Mycorrhizae,biocides, and biocontrol. 4. Response of a mixed culture of arbuscular mycorrhizal fungi and host plant to three fungicides

The effects of three commonly used fungicides on the colonization and sporulation by a mixture of three arbuscular mycorrhizal (AM) fungi consisting of Glomus etunicatum (Becker & Gerd.), Glomus mosseae (Nicol. & Gerd.) Gerd. & Trappe, and Gigaspora rosea (Nicol. & Schenck) in symbiosis with pea plants and the resulting response of the host-plant were examined. Benomyl, PCNB, and captan were applied as soil drenches at a rate of 20 mg active ingredient kg^-1 soil 2 weeks after transplanting pea seedlings in a silty clay-loam soil containing the mixed inocula of AM fungi (AM plants). Effects of fungicides were compared to untreated plants that were inoculated with fungi (AM control). The effect of mycorrhizal inoculation on plant growth was also examined by including nonmycorrhizal, non-fungicide-treated plants (non-AM control). Fungicides or inoculation with AM fungi had only a small effect on the final shoot weights of pea plants, but had greater effects on root length and seed yield. AM control plants had higher seed yields and lower root lengths than the corresponding non-AM plants, and the fungicide-treated AM plants had intermediate yields and root lengths. Seed N and P contents were likewise highest in AM control plants, lowest in non-AM plants, and intermediate in fungicide-treated AM plants. All three fungicides depressed the proportion (%) of root length colonized by AM fungi, but these differences did not translate to reductions in the total root length that was colonized, since roots were longer in the fungicide-treated AM plants. Pea plants apparently compensated for the reduction in AM-fungal metabolism due to fungicides by increasing root growth. Fungicides affected the population of the three fungi as determined by sporulation at the final harvest. Captan significantly reduced the number, relative abundance, and relative volume of G. rosea spores in the final population relative to the controls. The relative volume of G. etunicatum spores was greater in all the fungicide-treated soils, while G. mosseae relative volumes were only greater in the captan-treated soil. These findings show that fungicides can alter the species composition of an AM-fungal community. The results also show that AM fungi can increase seed yield without enhancing the vegetative shoot growth of host plants.     

Impact of arbuscular mycorrhizal fungi on the growth and expression of gene encoding stress protein – metallothionein BnMT2 in the non‐host crop Brassica napus L.

Arbuscular mycorrhizal (AM) fungi are an important component of the soil biota in most agroecosystems, and their association can directly or indirectly affect the diversity of soil microorganisms, nutrient cycling, and growth of host plants. Since not all crops are symbiotic, we hypothesized that the presence of AM fungi can: (1) inhibit the growth of non‐host plants by resulting in biotic stress, or (2) promote their growth indirectly by increased nutrient mobilization. These hypotheses were tested in the present study on the non‐mycorrhizal crop canola (Brassica napus L.) in the presence and absence of other autochthonous soil microorganisms. The soil was inoculated with a mixture of AM fungi (Acaulospora longula, Glomus geosporum, G. mosseae, Scutellospora calospora) and as a control, a non‐inoculated soil was used. The impact of inoculation on plant growth (biomass production, nutrient concentrations) and expression of the stress protein metallothionein gene BnMT2 was investigated in the shoots. B. napus L. did not form mycorrhizal associations on its roots, but its growth was promoted after inoculation with AM fungi. In the soil with autochthonic microorganisms, growth inhibition after inoculation was observed compared to the control. The concentrations of N, P, K, and S in the shoot were always significantly increased after inoculation with AM fungi. However, this was partly combined with reduced growth and thereby decreased total uptake of nutrients. Expression of BnMT2 in the leaves was increased after inoculation with AM spores at the soil devoid of indigenous microorganisms, but decreased in their presence. The expression of stress proteins (BnMT2) significantly increased with increasing length and biomass of shoots. In conclusion, the inhibition of the non‐host plant B. napus L. following inoculation with AM fungi was confirmed, however, only in combination with autochthonous microorganisms. Growth promotion of B. napus L. in the presence of AM fungi in the absence of autochthonous soil microorganisms suggest that plant growth depression in the presence of AM fungi was based on interactive effects of AM fungi with the autochthonous microorganisms in the soil rather than on a direct impact of the AM fungi.     

Accumulation of Copper,Lead, and Zinc by In Situ Plants Inoculated with AM Fungi in Multicontaminated Soil

Pot and field experiments were conducted to (1) evaluate bioavailability of copper (Cu), lead (Pb), and zinc (Zn) in contaminated soil and phytoremediation potential by in situ plants, B. pilosa var. radiate and Passiflora foetida var. hispida, as inoculated with arbuscular mycorrhizal (AM) fungi, and (2) compare the results of pot and field experiments. The B. pilosa var. radiate plant inoculated with AM fungi had significantly greater Cu concentrations in the shoots and roots than noninoculated plants. Passiflora foetida var. hispida plant inoculated with AM fungi also had significantly greater Cu and Pb concentrations in the roots than noninoculated plants. As the root dry weight of Passiflora foetida var. hispida inoculated with AM fungi dramatically increased, the root Cu, Pb, and Zn content of Passiflora foetida var. hispida inoculated with AM fungi increased by 9–14 times, as compared with the noninoculated plants. The AM fungi have potential to either promote plant growth or increase heavy‐metal accumulation. The values of element translocation proportion from root to shoot were Zn > Cu > Pb for both plant species in pot and field experiments. For both plant species, the results of the pot and field experiments were significantly different. The concentration values of the pot experiment were greater in comparison to the field experiment, and some values were significantly greater than those in the field experiment.     

Differential responses of soybean and dry bean to zinc deficiency 1

Whether a legume obtains its nitrogen (N) from the air, through dinitrogen fixation, or from the soil, as nitrate (NO₃), may influence its susceptibility to zinc (Zn) deficiency. The influence of N source [potassium nitrate (KNO₃)+ native soil N versus rhizobium‐inoculated seed + native soil N] and phosphorus (P) (0 and 200 mg P/kg), and Zn fertilizers (0, 1, and 8 mg Zn/kg) on growth and nutrient composition of soybean (Glycine max L. cv. McCall) and navy bean (Phaseolus vulgaris L. cv. Seafarer) grown on a calcareous soil were studied under greenhouse conditions. Inoculated plants, but not their KNO₃‐treated counterparts, had root nodules. However, due to N deficiency resulting from suboptimal N fixation, growth of these inoculated plants, especially of navy bean, was poorer than that of similarly treated KNO₃‐fed plants. As a consequence of this restricted growth, responses to P and Zn fertilizers were generally greater in KNO₃‐treated plants. Added P decreased the yield of KNO₃‐treated navy bean in the absence of added Zn, but P‐induced Zn deficiency had little effect on the growth of similarly treated inoculated plants. Plant excess bases (EB)/total plant N ratios [EB = 1/2 Ca + l/2Mg + Na + K ‐ Cl ‐ total S (S = divalent) ‐ total P (P = monovalent)] were less in KNO₃‐treated soybean than in correspondingly treated navy bean. Therefore, rhizosphere pH values around navy bean roots were probably less than those around soybean roots. Despite the hypothesized lower rhizosphere pH values, KNO₃‐treated navy bean was more susceptible to Zn deficiency than soybean. This greater susceptibility of navy bean to Zn deficiency was apparently at least partly due to poor translocation of Zn from the roots to the tops.     

Effect of mixing soil saprophytic fungi with organic residues on the response of Solanum lycopersicum to arbuscular mycorrhizal fungi

The effect of the dual inoculation with arbuscular mycorrhizal (AM) and saprophytic fungi and a combination of wheat straw and sewage sludge residues were studied by determining their effect on dry weight of tomato and on chemical and biochemical properties of soil. Incubation of organic residue (sewage sludge combined with wheat straw) with saprophytic fungi and plant inoculation with mycorrhizal fungi was essential to study plant growth promotion. Soil application of organic residues increased the dry weight of tomato inoculated with Rhizophagus irregularis. The greatest shoot dry mass was obtained when the organic residues were incubated with Trichoderma harzianum and applied to AM plants. However, the greatest percentage of root length colonized with AM in the presence of the organic residues was obtained with inoculation with Coriolopsis rigida. The relative chlorophyll was greatest in mycorrhizal plants regardless of the presence of either saprophytic fungus. The presence of the saprophytic fungi increased soil pH as the incubation time increased. Soil nitrogen and phosphorus contents and acid phosphatase were stimulated by the addition of organic residues, and contents of N and P. Total N and P content in soil increased when the organic residue was incubated with saprobe fungi, but this effect decreased as the incubation period of the residue with saprobe fungi increased. The same trend was observed for soil β‐glucosidase and fluorescein diacetate activities. The application of organic residues in the presence of AM and saprophytic fungi seems to be an interesting option as a biofertilizer to improve plant growth and biochemical parameters of soils.     

Effects of hexachlorocyclohexane on rhizosphere fungal propagules and root colonization by arbuscular mycorrhizal fungi in Plantago lanceolata

Lindane ( γ‐hexachlorocyclohexane or γ‐HCH) is an organochlorine insecticide previously used extensively for the control of agricultural pests. We studied the effects of soil HCH contamination on vegetation and its associated arbuscular mycorrhizas (AM). The polluted and unpolluted plots had similar plant cover, with the same species richness and abundance. Plantago lanceolata plants were selected for mycorrhizal analysis because of their presence in both plots and known mycotrophy. The presence of HCH appeared to have no significant effect on the extent of colonization of Plantago roots by AM, suggesting a similar functionality of the fungal symbionts. However, infective AM propagules, the density of AM spores and viable AM hyphae in the rhizosphere were much less in the HCH‐polluted soil than in the unpolluted plot. Pre‐inoculation of four plant species with an isolate of Glomus deserticola obtained from the HCH‐contaminated soil resulted in increased growth and fungal colonization of roots compared with plants pre‐inoculated with the introduced fungus G. macrocarpum or colonized by the consortium of indigenous AM fungal species, when those plants were transplanted to an HCH‐contaminated soil. This suggests that the fungus increases the tolerance of plants to the toxic soil environment. We conclude that herbaceous and woody plants can grow in soil with little P contaminated with <100 mg HCH kg^?1 with the help of tolerant AM, despite the detrimental effect of HCH on AM fungal propagules in soil. The effects of AM fungi on plant growth and soil microbial community structure in HCH‐polluted sites could be important for remediation of the pollutant through the microbial activity in the rhizosphere.     

Influence of phosphorus application on growth,yield and oil quality of linola

Influence of different phosphorus (P) sources on growth, yield and oil quality of linola was evaluated when randomized in complete block design using three replications. Treatments were control (No P), hydropriming, soil phosphorus (50 kg ha^?1), seed inoculation with phosphate solubilizing bacteria (PSB, Bacillus spp.) and seed priming with single super phosphate (2%) alone and combined with reduced soil phosphorus (25 kg P ha^?1). Among treatments, hydropriming and seed inoculation reduced seedling 50% and mean emergence time with highest emergence index, seedling fresh and dry weights and chlorophyll contents. Seed inoculation with soil P (25 kg ha^?1) produced highest seeds per capsule, 100-seed weight, seed and biological yield, harvest index. Maximum oil percentage, low protein contents and high cost benefit ratio with net economic returns were also found for seed inoculation combined with soil phosphorus. Nonetheless, soil phosphorus application can be reduced when seed inoculation with PSB is employed.     

Mycorrhizal fungi effects on nutrient composition and yield of soybean seeds

Nutrient composition and yield of soybean [Glycine max (L.) Merr] seeds are heritable traits affected by environmental factors. This study determined the effects of arbuscular‐mycorrhizal (AM) fungi on seed protein, lipid, and phosphorus (P) composition and yield in soybean grown under a high nitrogen (N) regime. Plants were grown in pot cultures without AM fungi in P‐fertilized (+P) or unfertilized (‐P) soil, or in ‐P soil inoculated with one of the AM fungi Glomus mosseae (Nicol. & Gerd.) Gerd, and Trappe (Gm), Glomus etunicatum Becker and Gerd.(Ge), or Gigaspora rosea Nicol. and Schenck (Gr). Seed yields of+AM plants, as a group, were halfway between those of the +P and ‐P plants. Seed size was highest in Gm plants. Differences in protein concentrations between Ge and Gr and the other treatments were highly significant. Seed P and protein concentrations were not significantly correlated (p=0.162), but a highly significant (r =‐0.949) negative correlation between seed P and lipid concentrations was observed. Phosphorus concentration was highest and that of lipids lowest in +AM plants. Seed yield and nutrient composition were independent of the intensity of root colonization. The seed protein/lipid ratio was highly correlated with seed P concentration and was significantly higher for +AM plants, as a group, than for both +P and ‐P ‐AM plants. Differences in seed dry weight, size, seed/ stem ratio, P content, and protein concentration among +AM plants showed mycorrhiza‐specific host responses. These responses suggest that AM fungi can modify soybean seed development and chemical composition.     

Establishment of Retama sphaerocarpa L. seedlings on a degraded semiarid soil as influenced by mycorrhizal inoculation and sewage‐sludge amendment

A field experiment was carried out to evaluate the effectiveness of mycorrhizal inoculation with three arbuscular mycorrhizal (AM) fungi (Glomus intraradices Schenck & Smith, Glomus deserticola (Trappe, Bloss. & Menge), and Glomus mosseae (Nicol & Gerd.) Gerd. & Trappe) and the addition of composted sewage sludge (SS) with respect to the establishment of Retama sphaerocarpa L. seedlings, in a semiarid Mediterranean area. Associated changes in soil chemical (nutrient content and labile carbon fractions), biochemical (enzyme activities), and physical (aggregate stability) parameters were observed. Six months after planting, both the addition of composted SS and the mycorrhizal‐inoculation treatments had increased total N content, available‐P content, and aggregate stability of the soil. Values of water‐soluble C and water‐soluble carbohydrates were increased only in the mycorrhizal‐inoculation treatments. Rhizosphere soil from the mycorrhizal‐inoculation treatments had significantly higher enzyme activities (dehydrogenase, protease‐BAA, acid phosphatase, and β‐glucosidase) than the control soil. In the short‐term, mycorrhizal inoculation with AM fungi was the most effective treatment for enhancement of shoot biomass, particularly with G. mosseae (about 146% higher with respect to control plants). The addition of the composted SS alone was sufficient to restore soil structural stability but was not effective with respect to improving the performance of R. sphaerocarpa plants.     

Micronutrient composition of field‐grown dry bean and wheat inoculated with Azospirillum and Trichoderma

Micronutrient deficiency and malnutrition in humans are severe problems in many developing countries, particularly in areas with calcareous soils. There is almost no information on whether inoculation with plant growth–promoting Azospirillum and/or Trichoderma can help to reduce this problem by increasing the mineral concentration of the seeds. Field experiments were conducted in Tokat (Turkey) in 2001–2002 to determine whether inoculation with Azospirillum brasilense, Trichoderma harzianum, sole or in combination, and/or the application of P fertilizers can enhance micronutrient concentrations of field‐grown bean (Phaseolus vulgaris) and wheat (Triticum aestivum). In beans, Azospirillum inoculation combined with P fertilization significantly (p < 0.05) increased seed concentrations of Mn, Zn, and Cu, from 8.8, 22.6, and 7.0 mg kg^–1 in the control to 10.3, 28.3, and 11.0 mg kg^–1, respectively. Trichoderma inoculation alone significantly (p < 0.05) reduced the concentrations of Fe, Mn, Zn, and Cu and the cumulative plant uptake of Fe and Zn in 45‐day‐old bean plants. However, it significantly (p < 0.05) increased bean‐seed Cu content and accumulation. The double inoculation resulted in significantly (p < 0.05) higher micronutrient concentrations than Trichoderma inoculation alone in 45‐day‐old plants. In contrast to beans, the effects of microbial inoculations were less in wheat. However, dual inoculation significantly (p < 0.05) increased Zn content by 45% and Zn accumulation by 40% above the uninoculated control. Inoculation with plant growth–promoting microorganisms appears to be a promising strategy to combat micronutrient deficiencies.     

Effects of Arbuscular Mycorrhizal Inoculation and Phosphorus Application on Yield and Nutrient Uptake of Yam

To be sustainable, production in the traditional yam cropping system, faced with declining soil fertility, could benefit from yam–arbuscular mycorrhizal (AM) symbiosis, which can improve nutrient uptake, disease resistance, and drought tolerance in plants. However, only limited information exists about AM colonization of yam. A pot experiment was conducted to collect information on the response of two genotypes (Dioscorea rotundata accession TDr 97/00903 and D. alata accession TDa 297) to AM inoculation (with and without) and phosphorus (P) (0, 0.05, 0.5, and 5 mg P kg^–1 soil). Factorial combinations of the treatments were arranged in a completely randomized design with four replicates. The percentage of AM colonization was significantly lowered at 5 mg P kg^–1 soil rate in mycorrhizal plants of both genotypes. TDr 97/00903 showed more responsiveness to AM inoculation than TDa 297. The greatest AM responsiveness for tuber yield (52%) was obtained at 0.5 mg P kg^–1 soil rate for TDr 97/00903. Mycorrhizal inoculation significantly increased root dry weight and tuber yield of TDr 97/00903 with the greatest values obtained at the 0.5 mg P kg^–1 soil rate. Arbuscular mycorrhizal inoculation did not lead to significant (P < 0.05) changes in root length and area. Phosphorus application significantly increased the shoot dry weight and root diameter of TDa 297. Uptake of P was greatest at 0.5 mg P kg^–1 soil in both genotypes and was significantly influenced by AM inoculation. Nitrogen (N) and potassium (K) uptake were greatest in mycorrhizal plants at 0.05 mg P kg^–1 soil for TDr 97/00903 but at 0.5 mg P kg^–1 soil of nonmycorrhizal plants of TDa 297. The increased tuber yield and nutrient uptake observed in the mycorrhizal plants indicate the potential for the improvement of nutrient acquisition and tuber yield through AM symbiosis.     

ARBUSCULAR MYCORRHIZAL FUNGI AND PIRIFORMOSPORA INDICA INDIVIDUALLY AND IN COMBINATION WITH RHIZOBIUM ON GREEN GRAM

Three species of AM fungi, Glomus mosseae, Glomus microcarpum, Gigaspora margarita and a fungus that mimics the properties of AM fungi, Piriformospora indica, were tested on green gram [Phaseolus aureus Roxb. (= Vigna radiata var. radiata)] individually and in combination with Rhizobium for their influence on growth and seed yield. The growth parameters analyzed were dry biomass, total leaf area, total chlorophyll,% root colonization, nodulation, and nitrogen, phosphorus, and potassium (NPK) content of leaf tissues using standard methodologies. Glomus microcarpum was found to be more effective in promoting biomass and seed yield when applied alone. But in combination with Rhizobium, G. mosseae enabled highest production of biomass. The tissue nitrogen content was high in G. microcarpum—Rhizobium dual inoculated plants. Many other characteristics were high in dual inoculation, while tissue P was high in individual treatment of G. mosseae. Piriformospora indica was not found to be a good synergist on green gram.     

Uptake and metabolism of nitrate in mycorrhizal plants as affected by water availability and N concentration in soil

We compare the effect of arbuscular mycorrhizal (AM) colonization and PO₄^?3 fertilization on nitrate assimilation, plant growth and proline content in lettuce plants growing under well‐watered (?0.04 MPa) or drought (?0.17 MPa) conditions. We also tested how AM‐colonization and PO₄^?3 fertilization influenced N uptake (¹⁵N) and the percentage of N derived from the fertilizer (% NdfF) by plants under a concentration gradient of N in soil. Growth of mycorrhizal plants was comparable with that of P‐fertilized plants only under well‐watered conditions. Shoot nitrogen content, proline and nitrate reductase activity were greater in AM than in P‐fertilized plants under drought. The addition of 100 μg g^?1 P to the soil did not replace the AM effect under drought. Under well‐watered conditions, AM plants showed similar (at 3 mmol N), greater (at 6 mmol N) or lesser (at 9 mmol N) %NdfF than P‐fertilized plants. Comparing a control (without AM inoculation) to AM plants, differences in % NdfF ranged from 138% (3 mmol N) to 22.6% (6 mmol N) whereas no differences were found at 9 mmol N. In comparison with P fertilization, mycorrhizal effects on %NdfF were only evident at the lowest N levels, which indicated a regulatory mechanism for N uptake in AM plants affected by N availability in the soil. At the highest N level, P‐fertilized plants showed the greatest %NdfF. In conclusion, AM symbiosis is important for N acquisition and N fertilizer utilization but this beneficial mycorrhizal effect on N nutrition is reduced under large quantities of N fertilizer.     

EFFECTS OF SINGLE,DUAL AND TRIPLE INOCULATIONS WITH BACILLUS SUBTILIS,BACILLUS MEGATERIUM AND RHIZOBIUM LEGUMINOSARUM BV. PHASEOLI ON NODULATION,NUTRIENT UPTAKE,YIELD AND YIELD PARAMETERS OF COMMON BEAN (PHASEOLUS VULGARIS L. CV. ‘ELKOCA-05’)

This study was conducted in order to investigate the effects of single, dual, and triple inoculations with Rhizobium, N₂-fixing Bacillus subtilis (OSU-142), and P-solubilizing Bacillus megaterium (M-3) on nodulation, plant growth, nutrient uptake and seed yield of common bean (Phaseolus vulgaris L. cv. ‘Elkoca-05’) in comparison to control and mineral fertilizer application under field conditions in 2006 and 2007 in the cold highland in Erzurum plateau (29° 55′ N and 41° 16′ E with an altitude of 1850 m), Turkey. Bacterial inoculations significantly increased all the parameters investigated compared with the control treatment, equal to or higher than nitrogen (N), phosphorus (P), and NP treatments. The lowest shoot dry weight and chlorophyll content values were recorded in the control treatment and the bacterial inoculations increased shoot dry weight by 19.7–54.3% and chlorophyll content by 34.1–59.3% over control. Nodule dry weight significantly increased in Rhizobium alone treatment. Additionally, nodulation by native soil Rhizobium population was increased in single inoculations of OSU-142 and M-3. Significant increases of the seed yield under different inoculation treatments ranged between by 6.6% (Rhizobium + OSU-142 + M-3) and 12.2% (OSU-142 alone) over the control whereas N, P and NP applications corresponded to increases of 5.6%, 4.0% and 7.4%, respectively. All bacterial inoculations, especially triple inoculation, significantly increased uptake of macronutrients and micronutrients by common bean. In conclusion, seed inoculation with Rhizobium, OSU-142 and M-3, especially OSU-142 alone, may substitute partially costly NP fertilizers in common bean production even in cold highland areas such as in Erzurum.     

Effect of seed phosphorus concentration on nodulation and growth of three common bean cultivars

Abstract

An experiment was conducted in the greenhouse to evaluate the effects of seed phosphorus (P) concentration on growth, nodulation, and nitrogen (N) and P accumulation of three common bean (Phaseolus vulgaris L.) cultivars. Seeds were produced under low or high soil P levels, and soaked, or not, in 200 mM KH₂PO₄ solution. The experiment had a 3×3×2×2 factorial block design: three cultivars (ICA Col 10103, Carioca and Honduras 35), three levels of applied P (15, 30 and 45 mg P kg^?1 soil), two native seed P concentrations, and two seed soaking treatments. Plants were harvested at flowering. Soaked seeds increased the number, dry mass and P content of nodules, but did not affect plant growth. Plants originated from seeds with high native P concentration presented higher shoot dry mass and nodule number and mass at every soil P level, and were less responsive to increased soil P supply, than plants from low seed P. In plants from seeds with high P, soil P levels did not alter significantly root dry mass, while in plants from seeds with low P bean cultivars expressed wider differences in root dry mass. The genotypic variability of nodulation was influenced by soil P levels and seed P concentration. Both higher soil or seed P supply enhanced N and P accumulation in shoots. These results indicate that a high seed P concentration produces plants less dependent on soil P supply, and can enhance nodulation and N₂ fixation of common bean. Seed P supply affected the cultivar performance, and should be considered in evaluation of bean genotypes.     

Influence of arbuscular mycorrhizal fungi and salinity on growth,biomass, and mineral nutrition of<Emphasis Type="Italic"> Acacia auriculiformis</Emphasis>

The effect of salinity on the efficacy of two arbuscular mycorrhizal fungi, Glomus fasciculatum and G. macrocarpum, alone and in combination was investigated on growth, development and nutrition of Acacia auriculiformis. Plants were grown under different salinity levels imposed by 0.3, 0.5 and 1.0 S m^-1 solutions of 1 M NaCl. Both mycorrhizal fungi protected the host plant against the detrimental effect of salinity. The extent of AM response on growth as well as root colonization varied with fungal species, and with the level of salinity. Maximum root colonization and spore production was observed with combined inoculation, which resulted in greater plant growth at all salinity levels. AM fungal inoculated plants showed significantly higher root and shoot weights. Greater nutrient acquisition, changes in root morphology, and electrical conductivity of soil in response to AM colonization was observed, and may be possible mechanisms to protect plants from salt stress.     

ARBUSCULAR MYCORRHIZA,AZOSPIRILLUM AND CHEMICAL FERTILIZERS APPLICATION TO BABY CORN (ZEA MAYS L.): EFFECTS ON PRODUCTIVITY,NUTRIENTS USE EFFICIENCY,ECONOMIC FEASIBILITY AND SOIL FERTILITY

The study was investigated at Agricultural Experimental Farm, Giridih, India during winter seasons of 2007–2008 and 2008–2009. Plants grown with 100% recommended dose of fertilizer (RDF) [nitrogen (N): phosphorus pentoxide (P₂O₅): potassium oxide (K₂O) = 150:60:60 kg ha^?1] + AM + Azospirillum (T₁₅) produced maximum chlorophyll, baby cob, and green fodder yield. Root biomass was highest with application of 150% RDF + arbuscular mycorrhizae (AM) + Azospirillum (T₁₆). Co-inoculated plants produced higher chlorophyll, root biomass resulted higher cob and green fodder yield. Biofertilizers supplied along with chemical fertilizers saved 70, 29, and 33 kg N, P₂O₅ and K₂O per hectare, respectively. Nutrient (NPK) uptake was greatest in T_15. Residual soil fertility in terms of NPK was recorded maximum in T_16. Although, co-inoculated plots built up higher residual soil fertility as compare to sole inoculation. Nutrients use efficiency and benefit cost ratio were higher due to application of 50% RDF with co-inoculants. T₁₆ was most costly whereas T₁₄ (50% RDF + AM + Azospirillum) was most beneficial.     

生物炭和AM真菌配施对连作辣椒生长和土壤养分的影响

研究生物炭和丛枝菌根(arbuscularmycorrhizal,AM)真菌对连作辣椒生长和土壤养分的影响,可为辣椒连作土壤改良和新型肥料的开发提供理论依据。采用温室盆栽试验,设置4个生物炭添加水平(0、1%、2%、3%), 2个接菌水平[接菌(+AM)和不接菌(-AM)]。辣椒生长60 d后收获并测定其生理指标、土壤酶活性及土壤养分含量。结果表明,施加生物炭和接种AM真菌处理促进了连作辣椒的生长,提高了辣椒叶片净光合速率、蒸腾速率、气孔导度和叶绿素含量。接种AM真菌对辣椒的促生效果弱于生物炭,而生物炭和AM真菌配施的促生效果最佳。接种AM真菌促进辣椒对P吸收的效果优于生物炭;但对于K吸收来说,施加生物炭的效果优于接菌。生物炭(3%)和AM真菌配施条件下,辣椒根部N、P、K含量分别较对照(0生物炭和-AM处理)显著提高74.04%、106.42%和78.82%。生物炭(3%)与AM真菌配施处理菌根侵染效果最佳,侵染率高达58.96%,较0生物炭+AM处理提高41.59%。土壤pH随生物炭添加量的增加呈增加趋势,但差异不显著。土壤脲酶、蔗糖酶活性随生物炭添加量的增加呈增加趋势,且差异显著,接种AM真菌处理对其影响不显著。土壤速效钾、有效磷、有机质含量随生物炭添加量的增加而增加,接种AM真菌对土壤有机质含量、阳离子交换量(CEC)无显著影响。土壤速效钾、有效磷、碱解氮含量均在生物炭(3%)和AM真菌配施条件下达最大。与单一处理相比,生物炭和AM真菌配施在促进连作辣椒生长、改善连作土壤养分方面具有显著的协同增效作用,尤其是3%生物炭与AM真菌配施条件下效果最佳。     

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.     

Arbuscular mycorrhizal fungi mitigates heavy metal toxicity adverse effects in sewage water contaminated soil on Tagetes erecta L

The aim of this experiment was to evaluate the impact of colonization with arbuscular mycorrhizal (AM) fungus Glomus constrictum on the biomass production, flower quality, chlorophyll content, macronutrients and heavy metals content of marigold (Tagetes erecta L.) planted under uncontaminated soil and watered with various rates of sewage water. Sewage water utilization significantly decreased biomass production, characters of flower, nutrient concentration and rates of mycorrhizal colonization of mycorrhizal (M) and non-mycorrhizal (NM) marigold as compared to control untreated plants especially at the higher rates, but the reduction rate was proportionally higher in non-AM treatments. Mycorrhizal plants had significantly greater yield, relative chlorophyll content, leaf area, flower quality and element (P, N, K and Mg) content compared to non-inoculated marigold plants irrigated with or without sewage water. Furthermore, AM inoculation had highly decreased heavy metal (Zn, Co, Mn, Cu) content in tissues as compared to equivalent non-inoculated plants grown under sewage water application. Growing marigold with AM inoculum can reduce toxicity of heavy metals and enhance biomass production and P uptake. The results support the view that AM have a protective function for the host plant, hence playing a potential function in soil polluted immobilization processes, and thus are of assessing the potential of phytoremediation of heavy metals in sewage water contaminated soil.