Growth and interactions of arbuscular mycorrhizal fungi in soils from limestone and acid rock habitats

Arbuscular mycorrhizal (AM) development in different soil types, and the influence of AM fungal hyphae on their original soil were investigated. Plantago lanceolata, which can grow in soils of a very wide pH range, was grown in two closely related limestone soils and an acid soil from rock habitats. Plants were colonised by the indigenous AM fungal community. The use of compartmented systems allowed us to compare soil with and without mycorrhizal hyphae. Root colonisation of P. lanceolata was markedly higher in the limestone soils (30-60%) than in the acid soil (5-20%), both in the original habitat and in the experimental study. Growth of extraradical AM fungal hyphae was detected in the limestone soils, but not in the acid soil, using the signature fatty acid 16:1ω5 as biomass indicator. Analysis of signature fatty acids demonstrated an increased microbial biomass in the presence of AM fungal hyphae as judged for example from an increased amount of NLFA 16:0 with 30 nmol g⁻¹ in one of the limestone soils. Bacterial activity, but not soil phosphatase activity, was increased by around 25% in the presence of mycorrhizal hyphae in the first harvest of limestone soils. AM fungal hyphae can thus stimulate microorganisms. However, no effect of AM hyphae was observed on the soil pH or organic matter content in the limestone soils and the available P was not depleted.     

沿海拔梯度分布的柑橘园中土壤肥力因子与丛枝菌根共生体的关系

Arbuscular mycorrhizal(AM) symbionts are able to greatly affect soil fertility. However, the relationships between AM symbiosis development levels and citrus mycorrhizosphere soil fertility remain weakly known in field. In our study, AM colonization, spore density, hyphal length density, and glomalin-related soil protein(GRSP) content in citrus(Robertson naval orange grafted on Citrus reticulata Blanco) orchards along an altitudinal gradient were investigated seasonally in southern China. The results showed that AM colonization and abundances of spore and hyphae fluctuated significantly in different seasons and altitudes. The highest AM colonization(83.03%) was observed in orchards at 200 m above sea level in summer, spore density(16.8 spores g-1soil) in orchards at 400 m in autumn, and hyphal length density(2.36 m g-1soil) in orchards at 600 m orchards in summer; while the lowest values(43.60%, 2.7 spores g-1soil and 0.52 m g-1soil of AM colonization, spore density, and hyphal length density, respectively) were all observed in orchards at 800 m in winter. Correlation analyses demonstrated that the soil properties such as soil organic matter,alkali-hydrolyzable N, available P, and p H were significantly(P < 0.05) positively correlated with either citrus total AM colonization or the abundances of spore and hyphae. GRSP was significantly(P < 0.05) positively correlated with soil organic matter and p H.Redundancy analysis supported that soil environmental factors such as altitude, GRSP, soil organic matter, and alkali-hydrolyzable N severely(Monte Carlo permutation tests, P = 0.002) influenced AM colonization and abundances of spore and hyphae in citrus orchards. Our data demonstrated that soil environmental factors are vital in determining AM symbiosis development in citrus orchards.     

肝片形吸虫雷蚴与尾蚴的扫描电镜观察

肝片形吸虫的母雷蚴、早期子雷蚴、成熟子雷蚴及尾蚴表被结构经扫描电镜观察：在母雷蚴及早期子雷蚴的口孔周围有乳突分布；雷蚴的围领呈领圈样环绕，围领基部的一侧有一个产孔，产孔的开口处呈唇样的构造，从母雷蚴、早期子雷蚴至成熟子雷蚴的发育，其体表绒毛样构造日趋发达。尾蚴背部密布尖刀形棘，腹部具有许多不规则的突起，其间分布有许多微孔；口吸盘及周围无乳突分布，但在腹吸盘周围分布有排列整齐的指状突起。尾蚴体部与尾部相连处有一环形颈状结构，尾蚴尾干背面为一槽状的皱襞。     

Antagonistic rhizoplane bacteria induce diverse morphological alterations in Peronosporomycete hyphae during <Emphasis Type="Italic">in vitro</Emphasis> interaction

A total of 150 bacteria were isolated from rhizoplanes of the host and non-host plants of a phytopathogenic Peronosporomycete Aphanomyces cochlioides. Upon screening, 5% of the isolates were evaluated as antagonists as they inhibited radial growth of A. cochlioides AC-5 hyphae in a dual culture assay. In addition, those antagonistic bacteria also induced characteristic morphological alterations in the A. cochlioides AC-5 hyphae that grew towards bacterial colonies. Hyphal morphological alterations observed in AC-5 and other tested strains of Peronosporomycetes included excessive branching, curly growth, unusually longer and pointed tip formation and swelling; all of these were comparable to the alterations induced by known antimicrobial compounds. Among the antagonistic bacteria, Pseudomonas sp. strain EC-S101 induced a unique branching pattern (tree-like) in AC-5 hyphae by continuous apical bifurcation of successive hyphae, where increases in number of branches and hyphal area were linearly correlated with time up to 10 h. Our observations suggested that the pathogen might have lost its ability of normal branch production; however maintained the capability of self-branching. Soluble extracts from the culture fluids of Pseudomonas sp. strain EC-S101 and Stenotrophomonas maltophilia EC-S105 induced similar excessive branching and curly growth in A. cochlioides hyphae as the respective bacterium. These results revealed that bacterial metabolites appeared to be responsible for induction of morphological alterations. Interestingly, the antagonistic bacteria that induced hyphal morphological alterations, also efficiently suppressed in vivo damping-off disease caused by AC-5. We suggest that antagonistic rhizoplane bacteria have the capability to induce diverse morphological alterations in Peronosporomycetes hyphae during in vitro interactions. Hyphal morphological alterations associated with growth inhibition and the induction of characteristic morphological changes indicate antagonistic activity against the Peronosporomycete.     

Intraradical hyphae phosphatase of the arbuscular mycorrhizal fungus, Gigaspora margarita

An alkaline phosphatase in the intraradical hyphae of arbuscular mycorrhizal fungi was found to be closely related to an improvement of plant growth. To detect the phosphatase activity in a crude extract of mycorrhizal roots, phosphatase isozymes in mycorrhizal and non-mycorrhizal onion roots were compared with those in Gigaspora margarita by electrophoresis. A mycorrhiza-specific band was found when the phosphatase was stained under alkaline conditions. To clarify the origin of this phosphatase, the phosphatase extracted from intraradical hyphae was also compared with the phosphatase from mycorrhizal roots by electrophoresis. The intraradical hyphae was isolated from mycorrhizal roots by enzyme digestion followed by Percoll gradient centrifugation. The soluble protein was extracted from the hyphae by ultra-sonication after treatment with chitinase. A phosphatase in the hyphal soluble protein showed a similar, but slightly higher, relative mobility on the gel, compared with the mycorrhiza-specific phosphatase from roots. By adding the hyphal extract to the root extract, the relative mobility of the mycorrhiza-specific phosphatase was slightly changed and became identical to that of the phosphatase in the hyphae. This indicated that the specific band of phosphatase found in the crude extract from mycorrhizal roots was of intraradical hyphal origin. Received: 16 April 1997     

蛹虫草人工栽培技术的改进

以人工栽培的蛹虫草鲜品为材料,通过组织分离和培养手段获得的虫草种源同野生虫草组分种源Ｆｏｍ１相比产量性状没有明显差异;在栽培方法上采用搔菌和喷施５％生石灰水溶液,较好地解决了蛹虫草栽培中菌丝徒长、不转色、不现草的技术难题。     

First report of Fusarium oxysporum species complex infection in zebrafish culturing system

Fusarium oxysporum species complex (FOSC) is a highly diverse fungus. Recently, F. oxysporum infection was identified from zebrafish (Danio rerio) culturing system in Korea. Initially, a rapid whitish smudge was appeared in the water with the fungal blooming on walls of fish tanks. Microscopic studies were conducted on fungal hyphae, colony pigmentation and chlamydospore formation and the presence of macro‐ and microspores confirmed that the isolated fungus as F. oxysporum. Furthermore, isolated F. oxysporum was confirmed by internal transcribed spacer sequencing which matched (100%) to nine F. oxysporum sequences available in GenBank. Experimental hypodermic injection of F. oxysporum into adult zebrafish showed the development of fungal mycelium and pathogenicity similar to signs observed. Histopathologic results revealed a presence of F. oxysporum hyphae in zebrafish muscle. Fusarium oxysporum growth was increased with sea salt in a concentration‐dependent manner. Antifungal susceptibility results revealed that F. oxysporum is resistant to copper sulphate (up to 200 μg mL^?1) and sensitive to nystatin (up to 40 μg mL^?1). This is the first report of FOSC from zebrafish culture system, suggesting it appears as an emerging pathogen, thus posing a significant risk on zebrafish facilities in the world.     

海南东寨港红树林植物根系丛枝菌根真菌的初步调查

对海南东寨港国家级自然保护区3个地点(三江、塔市、保护站)的红树林植物丛枝菌根真菌(AMF)侵染状况进行了调查研究。结果表明,海南东寨港红树林生长区中14种红树植物的根内均发现菌丝、泡囊等AMF侵染结构,且都有较高的感染率,其中海桑、无瓣海桑、秋茄的总感染率均达到100%。     

Contribution of Roots and Mycorrhizal Hyphae on Phosphorus Efficiency of Maize (Zea mays,L.) Genotypes Grown on Calcareous Soil—A Mechanistic Modeling Approach

ABSTRACT

This work was conducted to study phosphorus (P) efficiency of two maize genotypes (Zea mays, L.) in calcareous soil grown in potted soil with two levels of P in soil by adding 40 and 270 mg P/kg soil. Half of the pots were inoculated with arbuscular mycorrhizal fungi (AMF) (Rhizoglomus irregulare). The maize genotypes were harvested two times at 35 and 50 days after transplanting. The plant dry matter, root length and Plant P uptake of maize genotype Hagen 1 without mycorrhizal fungi (AMF) increased significantly compared with Hagen 9 at a low P level. In contrast, there was no significant difference between two maize genotypes inoculated with AMF under the same P level. The predicted value increased rapidly with increasing P levels from about 70% up to 97% in both maize genotypes with and without mycorrhizal fungi. At a low P level, the mycorrhizae hyphae contributed by about 31.6% and 30.2% of the predicted total P uptake in maize genotype Hagen 1 and Hagen 9, respectively. The results of this study suggested that the P-inefficient genotype Hagen 9 improved with inoculation with mycorrhizal fungi under a low P level at the same conditions of this experiment. Also, root growth system and mycorrhizal hyphae length would be a suitable plant parameter for studying P efficient maize genotypes, especially under limited P supply. The current study clearly pointed out that the mechanistic simulation model (NST 3.0) provides useful tools for studying the role of AMF in P uptake of plant.     

Nutrient availability and saffron corms growth affected by composted pistachio residues and commercial poultry manure in a calcareous soil

ABSTRACT

Utilizing the proper techniques of plant residue composting can play a significant role in reducing the adverse environmental impacts of chemical fertilizers. Herein the effects of commercial poultry manure (CPM) and composted pistachio residues (CPR) on nutrient availability and saffron daughter corms behavior in a calcareous soil were evaluated as a greenhouse experiment based on completely randomized design arranged in factorial with three replicates. In this study, CPM rates (0, 3, 6, and 9 t ha^?1) and CPR levels (0, 20, 40, and 60 t ha^?1) were assigned as the first and the second experimental factors, respectively. From the results, CPM or CPR application caused a significant increase in small (≤5 g), mid (5.1–10 g) and large-sized (10.1–15 g) daughter corms number. The highest N (P) concentration in small, mid and large-sized daughter corms was recorded when 9 t ha^?1 CPM was applied along with 60 t ha^?1 CPR. Soil organic carbon content increased with increasing CPM or CPR levels. The same trend was also observed for soil available N, P, K, and electrical conductivity. By contrast, CPM or CPR levels caused a significant reduction in soil pH. According to the results, pistachio compost can be considered as an eco-friendly alternative to chemical fertilizers to improve soil fertility in saffron farms.