Diversity of arbuscular mycorrhizal fungi in greenhouse soils continuously planted to watermelon in North China

Seasonal variation in winter wheat field soil arbuscular mycorrhizal fungus communities after non-mycorrhizal crop cultivation

Intensive farming practices that implement deep and frequent tillage, high input inorganic fertilization, cultivation with non-host species, and pesticide use are widely reported to be detrimental for arbuscular mycorrhizal fungi (AMF), which are one of the most important plant biofertilizers. The effect of the reduction of agricultural input on AMF community dynamics following conversion from conventional non-mycorrhizal to lower input mycorrhizal crop cultivation has not yet been fully elucidated. We investigated the effect of the reduction of agricultural input, rotation, and season on AMF communities in winter wheat field soil after conversion from long-term (more than 20 years) non-mycorrhizal (sugar beet) crop cultivation. We described AMF communities from bulk soil samples by specifically targeting the 18S ribosomal gene using a combination of AMF specific primers and 454 pyrosequencing. No effect was found after 3 years' reduction of agricultural input, and only marginal effects were due to rotation with specific crops preceding winter wheat. Instead, season and year of sampling had the most appreciable influence on the AMF community. We suggest that, after conversion from long-term non-mycorrhizal to mycorrhizal crop cultivation, AMF diversity is low if compared to similar agroecosystems. Seasonal and successional dynamics play an important role as determinants of community structure.

Differences in Arbuscular Mycorrhizal Fungal Community Composition in Soils of Three Land Use Types in Subtropical Hilly Area of Southern China

Land use type is key factor in restoring the degraded soils due to its impact on soil chemical properties and microbial community. In this study, the influences of land use type on arbuscular mycorrhizal fungal (AMF) community and soil chemical properties were assessed in a long-run experimental station in subtropical hilly area of southern China. Soil samples were collected from forest land, orchard and vegetable field. Soil chemical properties were analyzed, and PCR-DGGE was performed to explore the AMF community structure. Cloning and sequencing of DGGE bands were conducted to monitor AMF community composition. Results indicate that the contents of total P, available P and available K were the highest while the contents of soil organic matter, total N, total K and available N were the lowest in vegetable field soils, with forest land soils vice versa. According to DGGE profiling, AMF community in forest soils was more closely related to that in orchard soils than that in vegetable field soils. Sequencing indicated that 45 out of 53 excised bands were AMF and 64.4% of AMF belonged to Glomeraceae, including some “generalists” present in all soils and some “specialists” present only in soils of particular land use. Category principle component analysis demonstrated that total N, soil organic matter and available P were the most important factors affecting AMF community, and some AMF phylotypes were closely associated with particular soil chemical properties. Our data suggest that AMF communities are different with different land use types.

Arbuscular mycorrhizal fungi community structure, abundance and species richness changes in soil by different levels of heavy metal and metalloid concentration

Arbuscular Mycorrhizal Fungi (AMF) play major roles in ecosystem functioning such as carbon sequestration, nutrient cycling, and plant growth promotion. It is important to know how this ecologically important soil microbial player is affected by soil abiotic factors particularly heavy metal and metalloid (HMM). The objective of this study was to understand the impact of soil HMM concentration on AMF abundance and community structure in the contaminated sites of South Korea. Soil samples were collected from the vicinity of an abandoned smelter and the samples were subjected to three complementary methods such as spore morphology, terminal restriction fragment length polymorphism (T-RFLP) and denaturing gradient gel electrophoresis (DGGE) for diversity analysis. Spore density was found to be significantly higher in highly contaminated soil compared to less contaminated soil. Spore morphological study revealed that Glomeraceae family was more abundant followed by Acaulosporaceae and Gigasporaceae in the vicinity of the smelter. T-RFLP and DGGE analysis confirmed the dominance of Funneliformis mosseae and Rhizophagus intraradices in all the study sites. Claroideoglomus claroideum, Funneliformis caledonium, Rhizophagus clarus and Funneliformis constrictum were found to be sensitive to high concentration of soil HMM. Richness and diversity of Glomeraceae family increased with significant increase in soil arsenic, cadmium and zinc concentrations. Our results revealed that the soil HMM has a vital impact on AMF community structure, especially with Glomeraceae family abundance, richness and diversity.

Mycorrhizal responsiveness of maize (Zea mays L.) genotypes as related to releasing date and available P content in soil

The aim of this study was to compare the mycorrhizal responsiveness among old and recent Chinese maize genotypes (released from 1950s to 2008) in low- and high-Olsen-P soils and to identify parameters that would indicate the relationships between the mycorrhizal responsiveness and the functional traits related to P uptake of maize. A greenhouse factorial experiment was conducted. The factors were maize genotype [Huangmaya (HMY), Zhongdan 2 (ZD2), Nongda 108 (ND108), and NE15], inoculation with or without arbuscular mycorrhizal fungi (AMF) (Rhizophagus irregularis), and Olsen-P levels (4, 9, 18, 36, or 60 mg P kg(-1)). Old and recently released genotypes differed in their response to AMF under low- and high-P supply. Three kinds of responses (in terms of shoot growth) were observed: the response was positive if the soil P content was low, but negative if the soil Olsen-P content was high (HMY and ND108); the response was neutral regardless of soil P content (ZD2); and the response was positive regardless of soil P content (NE15). Principle component (PC) analysis showed that the first PC comprised morphological and physiological traits of maize roots, and the second PC comprised mycorrhizal traits. The opposite was the case, however, in high-P soil. It is concluded that maize breeding selection from 1950s to 2000s is not always against the AM association and that AMF play positive roles in promoting the growth of some maize genotypes in high-P soil. The root length colonization by efficient AMF might be a useful parameter for breeding varieties with increased mycorrhizal responsiveness.