Arbuscular Mycorrhizal Fungal Density Research Articles

桉树种植对林地土壤丛枝菌根真菌群落结构及多样性的影响

PDF HTML阅读 XML下载 导出引用 引用提醒 桉树种植对林地土壤丛枝菌根真菌群落结构及多样性的影响 DOI: 10.5846/stxb201804140855 作者: 作者单位: 华南农业大学,华南农业大学,华南农业大学,华南农业大学,华南农业大学,华南农业大学 作者简介: 通讯作者: 中图分类号: 基金项目: 国家林业局科技项目（AS-2017-01）；广东省林业厅项目（粤财农[2017]83号） Diversity and structure of the soil arbuscular mycorrhizal fungal community are altered by Eucalyptus plantations Author: Affiliation: South China agricultural University,South China agricultural University,South China agricultural University,South China agricultural University,South China agricultural University,South China Agruiculture University Fund Project: the Project of the Department of Forest of Guangdong Province（YUE CAI NONG [2017] No.83) 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:桉树（Eucalyptus spp.）种植所产生的生态争议已受到广泛关注。丛枝菌根真菌（Arbuscular Mycorrhizal Fungi，AM真菌）是土壤微生物的重要组成部分，与根系共生后可促进植物的养分运输、提高植物逆境生存能力等。然而，桉树种植对土壤AM真菌群落结构和功能的影响尚不清楚。研究比较了次生林改种桉树后不同年限（2年/5年/10年）的土壤理化性质、AM真菌种类、群落组成及多样性的变化。结果表明，桉树种植显著改变了土壤理化性质，具体表现为2年生和10年生桉树林中土壤pH和有机碳显著降低（P < 0.05）；AM真菌的孢子密度在桉树林土壤中显著低于次生林土壤（其中在5年生土壤中最低）；AM真菌的种丰度随种植年份的增加逐渐下降，在10年生桉树林土壤中有所恢复；5年生桉树的菌根侵染率最高，10年生桉树侵染率最低。AM真菌群落组成和结构发生显著变化，优势种Funneliforms geosporus的丰度在2年生和10年生林地中显著降低；而Septoglomus deserticola的丰度在2年生和10年生林地中显著增加。另外，冗余分析（Redundancy analysis，RDA）结果表明，土壤AM真菌群落结构主要受土壤pH值（解释率：89.88%）变化的影响。研究揭示了次生林改种桉树林后土壤AM真菌的群落变化特征，为桉树林的栽培管理和环境修复提供了数据支撑。 Abstract:Eucalyptus plantations are controversial because of its complexed impacts on environments. Arbuscular mycorrhizal (AM) fungi in soil provide important ecological functions such as enhancing soil nutrient transportation and plant stress tolerance via symbiosis. Until recently, the influence of massive Eucalyptus planting on soil microbial communities, especially the AM fungi is yet to be investigated. Herein, we investigated into these effects by comparing the diversity and taxonomic composition of AM fungal community in soil between the secondary forest and Eucalyptus forests which involved two-, five-, and ten-year's plantations. Our results provided evidence that the practices of Eucalyptus plantations significantly changed soil properties (P < 0.05), e.g., the soil pH and soil organic carbon significantly decreased in the two- and ten-year's soil samples relative to the secondary forest. Importantly, spore density of AM fungi in soil declined by the Eucalyptus plantations, with the lowest level being observed in the five-year plantation. Species richness of AM fungi inclined to decrease within five years of Eucalyptus plantation, but recovered to a contain extent after ten years. In contrast, AM infection rate on the roots of Eucalyptus reached to the highest and lowest level in the five-year and ten-year plantation, respectively. Further, the composition and structure of AM fungi shifted significantly by Eucalyptus plantations. Noticeably, the dominant species Funneliformis geosporus and Septoglomus deserticola significantly decreased and increased in the two- and ten-year Eucalyptus plantations, respectively. Lastly, our redundancy analysis indicated that soil pH largely promoted the variation of the AM fungal community (explanation rate: 89.88%). Collectively, our study revealed the shifts of AM fungi in the soil of the secondary forest after the practices of Eucalyptus plantations, which is necessary to shed light onto the strategies of environment restoration in Eucalyptus plantations. 参考文献 相似文献 引证文献

Soil constraints for arbuscular mycorrhizal fungi spore community in degraded sites of rupestrian grassland: Implications for restoration

The arbuscular mycorrhizal fungi (AMF) are important organisms with enormous potential for use in ecological restoration due to their positive association to seedlings. We evaluated the effects of soil degradation on a species-rich AMF community that could hinder the restoration of rupestrian grassland sites whose soil had been removed. Soil samples were taken from reference and degraded sites. We assessed the density, species richness, and composition of AMF, as well as soil macronutrients, metals, and texture. We found lower AMF density and richness in degraded than in reference sites. AMF community seemed to be negatively affected by a low level of potassium (K) and a higher concentration of heavy metals and clay in degraded sites. Besides the shifts in AMF composition associated mainly with K concentration, we found that the lack of this nutrient in degraded sites was also related to a significant reduction in density of AMF species, which are thought to play important roles in plant development and, therefore, in ecological restoration. Thus, we emphasize that efforts to restore degraded areas of rupestrian grassland should contemplate the reestablishment of soil physical and chemical properties, such as a lower clay concentration, and levels of nutrients that are key for AMF colonization. In addition, we suggest the further development of protocols for inoculation of seedlings and soil with AMF species to improve the success of replantation.

Abundance of rhizospheric bacteria and fungi associated with Fouquieria columnaris at Punta Cirio, Sonora, Mexico

A unique relictual population of Fouquieria columnaris is located in Sonora, along a 45-km strip of land encompassing Punta Cirio in the Sonoran Desert. The interaction of plants with microorganisms is an important adaptation to survival in desertic areas. The present study reports the abundance of bacteria, actinobacteria, and filamentous and arbuscular mycorrhizal fungi (AMF) in the rhizosphere of F. columnaris at Punta Cirio. Also, the genetic variability of F. columnaris was analyzed using amplied fragment length polymorphism markers. Bacteria and fungi in 27 soil samples from the rhizosphere of F. columnaris at 3 hills with low, medium, and high elevations were analyzed. The total bacterial, actinobacterial, and filamentous fungal counts did not differ among sites or elevations; no interaction between site and elevation was found. Nitrogen-fixing bacteria varied according to site but not elevation, whereas phosphorus-solubilizing bacteria were undetected. Filamentous fungi were dominated by Aspergillus spp. (48%) and Penicillium spp. (28%), which together represented 76% of the total average colony-forming units. The spore density of AMF ranged from 109 to 245 per 100 g of soil, and 65 to 80% of roots were colonized by hyphae, vesicles, or arbuscles of AMF. The DNA analysis generated an average similarity coefficient of 0.89, which could indicate high genetic homogeneity within the evaluated F. columnaris population.

Long-term grazing exclusion influences arbuscular mycorrhizal fungi and their association with vegetation in typical steppe of Inner Mongolia, China

It is not certain that long-term grazing exclusion influences arbuscular mycorrhizal (AM) fungi and their association with steppe vegetation. In this study, soil and plant samples were collected from two sites of grazing exclusion since 1983 (E83) and 1996 (E96), and one site of free-grazing (FG) in the typical steppe of Xilinguole League, Inner Mongolia, China, and assayed for soil basic physicochemical properties, AM fungal parameters, aboveground biomass and shoot phosphorus (P) uptake as well. The results showed that long-term grazing exclusion of E83 and E96 led to less drastic seasonal changes and significant increases in spore density, hyphal length density and root colonization intensity of AM fungi and even soil alkaline phosphatase activity, by up to 300, 168, 110 and 102%, respectively, compared with those of FG site. In addition, the total aboveground biomass and shoot P uptake of E83 and E96 were 75–992% and 58–645%, respectively, higher than those of FG. Generally, the root colonization intensity, spore density, and hyphal length density of AM fungi were all positively correlated with the aboveground biomass and even shoot P uptake of plant. These results may imply that grazing exclusion play a critical role in increasing the growth of AM fungi, and subsequently, may increase plant P uptake and aboveground biomass production. Moreover, the spore density could sensitively reflect the impacts of long-term grazing exclusion on AM fungi since survival strategy of spores in soil.

Inoculum effect of arbuscular mycorrhizal fungi on soybeans grown in long-term bare-fallowed field with low phosphate availability

ABSTRACTInoculation with arbuscular mycorrhizal fungi (AMF) can increase the growth of host plants, especially under condition of low phosphate (P) availability. Although this effect is shown relatively easily in simplified systems such as pot experiments, it is often hard to show in the field because of complicating factors such as competition with indigenous AMF. We conducted an AMF inoculation experiment with three Japanese soybean cultivars (Enrei, Misuzudaizu, and Akishirome) in an allophanic (Umbric Silandic) Andosol field under the long-term selective application of major nutrients (NPK and -P) and bare fallow. In the inoculation plots, introduced AMF were well colonized in soybean roots at flowering stage. In the -P plots, inoculation tended to increase the shoot dry weight of all the three soybean cultivars; this effect remained until harvest. Although a significant difference is not recognized, there was a tendency of residual effect on Enrei in the following year. In the NPK plots, inoculation did not significantly increase the shoot dry weight. We thought that in the -P plots, the long-term selective application of N and K and the long-term maintenance of bare fallow created the soil conditions of low P availability and poor native AMF. Thus, introduced AMF can benefit soybean growth and yield in the soil with low competitor AMF density and low phosphate availability.

Intercropping Maize With Legumes for Sustainable Highland Maize Production

Residue burning to prepare soil for maize growing deprives the soil of both protective cover and organic matter, and it exacerbates environmental issues such as Southeast Asia's haze problem. This paper reports on a study that evaluated the effectiveness of maize/legume intercropping as an alternative to maize cultivation with residue burning. Cowpea (Vigna unguiculata), mung bean (V. radiata), rice bean (V. umbellata), and lablab (Lablab purpureus) were sown into a standing maize crop 30 days before harvest, and the results were compared with a maize crop grown using residue burning as the method for land preparation at Pang Da Agricultural Station in Chiang Mai, Thailand, in a replicated trial conducted over 3 growing seasons from 2012 to 2014. Intercropping increased maize grain yield by 31–53% and left 70–170% more residue containing 113–230% more nitrogen than the maize sown after residue burning, depending on the legume, and decreased weed dry weight by two-thirds after 2 seasons. Soil biodiversity was enriched by the intercrops, with a doubling in the spore density of arbuscular mycorrhizal fungi in the root-zone soil and increased abundance, diversity (Shannon index), and richness of the soil macrofauna. The abundance of soil animals increased with crop residue dry weight (r = 0.90, P < 0.05) and nitrogen content (r = 0.98, P < 0.01). The effect of intercropping on maize grain yield and accumulation of residue and nitrogen were then confirmed in a participatory experiment involving farmers in 2 highland villages in the Phrao and Chiang Dao districts of Chiang Mai Province with maize and rice bean in 2015. The effects of maize/legume intercropping—increased nitrogen accumulation and crop residue, enhanced soil biodiversity, suppression of weeds, and protection of the soil surface, which enabled the maize to be sown without land clearing with fire—should all contribute to sustainable highland maize production.

Infection Unit Density as an Index of Infection Potential of Arbuscular Mycorrhizal Fungi.

The effective use of arbuscular mycorrhizal (AM) fungal function to promote host plant phosphate uptake in agricultural practice requires the accurate quantitative evaluation of AM fungal infection potential in field soil or AM fungal inoculation material. The number of infection units (IUs), intraradical fungal structures derived from single root entries formed after a short cultivation period, may reflect the number of propagules in soil when pot soil is completely permeated by the host root. However, the original IU method, in which all AM propagules in a pot are counted, requires the fine tuning of plant growing conditions and is considered to be laborious. The objective of the present study was to test whether IU density, not the total count of IU, but the number of IUs per unit root length, reflects the density of AM fungal propagules in soil. IU density assessed after 12 d of host plant cultivation and 3,3′-diaminobenzidine (DAB) staining showed a stronger linear correlation with propagule density than the mean infection percentage (MIP). In addition, IU density was affected less by the host plant species than MIP. We suggest that IU density provides a more rapid and reliable quantitation of the propagule density of AM fungi than MIP or the original IU method. Thus, IU density may be a more robust index of AM fungal infection potential for research and practical applications.

Influence of Long-Term Fertilization on Spore Density and Colonization of Arbuscular Mycorrhizal Fungi in a Brown Soil

This study aims to explore changes of long-term fertilization on spore density and colonization of AMF (Arbuscular mycorrhizal fungi) under a 38-y long-term fertilization in a brown soil. Soil samples (0-20 cm,20-40cm,40-60cm)were taken from the six treatments of the long-term fertilization trial in October 2016:no fertilizer (CK), N1(mineral nitrogen fertilizer), N1P (mineral nitrogen and phosphate fertilizer), N1PK (mineral nitrogen, phosphate and potassic fertilizer), pig manure (M2), M2N1P (pig manure, mineral nitrogen andphosphate fertilizer).Spores were isolated from soils by wet sieving and sucrose density gradient centrifugation; mycorrhizal colonization levels were determined by the gridline intersect. The spore density was highest in the topsoils (0-20 cm), and was decreased with increasing of soil depth in each treatment. The spores density of M2N1P treatment was significantly higher than that of other treatments in each soil layer. Application of inorganic fertilizer (especially inorganic with organic fertilizer) can greatly improve the level of colonization. Our results suggested that long-term fertilization significantly affects spore density and colonization of AMF, however, spore density is not related to colonization rate.

Spore Density of Arbuscular Mycorrhizal Fungi is Fostered by Six Years of a No-Till System and is Correlated with Environmental Parameters in a Silty Loam Soil

Arbuscular mycorrhizal fungi (AMF) play major roles in nutrient acquisition by crops and are key actors of agroecosystems productivity. However, agricultural practices can have deleterious effects on plant–fungi symbiosis establishment in soils, thus inhibiting its potential benefits on plant growth and development. Therefore, we have studied the impact of different soil management techniques, including conventional moldboard ploughing and no-till under an optimal nitrogen (N) fertilization regime and in the absence of N fertilization, on AMF spore density and soil chemical, physical, and biological indicators in the top 20 cm of the soil horizon. A field experiment conducted over six years revealed that AMF spore density was significantly lower under conventional tillage (CT) combined with intensive synthetic N fertilization. Under no-till (NT) conditions, the density of AMF spore was at least two-fold higher, even under intensive N fertilization conditions. We also observed that there were positive correlations between spore density, soil dehydrogenase enzyme activity, and soil penetration resistance and negative correlations with soil phosphorus and mineral N contents. Therefore, soil dehydrogenase activity and soil penetration resistance can be considered as good indicators of soil quality in agrosystems. Furthermore, the high nitrate content of ploughed soils appears to be detrimental both for the dehydrogenase enzyme activity and the production of AMF spores. It can be concluded that no-till, by preventing soil from structural and chemical disturbances, is a farming system that preserves the entire fungal life cycle and as such the production of viable spores of AMF, even under intensive N fertilization.

Spatiotemporal variation of arbuscular mycorrhizal fungal colonization in olive (Olea europaea L.) roots across a broad mesic-xeric climatic gradient in North Africa.

This study aims to determine the spatiotemporal dynamics of root colonization and spore density of arbuscular mycorrhizal fungi (AMF) in the rhizosphere of olive trees (Olea europaea) with different plantation ages and under different climatic areas in Algeria. Soil and root samples were seasonally collected from three olive plantations of different ages. Other samples were carried out in productive olive orchards cultivated under a climatic gradient (desertic, semi-arid, subhumid, and humid). The olive varieties analysed in this study were Blanquette, Rougette, Chemlel and the wild-olive. Spore density, mycorrhization intensity (M%), spore diversity and the most probable number (MPN) were determined. Both the intensity of mycorrhizal colonization and spore density increased with the increase of seasonal precipitation and decreased with the increase of air temperature regardless of the climatic region or olive variety. The variety Rougette had the highest mycorrhizal levels in all plantation ages and climates. Spore community was composed of the genera Rhizophagus, Funneliformis, Glomus, Septoglomus, Gigaspora, Scutellospora and Entrophospora. The genus Glomus, with four species, predominated in all climate regions. Spores of Gigaspora sp. and Scutellospora sp. were the most abundant in desertic plantations. Statistical models indicated a positive relationship between spore density and M% during spring and winter in young seedlings and old plantations. A significant positive relationship was found between MPN and spore density under different climates. For a mycotrophic species, the rhizosphere of olive trees proved to be poor in mycorrhiza in terms of mycorrhizal colonization and numbers of the infective AMF propagules.

The Effect of Distance from River on Soil Physiochemical Properties, Root Colonization and Spore density of Arbuscular Mycorrhizal Fungi Associated with Salt Cedar

The Effect of Distance from River on Soil Physiochemical Properties, Root Colonization and Spore density of Arbuscular Mycorrhizal Fungi Associated with Salt Cedar

Arbuscular Mycorrhizal Fungi spores diversity and AMF infection in some medicinal plants of District Charsadda KPK

An investigation has been made about the Arbuscular Mycorrhizal Fungi (AMF) spore population and root colonization in 20 medicinal plants selected and collected from district Charsadda at early winter and summer seasons during session 2014-2015. The spore density of AMF ranged from 80 spores per 100gm -1 , and root colonization from 20-80%. The lowest spore density was recorded in Cestrum nocturnum, Ficus carica, Aquilaria agallocha and the highest spore density was recorded in Sedum dendroideum, Cannabis sativa, Triticum aestivum, and Mentha longifolia, Withania somnifera while absent in Brassica campestris, Amaranthus viridis. The spore density of AMF and root colonization by these fungi varied from species to species, season to season, and also affected by host plant growth stages (vegetative-fruiting).AM fungi association was more observed at fruiting stage and low at vegetative and flowering phases of host. The most dominant species of AMF were Glomus followed by Sclerocystis and Acaulospora species.

Responses of above- and below-ground fungal symbionts to cessation of mowing in subalpine grassland

Abstract The cessation of mowing in subalpine grasslands promotes the dominance of Festuca paniculata leading to the reduction in plant diversity. Moreover, it affects positively the abundance of Epichloe sp. inhabiting F. paniculata leaves and negatively the soil density of arbuscular mycorrhizal fungi (AMF). We explored how the cessation of mowing influences root AMF communities in F. paniculata and the neighboring plants, and Epichloe sp alkaloids. Thirteen AMF operational taxonomical units were found. The neighboring plants affected positively the abundances of Aalpin and GLOM_7 whereas the interaction plant/management type influenced significantly Claroide_1 , GLOM_1 and GLOM_7 . The N-formylnorloline, produced by Epichloe sp. increased in unmown grassland. Hence, the cessation of mowing, coinciding with the high abundance of endophyte alkaloid, affected root-associated AMF with differential responses at the abundance level. The N-formylnorloline could be one compound underpinning the dynamic of plant diversity with a resulting structuration of AMF in subalpine grasslands.

Integrating Faidherbia albida trees into a sorghum field reduces striga infestation and improves mycorrhiza spore density and colonization

Integrating agroforestry trees such as Faidherbia albida (F. albida) into cropland improves soil fertility and maintains persistence of associated beneficial microorganisms such as Arbuscular Mycorrhizal Fungi (AMF) that protects crops from striga colonization. Striga hermonthica (striga) is an obligate root hemi-parasitic weed of maize and sorghum, which stunts growth and causes low grain yield. Data on physico-chemical properties of the soil, yield components of sorghum, striga infestation and spore abundance and colonization of AM fungi were collected from underneath and away from the F. albida canopy. The experiment was composed of four treatments and six replications in a randomized complete block design (RCBD) with 24 plots, each with 15 m2 size. Soil and root samples were also collected from under and outside of the F. albida canopy and sorghum crops. Soil organic matter, total N, available P, CEC, and total K were significantly higher under the F. albida canopy than away from it (P < 0.05). Similarly, yield of sorghum was also significantly higher under the F. albida canopy than away from it (P < 0.05). The highest striga count was recorded away from the F. albida canopy. In contrast, minimal striga infestation was found under and at the periphery of the F. albida canopy. The spore density and colonization of AMF were higher under and at the periphery of the F. albida canopy than away from it (P < 0.05). There was a significant and negative correlation between AMF fungi spore density and colonization, and striga counts at the early stage of sorghum growth. Integrating F. albida into agricultural fields with sorghum crops improves productivity and maintains AM inoculum which may control striga weed infestation.

Consequences of inoculation with native arbuscular mycorrhizal fungi for root colonization and survival of Artemisia tridentata ssp. wyomingensis seedlings after transplanting.

In arid environments, the propagule density of arbuscular mycorrhizal fungi (AMF) may limit the extent of the plant-AMF symbiosis. Inoculation of seedlings with AMF could alleviate this problem, but the success of this practice largely depends on the ability of the inoculum to multiply and colonize the growing root system after transplanting. These phenomena were investigated in Artemisia tridentata ssp. wyomingensis (Wyoming big sagebrush) seedlings inoculated with native AMF. Seedlings were first grown in a greenhouse in soil without AMF (non-inoculated seedlings) or with AMF (inoculated seedlings). In spring and fall, 3-month-old seedlings were transplanted outdoors to 24-L pots containing soil from a sagebrush habitat (spring and fall mesocosm experiments) or to a recently burned sagebrush habitat (spring and fall field experiments). Five or 8months after transplanting, colonization was about twofold higher in inoculated than non-inoculated seedlings, except for the spring field experiment. In the mesocosm experiments, inoculation increased survival during the summer by 24% (p = 0.011). In the field experiments, increased AMF colonization was associated with increases in survival during cold and dry periods; 1year after transplanting, survival of inoculated seedlings was 27% higher than that of non-inoculated ones (p < 0.001). To investigate possible mechanisms by which AMF increased survival, we analyzed water use efficiency (WUE) based on foliar (13)C/(12)C isotope ratios (δ (13)C). A positive correlation between AMF colonization and δ (13)C values was observed in the spring mesocosm experiment. In contrast, inoculation did not affect the δ (13)C values of fall transplanted seedlings that were collected the subsequent spring. The effectiveness of AMF inoculation on enhancing colonization and reducing seedling mortality varied among the different experiments, but average effects were estimated by meta-analyses. Several months after transplanting, average AMF colonization was in proportion 84% higher in inoculated than non-inoculated seedlings (p = 0.0042), while the average risk of seedling mortality was 42% lower in inoculated than non-inoculated seedlings (p = 0.047). These results indicate that inoculation can increase AMF colonization over the background levels occurring in the soil, leading to higher rates of survival.

Influence of season and edaphic factors on endorhizal fungal associations in subtropical plantation forest trees of Northeastern India

Investigations on arbuscular mycorrhizal (AM) and dark septate endophyte (DSE) fungi are limited in trees of subtropical forests compared to other terrestrial ecosystems. We assessed the seasonal dynamics of endorhizal fungal symbioses in four dominant tree species (Alnus nepalensis, Castanopsis hystrix, Emblica officinalis, Schima wallichii) in two plantation forest stands of Northeastern India, a biodiversity hotspot part of the Indo-Burma region. All tree species examined had a dual association of AM and DSE fungi and such fungal symbioses are reported for the first time in A. nepalensis, C. hystrix and S. wallichii. Intermediate-type AM morphology was common in three tree species, while Paris-type AM morphology was found in S. wallichii. Colonization of AM and DSE fungi varied significantly across tree species and seasons. A total of 18 AM fungal spore morphotypes were isolated from the air-dried natural rhizosphere soils and trap culture experiments. Spore density of AM fungi was highest in summer, whereas AM colonization in roots was highest during the rainy season. In contrast, root colonization with DSE fungi was highest during summer, except for E. officinalis. A significant negative correlation occurred between certain AM fungal and soil variables. In contrast, DSE fungal measures were not correlated to any of the soil properties examined. Correlation analysis indicated a certain degree of competition between AM and DSE fungi. Occurrence of AM and DSE fungal associations in economically important indigenous tree species indicates the possibility of utilizing them in future conservation programs.

Mycorrhizal colonization and diversity and corn genotype yield in soils of the Cerrado region, Brazil

The degree of interaction between arbuscular mycorrhizal fungi (AMF) and host plants appears to depend on plant genotype, which differentially promotes symbiosis and leads to different degree of mycotrophism. The aim of the present study was to assess root colonization, spore density, and diversity of AMF, as well as yield of corn (Zea mays) genotypes in soil from the Cerrado region of Brazil. Number of spores (NS), mycorrhizal colonization (COL), plant and ear height, dry weight (DW), and grain yield (GY) were assessed in inbred lines and their hybrids. Randomized blocks were used for the experimental design, with 30 treatments (genotypes) and three repetitions. The experiment was conducted on the farm of the UNESP-São Paulo State University, Campus of Ilha Solteira, and the plots were composed of two 2-m-long rows, with 0.85 m between rows, and 0.20 m between plants. Qualitative and quantitative changes were observed in fungal compositions, as well as preferential associations between symbiotic partners. Analysis of AMF diversity revealed the presence of 12 species, with Scutellospora calospora and Entrophospora colombiana being the most abundant in all treatments. The species Acaulospora longula, Glomus etunicatum, Glomus macrocarpum, and Gigaspora margarita exhibited preferential associations with certain genotypes. COL and GY differed among inbred lines and single-cross hybrids and the significant correlations between COL and the DW and GY showed positive interactions between the plants and AMF. There was no correlation between heterosis for GY and heterosis for colonization. These single-cross hybrids HS83 × E3 and D3 × F5 exhibited high GY, evidencing a productivity potential for the low technological condition used.

Mycorrhizal colonization and diversity and corn genotype yield in soils of the Cerrado region, Brazil

&lt;p&gt;The degree of interaction between arbuscular mycorrhizal fungi (AMF) and host plants appears to depend on plant genotype, which differentially promotes symbiosis and leads to different degree of mycotrophism. The aim of the present study was to assess root colonization, spore density, and diversity of AMF, as well as yield of corn (&lt;em&gt;Zea mays) &lt;/em&gt;genotypes in soil from the Cerrado region of Brazil. Number of spores (NS), mycorrhizal colonization (COL), plant and ear height, dry weight (DW), and grain yield (GY) were assessed in inbred lines and their hybrids. Randomized blocks were used for the experimental design, with 30 treatments (genotypes) and three repetitions. The experiment was conducted on the farm of the UNESP-São Paulo State University, Campus of Ilha Solteira, and the plots were composed of two 2-m-long rows, with 0.85 m between rows, and 0.20 m between plants. Qualitative and quantitative changes were observed in fungal compositions, as well as preferential associations between symbiotic partners. Analysis of AMF diversity revealed the presence of 12 species, with &lt;em&gt;Scutellospora calospora &lt;/em&gt;and &lt;em&gt;Entrophospora colombiana &lt;/em&gt;being the most abundant in all treatments. The species &lt;em&gt;Acaulospora longula&lt;/em&gt;, &lt;em&gt;Glomus etunicatum&lt;/em&gt;, &lt;em&gt;Glomus macrocarpum, &lt;/em&gt;and &lt;em&gt;Gigaspora margarita &lt;/em&gt;exhibited preferential associations with certain genotypes. COL and GY differed among inbred lines and single-cross hybrids and the significant correlations between COL and the DW and GY showed positive interactions between the plants and AMF. There was no correlation between heterosis for GY and heterosis for colonization. These single-cross hybrids HS83 × E3 and D3 × F5 exhibited high GY, evidencing a productivity potential for the low technological condition used.&lt;/p&gt;

Disease ecology across soil boundaries: effects of below-ground fungi on above-ground host-parasite interactions.

Host-parasite interactions are subject to strong trait-mediated indirect effects from other species. However, it remains unexplored whether such indirect effects may occur across soil boundaries and connect spatially isolated organisms. Here, we demonstrate that, by changing plant (milkweed Asclepias sp.) traits, arbuscular mycorrhizal fungi (AMF) significantly affect interactions between a herbivore (the monarch butterfly Danaus plexippus) and its protozoan parasite (Ophryocystis elektroscirrha), which represents an interaction across four biological kingdoms. In our experiment, AMF affected parasite virulence, host resistance and host tolerance to the parasite. These effects were dependent on both the density of AMF and the identity of milkweed species: AMF indirectly increased disease in monarchs reared on some species, while alleviating disease in monarchs reared on other species. The species-specificity was driven largely by the effects of AMF on both plant primary (phosphorus) and secondary (cardenolides; toxins in milkweeds) traits. Our study demonstrates that trait-mediated indirect effects in disease ecology are extensive, such that below-ground interactions between AMF and plant roots can alter host-parasite interactions above ground. In general, soil biota may play an underappreciated role in the ecology of many terrestrial host-parasite systems.

Occurrence and Structure of Arbuscular Mycorrhizal Fungal Communities in Cassava after Cultivation of Cover Crops as Observed by the “PCR-DGGE” Technique

ABSTRACT Cassava (Manihot esculenta Crantz) is a highly mycotrophic crop, and prior soil cover may affect the density of arbuscular mycorrhizal fungi (AMFs), as well as the composition of the AMFs community in the soil. The aim of this study was to evaluate the occurrence and the structure of AMFs communities in cassava grown after different cover crops, and the effect of the cover crop on mineral nutrition and cassava yield under an organic farming system. The occurrence and structure of the AMFs community was evaluated through polymerase chain reaction (PCR) and denaturing gradient gel electrophoresis (DGGE). A randomized block experimental design was used with four replications. Six different cover crop management systems before cassava were evaluated: black oats, vetch, oilseed radish, intercropped oats + vetch, intercropped oats + vetch + oilseed radish, plus a control (fallow) treatment mowed every 15 days. Oats as a single crop or oats intercropped with vetch or with oilseed radish increased AMFs inoculum potential in soil with a low number of propagules, thus benefiting mycorrhizal colonization of cassava root. The treatments did not affect the structure of AMFs communities in the soil since the AMFs communities were similar in cassava roots in succession to different cover crops. AMFs colonization was high despite high P availability in the soil. The cassava crop yield was above the regional average, and P levels in the leaves were adequate, regardless of which cover crop treatments were used. One cover crop cycle prior to the cassava crop was not enough to observe a significant response in variables, P in plant tissue, crop yield, and occurrence and structure of AMFs communities in the soil. In the cassava roots in succession, the plant developmental stage affected the groupings of the structure of the AMF community.