Colonization of plant roots by arbuscular mycorrhizal (AM) fungi is a primary factor determining mycorrhizal associations. This study aimed to investigate the variation in AM colonization among maize genotypes and in response to plant breeding programs. Three types of maize (Zea mays) germplasms composed of 141 inbred lines, 38 hybrids, and 76 landraces were grown in replicated field experiments in Sapporo, Japan, for two cropping years to evaluate the percentage of root length colonized by indigenous AM fungi. The percent colonization varied greatly and continuously among maize genotypes. Inbred lines that originated (released) in particular locations (e.g., Tokachi, Japan) and years (e.g., 1960s) showed significantly larger values than other lines. Inter-location differences were also observed for landraces. The direction of the year-ofrelease effect on colonization depended on the origin. No significant differences were observed between leaf-blight-disease-resistant near-isogenic inbred lines and their parents. Modern hybrids showed significantly greater values than inbred lines and older landraces. Evaluating numerous, diverse genotypes demonstrated that AM colonization of maize plants varies with germplasm type, origin (country and location), and year of release, and that modern plant breeding programs do not necessarily lead to the suppression of colonization.

Acid sulfate soil has an extremely low pH and revegetation of the soil is difficult because of the high concentration of toxic elements, such as aluminum, and poor nutrient availability. Community compositions of arbuscular mycorrhizal (AM) fungi that associate with Miscanthus sinensis, a pioneer grass species that occurs in acid sulfate soil, were investigated to clarify the environmental factors that regulate the community structure. The rhizosphere soils of M. sinensis growing in acid sulfate soils were collected from three sites distributed in subarctic, temperate and subtropical zones. Rhizosphere soils of plants growing in a sandy soil site in a subarctic zone were also collected. Miscanthus sinensis seedlings were grown on these soils in a greenhouse for 2 months and a large subunit ribosomal RNA gene of the fungi was amplified from DNA extracted from the roots. Based on the nucleotide sequences of the gene, 20 phylotypes across six genera were detected from the four sites. The similarity indices of AM fungal communities among the sites did not correlate with geographical distance. Ordination analysis (principal component analysis) on the communities suggested that the first principal component reflected edaphic factors, particularly soil pH. Plotting of soil pH data at which respective phylotypes occurred and subsequent statistical analysis revealed that the ranges of preferential pH were significantly different among the phylotypes. The distribution of AM fungal phylotypes along pH gradients was further recognized by plotting the first principal component scores of the phylotypes against their preferential pH. The phylotypes that showed higher scores along the second principal component were detected from three or more sites and occurred over a wide range of pH values. These observations suggest that the preference and range of substrate pH to which the fungi can adapt are different among the phylotypes and soil pH might be a likely driving force for structuring AM fungal communities in acid sulfate soils.

As a kind of excellent diesel-blending component, polyoxymethylene dimethyl ethers (PODEn) have received widespread attention. Herein, Al-SBA-15 molecular sieves with different Si/Al ratios and pore sizes were synthesized and used to investigate the catalytic performance for the synthesis of polyoxymethylene dimethyl ethers from methylal and trioxane. X-ray diffraction, N 2 adsorption−desorption, scanning electron microscopy, transmission electron microscopy, X-ray fluorescence, and 27 Al NMR were used to characterize the structures of obtained catalysts. Ammonia temperature-programmed desorption and pyridine adsorption were carried out to investigate the acid properties of the catalysts. Through comparison of the catalysts with different Al contents, it was found that the relatively weak acid was more suitable for the synthesis of PODEn than the relatively strong acid in the catalytic system of Al-SBA-15. On the Al-SBA-15(2)-150 catalyst, which has only a weak acid of 0.163 mmol/g, the highest TOX conversion rate and highest PODEn yield and selectivity were achieved, showing the best catalytic performance. It appears that the PODEn synthesis can be catalyzed by not only a Bronsted acid but also a Lewis acid. The catalysts with strong acid and/or with a large number of acids will cause the generation of significant amount of methyl formate byproduct. Through comparison of the catalysts with different pore sizes, it was found that a relative larger pore size of the catalyst was beneficial for the PODEn synthesis to a certain extent under the catalysts with strong acid and/or large acid amount, but on the catalyst that had only weak acid and a relatively lesser amount, the change of pore size had almost no effect on the yield and selectivity of PODEn products.

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