences in phloem mobility, post‐anthesis uptake and grain loading patterns. This study will inform future research to define the precise roles of individual nutrients within developing grains and to fully understand the observed variations in grain nutrient concentrations due to source/sink modifications.     

Salt‐resistant and salt‐sensitive wheat genotypes show similar biochemical reaction at protein level in the first phase of salt stress

Salinity has a two‐phase effect on plant growth, an osmotic effect due to salts in the outside solution and ion toxicity in a second phase due to salt build‐up in transpiring leaves. To elucidate salt‐resistance mechanisms in the first phase of salt stress, we studied the biochemical reaction of salt‐resistant and salt‐sensitive wheat (Triticum aestivum L.) genotypes at protein level after 10 d exposure to 125 mM–NaCl salinity (first phase of salt stress) and the variation of salt resistance among the genotypes after 30 d exposure to 125 mM–NaCl salinity (second phase of salt stress) in solution culture experiments in a growth chamber. The three genotypes differed significantly in absolute and relative shoot and root dry weights after 30 d exposure to NaCl salinity. SARC‐1 produced the maximum and 7‐Cerros the minimum shoot dry weights under salinity relative to control. A highly significant negative correlation (r² = –0.99) was observed between salt resistance (% shoot dry weight under salinity relative to control) and shoot Na⁺ concentration of the wheat genotypes studied. However, the salt‐resistant and salt‐sensitive genotypes showed a similar biochemical reaction at the level of proteins after 10 d exposure to 125 mM NaCl. In both genotypes, the expression of more than 50% proteins was changed, but the difference between the genotypes in various categories of protein change (up‐regulated, down‐regulated, disappeared, and new‐appeared) was only 1%–8%. It is concluded that the initial biochemical reaction to salinity at protein level in wheat is an unspecific response and not a specific adaptation to salinity.     

Impact of plant genotype and nitrogen level on rice growth response to inoculation with Azospirillum sp. strain B510 under paddy field conditions

Abstract

Twenty rice cultivars, including three genetically-distinct groups (japonica, indica-1, and indica-2), were evaluated for their response to inoculation with Azospirillum sp. strain B510 in paddy fields with standard nitrogen (SN) and low nitrogen (LN) fertilization. In the SN field, the tiller numbers in most indica-2 cultivars, 37?days after transplanting (DAT), were significantly increased by the B510 inoculation, whereas those in 4 japonica cultivars were significantly decreased. A similar growth response was observed in the LN field, although the impacts of the B510 inoculation were more varied than in the SN field. At 58 DAT, the tiller numbers in most cultivars were lower or unaffected by the B510 inoculation under both SN and LN conditions, except that the tiller number of the Nipponbare cultivar, which is classified as japonica, was significantly higher in the LN field only. These results suggest that the effects of inoculation with Azospirillum sp. strain B510 on the growth of rice plants, especially on tiller numbers at the early growth stage, vary depending on the rice genotype, as well as nitrogen level. Therefore, the plant genotypes, growth stages, and fertilization managements must be considered when a plant-associated bacterium is evaluated for beneficial effects under field conditions.     

Varietal tolerance to Zinc deficiency in wheat and barley grown in chelatorbuffered nutrient solution and its effect on uptake of Cu,Fe, and Mn

Tolerance to zinc (Zn) deficiency was examined for three wheat (Triticum aestivum L.) and three barley (Hordeum vulgare L.) varieties grown in chelator‐buffered nutrient solution. Four indices were chosen to characterize tolerance to Zn deficiency: (1) relative shoot weight at low compared to high Zn supply (“Zn efficiency index”), (2) relative shoot to root ratio at low compared to high Zn supply, (3) total shoot uptake of Zn under deficient conditions, and (4) shoot dry weight under deficient conditions. Barley and wheat exhibited different tolerance to Zn deficiency, with barley being consistently more tolerant than wheat as assessed by all four indices. The tolerance to Zn deficiency in the barley varieties was in the order Thule=Tyra>Kinnan, and that of wheat in the order Bastian=Avle>Vinjett. The less tolerant varieties of both species accumulated more P in the shoots than the more tolerant varieties. For all varieties, the concentrations of Mn, Fe, Cu, and P in shoot tissue were negatively correlated with Zn supply. This antagonism was more pronounced for Mn and P than for Cu and Fe. Accumulation of Cu in barley roots was extremely high under Zn‐deficient conditions, an effect not so clearly indicated in wheat.     

Plant‐growth‐promoting rhizobacteria isolated from a Calcisol in a semi‐arid region of Uzbekistan: biochemical characterization and effectiveness

Bacteria were isolated from the rhizosphere of cotton, wheat, alfalfa, and tomato grown in field locations within a semi‐arid region of Uzbekistan. Strains were identified as Pseudomonas denitrificans, P. rathonis, Bacillus laevolacticus, Bacillus amyloliquefaciens, and Arthrobacter simplex. The isolated strains produced different enzymes, phytohormone auxin and were antagonists against specific plant‐pathogenic fungi. Most of the strains are tolerant with respect to salt and temperature. All of the bacterial strains isolated in this study have been found to increase plant growth of wheat and maize in pot experiments.     

Synergistic effect of inoculating plant growth-promoting Pseudomonas spp. and Rhizobium leguminosarum-FB1 on growth and nutrient uptake of rajmash (Phaseolus vulgaris L.)

Plant growth-promoting bacteria (PGPB) Pseudomonas lurida-NPRp15 and Pseudomonas putida-PGRs4 possessing multiple plant growth-promoting traits were isolated from rhizoplane of pea and rhizosphere of garlic, respectively. The effects of individuals and combinations of Pseudomonas spp. with effective root nodulating symbiotic nitrogen fixing Rhizobium leguminosarum-FB1 on plant growth, nutrient uptake and yield of the rajmash plant were studied under greenhouse conditions. Bacterial inoculation resulted in significantly higher values for plant dry biomass, N, P, K, Zn and Fe contents as compared to the uninoculated control. Furthermore, dual inoculation of P. lurida-NPRp15 with R. leguminosarum-FB1 significantly increased root and shoot dry weight, nodulation, nutrient uptake, pod yield, and nutrient content of pods of rajmash VL63 compared to controls, single and triple inoculation. The results of the study indicate the potential of harnessing the benefit of plant growth-promoting and nitrogen-fixing microorganisms to improve the growth and yield of rajmash.     

Effects of NPK source on the dry matter partitioning in cool season C3-cereals (wheat,rye, barley,and oats) at various growth stages

Dry matter (DM) partitioning into root, leaf, stem, shoot dry weight plant^?1 response in four cool season C₃-cereals viz. wheat (Triticum aestivum L.), rye (Secale cereale L.), barley (Hordeum vulgare L.) and oats (Avena sativa L.) was investigated at 30, 60 and 90 days after emergence (DAE) under eight nitrogen, phosphorus and potassium (NPK) sources: S₁ = 20-20-20, S₂ = 20-27-5, S₃ = 7-22-8, S₄ = 10-10-10-20S, S₅ = 11-15-11, S₆ = 31-11-11, S₇ = 24-8-16, and S₈ = 19-6-12 in pot experiment at Dryland Agriculture Institute, West Texas A&;M University, Canyon, Texas, USA during winter 2009-10. A considerable variation in DM partitioning into various plant parts was observed in the four crop species at different growth stages and NPK source. At 30 DAE, 27% of the total DM per plant (TDMPP) was partitioned into roots and 73% into shoots (19% stems + 54% leaf). Only16 % of the TDMPP was partitioned into roots and 84% into shoots (18 % stem + 66 % leaf) at 60 DAE. At 90 DAE, 29% of TDMPP was partitioned into roots and 71 % into shoots (33 % stems + 38 % leaf) at 90 DAE. Percent DM partitioning into stems ranked first (33%) at 90 DAE > at 30 DAE (19%) > at 60 DAE (18 %). With advancement in crops age, DM partitioning into various crop parts increased. The root DM plant^?1 (RDMPP) increased from 11.5–722 mg plant^?1; stem DM plant^?1 (STDMPP) from 8.3–889.0 mg plant^?1; leaf DM plant^?1 (LDMPP) from 23.1–1031.0 mg plant^?1; shoot DM plant^?1 (SHDMPP) from 31.3–1921 mg plant^?1, and TDMPP increased from 42.9–2693.0 mg plant^?1 at 30 and 90 DAE, respectively. Because of the higher N contents in S₇ (24:8:16) and S₆ (31:11:11) reduced the DM partitioning into various plants parts as well as TDMPP at all three growth stages. The adverse effects of S₆ and S₇ on DM partitioning was more on oats > rye > wheat > barley. The S₄ with 10:10:10 (NPK) and :20S was not toxic at 30 DAE, but at 60 and 90 DAE it became toxic that adversely affected the DM partitioning as well as TDMPP probably may be due its high sulfur (20%) content which lacking in other NPK sources. The DM partitioning to various parts of barley and wheat was more than oats and rye at different growth stages (barley > wheat > rye > oats). Since the DM portioning values were determined on the average of five plants in pot experiment under organic soil at field capacity; in case of field experiments more research is needed on various crop species/varieties under different environmental conditions particularly under moisture stress condition.     

Yield response of spring wheat cultivars (Triticum aestivum and T. turgidum) to inoculation with Azospirillum brasilense under field conditions

Summary Eight commercial Israeli spring wheat cultivars (six Triticum aestivum and two T. turgidum) grown with 40 and 120 kg N/ha were tested for responses to inoculation with Azospirillum brasilense. At the low level of N fertilization (40 kg/ha), five cultivars showed significant increases in plant dry weight measured at the milky ripe stage; however, by maturation only the cultivar Miriam showed a significant increase in grain yield. Two cultivars, which had shown a positive inoculation effect at the earlier stages, had a significant decrease in grain yield. No significant effect of inoculation was found at the high N level. To confirm those results, four wheat (T. aestivum) cultivars were tested separately over 4 years in 4 different locations under varying N levels. Only Miriam showed a consistently positive effect of Azospirillum inoculation on grain yield. Inoculation increased the number of roots per plant on Miriam compared with uninoculated plants. This effect was found at all N levels. Nutrient (N, P and K) accumulation and number of fertile tillers per unit area were also enhanced by Azospirillum, but these parameters were greatly affected by the level of applied N. It is suggested that the positive response of the spring wheat cultivar Miriam to Azospirillum inoculation is due to its capacity to escape water stresses at the end of the growth season.     

Synergistic effects of the inoculation with nitrogen‐fixing and phosphate‐solubilizing rhizobacteria on the performance of field‐grown chickpea

The synergistic effects of nitrogen‐fixing and phosphate‐solubilizing rhizobacteria on plant growth, yield, grain protein, and nutrient uptake of chickpea plants were determined in a sandy clay‐loam soil. Legume grain yield and concentration and uptake of nitrogen (N) and phosphorus (P) were significantly increased as a result of co‐inoculation with Mesorhizobium and P‐solubilizing Pseudomonas and Bacillus spp. The inoculation with M. ciceri RC4 + A. chroococuum A10 + Bacillus PSB9 tripled the seed yield and resulted in highest grain protein (295 mg g^–1) at 145 d after sowing (DAS). An 8% increase in P concentration above the uninoculated control was observed in case of a single inoculation with Pseudomonas PSB 5, while the P uptake was highest (2.14‐fold above the uninoculated control) with a combined inoculation with [M. ciceri RC4 + A. chroococcum A10 + Bacillus PSB 9] at 145 DAS. The highest N concentration and N uptake at 145 DAS (81% and 16% above the uninoculated control, respectively) were observed with the triple inoculation of [M. ciceri RC4 + A. chroococcum A10 + Pseudomonas PSB 5). These findings show that multiple inoculations with rhizospheric microorganisms can promote plant growth and grain yield and increase concentrations and uptake of N and P by field‐grown chickpea.     

Effects of Single and Combined Inoculations with Azospirillum brasilense and Trichoderma harzianum on Seedling Growth or Yield Parameters of Wheat (Triticum vulgaris L., Giza 168) and Corn (Zea mays L., Hybrid 310)

Inoculation of wheat and corn grains with formulations of Azospirillum brasilense significantly increased seedling growth parameters of wheat and corn compared to untreated controls. Inoculation with Azospirillum and supplemental Trichoderma harzianum free or coimmobilized in calcium alginate resulted in significant increase in all plant growth parameters in addition to improving plant nutrient-content [phosphorus (P), potassium (K), and calcium (Ca)]. Grain treatments with T. harzianum alone or in a combination with A. brasilense were protected from invasion by Fusarium in a pot experiment. Nitrogen (N) fixation was investigated by A. brasilense free or double inoculated with T. harzianum in soil amended with different C-sources; also, phosphate solubilization was tested by these two organisms. Single and double inoculation with A. brasilense and/or T. harzianum improved wheat yield growth parameters in addition to seed protein; therefore, immobilized and coimmobilized formulations could be used as biofertilizer and biopesticide, and might be recommended to avoid the extensive use of the agrochemicals.