Growth Response and Nutrient Uptake of Eriobotrya japonica Plants Inoculated with Three Isolates of Arbuscular Mycorrhizal Fungi Under Water Stress Condition

Mycorrhizal technique is a promising biotechnology in horticultural industry, benefiting plants exposed to diverse abiotic stresses. In this study, the effects of three arbuscular mycorrhizal fungi (AMF), Acaulospora laevis, Glomus mosseae, and Glomus caledonium on plant growth and nutrient uptake of loquat (Eriobotrya japonica Lindl.) seedlings under three water regimes (well watered, water stressed-slight, water stressed-heavy) were investigated. Results showed that inoculated seedlings had higher dry biomass, plant height, and total leaf areas than those un-inoculated ones. AMF effect was the greatest for water stressed-heavy seedlings, followed by water stressed-slight seedlings and well watered seedlings. All AMF species increased the uptake of nitrogen (N) potassium (K), phosphorus (P), calcium (Ca), magnesium (Mg), zinc (Zn), copper (Cu), and the mycorrhizal contributions to the nutrient uptake were positively related to that to the biomass. Data suggest that AMF inoculation increases the tolerance of loquat seedlings to drought stress, and the improved nutrient uptake by AMF contributes greatly to the tolerance.     

丛枝菌根真菌的外生菌丝对土壤水稳性团聚体形成的影响

应用三室根箱装置 ,研究了接种丛枝菌根真菌 Glomus mosseae和 Glomus versiform对玉米根分泌物以及菌根真菌外生菌丝对沙土的水稳性大团聚体形成的作用。结果表明 :接种 Glom us mosseae和 Glomus versiform提高了玉米根系分泌物的总量 ,进而增加了根系粘结的土壤重量。菌根菌丝对土壤中 5～ 2 mm水稳性大团聚体形成的贡献为 10 0 % ;在土壤中菌根菌丝的密度分布与 2～ 1mm水稳性团聚体的含量分布是一致的 ,都表现出随着距离根系表面距离的增加而增加的趋势。这些结果说明菌根菌丝直接促进了土壤团聚体的形成 ,对 5～ 2 m m水稳性大团聚体而言 ,没有菌根菌丝的作用就不能形成 ;菌根菌丝对 5～ 2 mm和 2～ 1m m水稳性团聚体的形成主要是通过其分泌物粘结和菌丝网络对土壤的缠绕作用所致 ,菌根菌丝对这两种水稳性团聚体形成的贡献甚至超过了根系的作用。     

Growth and Nutrient Content of Trifoliate Orange Seedlings Influenced by Arbuscular Mycorrhizal Fungi Inoculation in Low Magnesium Soil

A pot experiment was conducted to examine the effects of arbuscular mycorrhizal fungi, Glomus versiforme, G. mosseae, and G. intraradices on growth and nutrition of trifoliate orange (Poncirus trifoliata) seedlings under magnesium (Mg)-nontreated and Mg-treated conditions. Whether treated with Mg or not, G. versiforme inoculation significantly enhanced the growth and concentrations of Mg, phosphorus, calcium, potassium, zinc, and copper in shoots or roots, and activities of acid phosphatase, catalase, invertase, and urease in rhizosphere soils. Additionally, there were higher levels of chlorophyll, proline, soluble sugar and protein in leaves, root viability, superoxide dismutase, peroxidase and catalase in leaves and roots, but lower malondialdehyde content in leaves and roots of mycorrhizal seedlings than non-mycorrhizal ones. Data demonstrated that G. versiforme-inoculated citrus seedlings exhibited higher levels of soil enzymes, osmoregulation, and antioxidant matters, leading to improvement of growth and nutrition of seedlings in low Mg soil.     

Influence of Vesicular Arbuscular Mycorrhizal Fungi and Applied Phosphorus on Root Colonization in Wheat and Plant Nutrient Dynamics in a Phosphorus-Deficient Acid Alfisol of Western Himalayas

Vesicular arbuscular mycorrhizal (VAM) fungi symbiosis confers benefits directly to the host plant's growth and yield through acquisition of phosphorus and other macro- and micronutrients, especially from phosphorus (P)–deficient acidic soils. The inoculation of three VAM cultures [viz., local culture (Glomus mosseae), VAM culture from Indian Agricultural Research Institute (IARI), New Delhi (Glomus mosseae), and a culture from the Centre for Mycorrhizal Research, Energy Research Institute (TERI), New Delhi (Glomus intraradices)] along with P fertilization in wheat in a P-deficient acidic alfisol improved the root colonization by 16–24% while grain and straw yields increased by 12.6–15.7% and 13.4–15.4%, respectively, over the control. Uptake of nitrogen (N), P, potassium (K), iron (Fe), manganese (Mn), zinc (Zn), and copper (Cu) was also improved with VAM inoculation over control, but the magnitude of uptake was significantly greater only in the cases of P, Fe, Zn, and Cu. Inoculation of wheat with three VAM cultures in combination with increasing inorganic P application from 50% to 75% of the recommended P₂O₅ dose to wheat through the targeted yield concept following the soil-test crop response (STCR) precision model resulted in consistent and significant improvement in grain and straw yield, macronutrient (NPK) uptake, and micronutrient (Fe, Mn, Zn, Cu) uptake in wheat though root colonization did not improve at P₂O₅ doses beyond 50% of the recommended dose. The VAM cultures alone or in combination with increasing P levels from 50% to 75% P₂O₅ dose resulted in reduction of diethylenetriaminepentaacetic acid (DTPA)–extractable micronutrient (Fe, Mn, Zn, Cu) contents in P-deficient acidic soil over the control and initial fertility status, although micronutrient contents were relatively greater in VAM-supplied plots alone or in combination with 50% to 75% P₂O₅ dose over sole application of 100% P₂O₅ dose, thereby indicating the positive role of VAM in nutrient mobilization and nutrient dynamics in the soil–plant system. There was significant improvement in available N and P status in soil with VAM inoculation coupled with increasing P levels upto 75% P₂O₅ dose, although the greatest P buildup was obtained with sole application of 100% P₂O₅ dose. The TERI VAM culture (Glomus intraradices) showed its superiority over the other two cultures (Glomus mosseae) in terms of crop yield and nutrient uptake in wheat though the differences were nonsignificant among the VAM cultures alone or at each P level. Overall, it was inferred that use of VA-mycorrhizal fungi is beneficial under low soil P or in low input (nutrient)–intensive agroecosystems.     

Improving Phosphorus Use through Co-inoculation of Vesicular Arbuscular Mycorrhizal Fungi and Phosphate-Solubilizing Bacteria in Maize in an Acidic Alfisol

Performance of three vesicular arbuscular mycorrhizal (VAM) fungi cultures and a phosphate-solubilizing bacteria (PSB) culture alone or in combination with or without 75% of the recommended P₂O₅ dose based on soil-test crop response model was examined in maize in a phosphorus (P)-deficient acidic Alfisol in a glasshouse pot experiment. Sole application of VAM besides co-inoculation with PSB (Pseudomonas striata) and inorganic P stimulated mycorrhizal root colonization. Sole application of PSB, VAM_T (Glomus intraradices), and VAM_I (Glomus mosseae) as well as co-inoculation of VAM with PSB significantly improved crop productivity besides grain protein content, thus indicating a synergistic interaction between VAM and PSB. Application of VAM_T or VAM_I + PSB + 75% P₂O₅ remained at par with sole application of 100% P₂O₅ dose with regard to productivity, nutrient uptake, and soil fertility status (particularly P), thus indicating economization of fertilizer P to the tune of about 25% without compromising crop productivity and soil fertility in an acidic Alfisol.     

Effects of Molybdenum,Nickel, and Nitrogen Sources on the Mineral Nutrition and Growth of Rice Plants

Upland rice plants, cultivar ‘IAC 202,’ were grown in nutrient solution until full tillering. Treatments consisted of ammonium nitrate (AN) or urea (UR) as nitrogen (N) source plus molybdenum (Mo) and/or nickel (Ni): AN + Mo + Ni, AN + Mo ? Ni, AN ? Mo + Ni, UR + Mo + Ni, UR + Mo ? Ni, and UR ? Mo + Ni. The experiment was carried out to better understand the effect of these treatments on dry‐matter yield, chlorophyll, net photosynthesis rate, nitrate (NO₃ ^?‐N), total N, in vitro activities of urease and nitrate reductase (NR), and Mo and Ni concentrations. In UR‐grown plants, Mo and Ni addition increased yield of dry matter. Regardless of the N source, chlorophyll concentration and net photosynthesis rate were reduced when Mo or Ni were omitted, although not always significantly. The omission of either Mo or Ni led to a decrease in urease activity, independent of N source. Nitrate reductase activity increased in nutrient solutions without Mo, although NO₃ ^?‐N increased. There was not a consistent variation in total N concentration. Molybdenum and Ni concentration in roots and shoots were influenced by their supply in the nutrient solution. Molybdenum concentration was not influenced by N sources, whereas Ni content in both root and shoots was greater in ammonium nitrate–grown plants. In conclusion, it can be hypothesized that there is a relationship between Mo and Ni acting on photosynthesis, although is an indirect one. This is the first evidence for a beneficial effect of Mo and Ni interaction on plant growth.     

Arbuscular Mycorrhizal Association for Growth and Nutrients Assimilation of Pharagmites japonica and Polygonum cuspidatum Plants Growing on River Bank Soil

Effects of arbuscular mycorrhizal fungi (AMF) on the growth, nutrient absorption, and inoculation effectiveness of AMF on pioneer plants Pharagmites japonica (C4) and Polygonum cuspidatum (C3) were evaluated by performing a pot experiment in a greenhouse at Saitama University, Japan. AMF spores were collected from the commercial product, Serakinkon. The average colonization levels of P. japonica and P. cuspidatum were 24–33% and 0.2–0.5% respectively and no colonization was found in sterilized soil treatment. AMF colonization increased the plant dry mass, phosphorus (P), and nitrogen (N) concentrations of P. japonica’s roots, stems, and leaves when AMF applied with natural and sterilized soil compared with only sterilized and natural soil. This was a significant effect for N-loss minimization from soil. Maximum value showed when P. japonica was grown with natural soil in combination with AMF whereas P. cuspidatum showed very less or a negative response to AMF colonization in all cases.     

Nutrition and Production of Phaseolus vulgaris (BRS estilo) Following Boron Application on Soil

Boron (B) application is an important strategy in highly productive systems, since this micronutrient is involved in amide syntheses, which is related to the grain yield. In this way, the aim of this work was to evaluate the B fertilization effect in nutrition and production of common beans. The experiment was carried out under greenhouse condition, in an entirely randomized design, with five B doses (0, 1, 2, 4, and 6 kg ha^?1) and four repetitions. The relative chlorophyll index, dry mass production, level and accumulation of B were measured. Boron levels in leaves of common beans are linearly enhanced after application of increasing B doses. When B level in soil is low (<0.5 mg kg^?1), boron doses lower than 4.9 kg ha^?1 increase dry mass production, with the highest production observed at a dose of 4.8 kg ha^?1, promoting a 56% in dry mass production compared with control.     

土壤因子对西藏高原草地植物AM真菌的影响

于西藏高原中部地区就土壤因子对草地植物AM真菌的影响进行的研究表明：AM真菌孢子密度与菌根侵染率、菌根侵染强度无相关性；土壤质地对AM真菌孢子密度的影响明显大于土壤类型，壤土、粉砂土中AM真菌对植物根系的侵染率高于砂壤土；土壤pH与植物根围土壤孢子密度、菌根侵染率分别呈显著正相关和正相关，与菌根侵染强度则呈负相关；土壤有机质与AM真菌孢子密度呈负相关，菌根侵染效果则随土壤有机质含量的增加而提高；高磷土壤环境对AM真菌产孢和侵染均具不同程度的抑制作用，其中植物菌根侵染率随土壤有效磷含量的提高而呈显著下降；AM真菌对莎草科植物矮生嵩草、扁穗莎草根系具有良好的侵染效应。     

Boron Nutrition,Intracellular Transport,and Knife-Cut Disease in Sunflower

The present study was conducted to investigate in sunflower the processes of boron (B) uptake, intracellular compartmentation, and xylem translocation in response to B supply, ranging from deficiency to incipient toxicity, and to short-term changes in B supply. The experiments were conducted with two sunflower genotypes, selected on the basis of their susceptibility to knife-cut disease. It appears that the roots of the susceptible genotype of sunflower were more sensitive to low B contents in the solution media than the shoots. The decrease in root dry weight in high-B treatments could also indicate it was more sensitive to B toxicity. Though root dry weight decreased, the shoot/root dry-weight ratio was smaller in the resistant genotype, suggesting that this genotype would have a substantially larger root volume, capable of supporting the B demand of its shoots. The B contents in the water-insoluble residue (WIR) of roots were similar for all genotypes and treatments. In contrast, the B concentration in WIR of leaves reached values near saturation only when B started to accumulate in the cell sap (CS) of roots to the level as detected in CS of leaves. The critical values of B concentrations in shoot tissues would then be established after the B requirement for cell walls was satisfied and a proper metabolic B content in CS of roots was reached. Uptake efficiency (UE) values less than 1.00, detected as a result of treatments with high concentrations of B in the nutrient solution, suggested the presence of an exclusion mechanism that restricted B accumulation. The high UE value obtained with low-B treatments indicated that mechanisms other than mass flow had played a role in providing the acquired B.     

Arbuscular Mycorrhizal Fungi and Acclimatization of Micropropagated Citrus

Micropropagated plantlets lack mycorrhizal symbionts and therefore present some physiological hindrances when transferred from axenic to ex vitro conditions. The purpose of the present study was to research the effects of Glomus mosseae and G. versiforme on growth, photosynthesis, and nutrient uptake of micropropagated citrus plantlets at the acclimatization stage. The two mycorrhizal fungi successfully colonized the roots of citrus plantlets after an acclimatization period of 170 days, and the mycorrhizal developments were apt to low levels. Inoculation with G. mosseae improved acclimatized growth performance; increased photosynthetic rates, transpiration rates, and stomatal conductance; and stimulated the accumulations of nitrogen (N), phosphorus (P), calcium (Ca), copper (Cu), zinc (Zn), and manganese (Mn) in leaves and roots compared to the noninoculated treatment. These observations suggested that only G. mosseae was the more efficient fungus, exhibited better adaptation to transplanted conditions, and therefore is appropriate to introduce into the micropropagation protocol of citrus.     

AM真菌和水分条件对稀土尾矿堆中植物生长的影响

通过温室盆栽试验研究了不同水分处理下接种3种丛枝菌根（AM）真菌（Diversispora spurcum、Glomus aggre gatum和Glomus constrictum）后对稀土矿砂中黑麦草（Lolium perenneL.）和狗牙根（Cynodon dactylon（L.）Pers.）植物株高、地上和地下部分干重及植株内Pb和Zn含量的影响。结果表明：不同水分处理下黑麦草和狗牙根与AM真菌均有一定的结合。在干旱胁迫（W1和W2）下,接种3种AM真菌均提高了黑麦草的株高、地上和地下部分干重,其中,接种Glomus aggregatum促进作用最为显著,重度干旱胁迫（W1）处理下接种后黑麦草株高、地上和地下部分干重比对照分别提高了76.16%、202.86%和481.82%;接种Glomus constrictum显著提高了狗牙根的株高、地上和地下部分干重,W1处理下狗牙根接种后的株高、地上和地下部分干重比对照分别提高了119.17%、290.63%和247.37%。接种AM真菌的植株内Pb和Zn含量与AM真菌种类、植物品种、水分处理及重金属性质等相关,在W1处理下接种Glomus constrictum显著降低了黑麦草植株内Pb的含量,而对Zn的含量影响不大;而对于狗牙根,在W1处理下接种Glomus constrictum显著增加了其Pb和Zn的含量。此外,还测定了植物叶片丙二醛和脯氨酸含量,结果显示接种AM真菌明显降低了干旱处理下黑麦草和狗牙根叶片丙二醛和脯氨酸含量,表明接种AM真菌能有效提高植物的抗逆性。     

Effect of Phosphorus Additions and Arbuscular Mycorrhizal Fungal Inoculation on the Growth,Physiology, and Phosphorus Uptake of Wheat Under Two Water Regimes

Drought stress greatly affected the growth and development of wheat in the world, while wheat growth could benefit through improvement of water status and nutrient uptake by mycorrhizal symbiosis or addition of phosphorus (P). Experimental treatments were (a) phosphorus addition (0 and 90 kg/ha), (b) soil water condition (40% field capacity and 95% field capacity), and (c) arbuscular mycorrhizal fungi (AMF, Glomus intraradices) (noninoculation and inoculation) which were conducted in a growth chamber. The results showed that addition of phosphorus and AMF inoculation significantly increased the relative water content and specific leaf area of flag leaves especially under 40% field capacity (water deficit (WD)). The leaf gas exchange parameters were all decreased under WD. The water use efficiency (WUE) and instantaneous WUE (WUEi) was enhanced by WD, AMF inoculation, and phosphorus addition. AMF inoculation and WD significantly decreased the carbon isotope discrimination (CID) of leaf. The P concentrations in stem, grain, and leaf were significantly increased by phosphorus addition, WD, and AMF inoculation. Significant correlations were found between WUE and grain P, stem P, and leaf P concentrations. Leaf CID was significantly negatively correlated with WUE and stem P concentrations. Inoculation of AMF or phosphorus addition could improve the growth, physiology, and phosphorus uptake in spring wheat under drought conditions.     

丛枝菌根真菌对紫花苜蓿吸收土壤中镉和锌的影响

采用温室盆栽试验方法,研究了镉（Cd）、锌（Zn）污染土壤中,8种不同丛枝菌根真菌（AMF）Glomus lamellosum（G.la）、Acaulospora mellea（A.m）、Glomus mosseae（G.m）、Glomus intraradices（G.i）、Glomus etunicatum（G.e）、Glomus constrictum（G.c）、Diversispora spurcum（D.s）、Glomus aggregatum（G.a）对紫花苜蓿（Medicagosativa L.）吸收Cd、Zn的影响。结果表明,Cd、Zn污染下AMF仍然明显侵染紫花苜蓿,并促进紫花苜蓿对Cd、Zn的吸收积累,但不同AMF影响的效应和植株不同部位对重金属的吸收积累规律存在差异。AMF处理下紫花苜蓿根部Cd、Zn含量和积累量明显增加,但地上部Cd、Zn的含量则降低,地上部Zn的积累量也减小,这表明AMF处理减弱了Cd、Zn由根部向地上部的运移,减轻了植物地上部毒害。接种AMF条件下,植株尤其是根部生物量增加是Cd、Zn在其体内含量和积累量增加的重要因素,不同种类AMF促进植株生物量增加的幅度不同,导致植株对Cd、Zn的积累和抗性存在差异。     

Arbuscular Mycorrhizal Fungi Enhance Tolerance of Rosa multiflora cv. Burr to Bicarbonate in Irrigation Water

ABSTRACT

High bicarbonate (HCO₃ ^?) of irrigation water can be detrimental to plant growth in sustainable horticultural production systems. The ability of arbuscular mycorrhizal fungi (AMF), ZAC-19, (composed of Glomus albidum, Glomus claroideum, and Glomus diaphanum) to enhance tolerance to HCO₃ ^? was tested on Rosa multiflora cv. Burr. Arbuscular mycorrhizal colonized and non-inoculated (non-AMF) plants were treated with 0, 2.5, 5, and 10 mM HCO₃ ^?. Increasing HCO₃ ^? concentration and associated high pH and electrical conductivity (EC)—reduced plant growth, nutrient uptake, and acid phosphatase activity, while increasing alkaline phosphatase activity (ALP). Inoculation with AMF enhanced plant tolerance to HCO₃ ^?, as indicated by greater growth (leaf, stem, and total plant dry weight, leaf area and leaf area ratio), leaf elemental concentration [nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), iron (Fe), zinc (Zn), aluminum (Al), boron (B)], leaf chlorophyll concentration, higher mycorrhizal inoculation effect, lower root Fe reductase activity, and generally lower soluble ALP activity. While AMF colonization was reduced by increasing HCO₃ ^? concentration, colonization still occurred at high HCO₃ ^? concentration. At 2.5 mM HCO₃ ^?, AMF plant growth was comparable to plants at 0 mM HCO₃ ^?, further indicating the beneficial effect of AMF for alleviation of HCO₃ ^? plant stress.     

丛枝菌根真菌对鸢尾的促进作用研究

为高效利用水陆两栖植物鸢尾修复污染水体,本研究通过测定不同的丛枝菌根真菌(AMF)与鸢尾构建共生体系的生长指标、土壤理化性质及植物光合作用指标,探讨不同AMF对水生植物鸢尾的促进作用。结果表明:AMF对鸢尾的促进作用主要体现在地上及地下两部分,其中地下部分通过利用其庞大的菌丝网络吸收土壤中的营养物质,进而促进了鸢尾的生长,其中对比无菌剂侵染的空白植物,摩西球囊霉作用的鸢尾对氮元素的吸收率提高71.75%,磷元素的吸收率提高8.36%,而根内球囊霉作用的鸢尾对氮元素的吸收率提高42.55%,磷元素的吸收率提高9.5%;而地上部分则是通过加强叶片气孔导度的开启来调控植物净光合速率与蒸腾速率之间的平衡,进而提高了鸢尾的最优水资源利用率,加快植物的新陈代谢,最终促进植物的生长发育。其中对于鸢尾光合作用的调节摩西球囊霉的促进效果显著好于(P0.05)根内球囊霉。     

丛枝菌根真菌对紫花苜蓿吸收菲和芘的影响

采用横式三隔室盆栽试验方法,研究了丛枝菌根真菌（AMF）根内球囊霉（Glomus intraradices,G.i）对紫花苜蓿（Medicago sativaL.）吸收土壤中菲和芘的影响。结果表明：G.i可与紫花苜蓿形成良好的共生体,侵染率平均达61.20%,不同强度菲和芘污染对G.i菌根侵染率的影响差异不显著;接种G.i的植株根系干重增加59.08%。接种G.i增加了根系和茎叶中菲和芘的含量及积累量,根系和茎叶中菲积累量与其生物量（干重计）间呈显著正相关;与菲相比,接种G.i处理后植株芘含量和积累量的增幅更大。G.i限制了菲和芘从植株根系向茎叶的传输,对芘尤为明显,接种G.i植株根系向茎叶转运芘的比例比不接种对照降低了13.85%～37.47%。     

接种AM真菌对甘薯光合作用及碳磷代谢酶活性的影响

为探讨丛枝菌根真菌和磷水平对甘薯生长特性的影响,采用盆栽试验方法,设置3个P水平(P_0,P_(50),P_(150)mg/kg),研究了接种AM真菌对甘薯生长、光合特性和叶片酶活性的影响。结果表明:接种AM真菌显著增加了甘薯根系侵染率、丛枝丰度、根内菌丝丰度和泡囊丰度。不同磷水平间甘薯的侵染率、丛枝丰度均差异显著,中磷的总体侵染情况显著高于低磷和高磷水平(P0.05)。低磷和中磷条件下,接种处理显著提高了甘薯的生物量和氮磷吸收量(P0.05),其中在磷50mg/kg水平下,接种菌根真菌后甘薯氮磷养分吸收量显著高于未接种处理,地上地下部生物量分别提高了28.6%和73.3%,而高磷条件下接种处理甘薯地上和地下部的生长显著降低。在低磷和中磷水平下,接种AM真菌显著提高了甘薯的净光合速率、气孔导度和蒸腾速率;在中磷水平下接种AM真菌甘薯叶片的蒸腾速率和气孔导度达到最大值,之后随着磷水平的升高而降低;当土壤磷素供应过高时,接种AM真菌属非气孔限制因素导致的光合速率降低(P0.05)。在低磷和中磷水平下,接种菌根真菌显著提高了甘薯叶片中蔗糖合成酶、6-磷酸葡萄糖酸脱氢酶、蔗糖磷酸合成酶和磷酸酶的活性;在高磷水平下,接种后甘薯叶片代谢酶活性明显降低。不同磷水平下的菌根效应表现为P_(50)P_0P_(150),说明接种菌根的效果受土壤磷水平的影响。     

Humus-Rich Compost Increases Lettuce Growth, Nutrient Uptake, Mycorrhizal Colonisation, and Soil Fertility

Sandy soils, typical of Australia's west, either have little or no habitat protection for microbes including arbuscular mycorrhizal (AM) fungi, which are essential for nutrient cycling. To minimize this problem, the application of organic matter, such as humus-rich composts, is necessary during vegetable crop production. This study aimed at determining the effects of humus-rich composts on either indigenous or inoculated AM fungal colonisation in roots, lettuce (Lactuca sativa L. var. Quechua) growth, and soil fertility improvement. Four different humus-rich composts with varying humus contents were applied at the same standard rate to lettuce grown under glasshouse conditions for 10 weeks after sowing and compared with two low-humus composts and non-amended soil (control). Humus-rich composts significantly increased lettuce shoot growth, root growth, and AM fungal colonisation in roots. Humus contents in the composts were also correlated with lettuce shoot and root growth. Soil dissolved organic carbon, microbial biomass carbon, and fertility were increased with the application of humus-rich composts. These humus-rich composts, especially the compost of higher humic acid with and without AM inoculation, might have a significant role in sustainable vegetable production, for example lettuce growth. Overall, the results indicate that supplementation with humus-rich compost is highly beneficial to enhance soil fertility and potentially maintain the sustainability of vegetable production.     

Screening of Arbuscular Mycorrhizal Fungi for Symbiotic Efficiency with Sweet Potato

A greenhouse study was conducted to study the efficiency of 14 isolates of arbuscular mycorrhizal (AM) fungi isolated from a local agricultural soil on the productivity of sweet potato (Ipomoea batatas). The different AM fungi enhanced the biomass and nutritional status of sweet potato seedlings to different extents. The genus Glomus was more effective than Acaulospora or Scutellospora. Efficiency also varied among isolates of Glomus irrespective of individual host plant or location of origin. Intraspecific differences were sometimes greater than interspecific differences. Benefits deriving from fungal isolates were positively correlated with the root-colonization rate and the abundance of extraradical propagules of the AM fungi. Taking plant yield parameters, nutritional status of the plants, and fungal attributes into consideration, GEGM (Glomus etunicatum together with Glomus mosseae) and GE6 (Glomus etunicatum) were the most effective AM symbionts for sweet potato under the experimental conditions.