Function and Characterization of Fungal Communities in Chestnut Soils (Castanea crenata) of Kansai Region, Japan

Chestnut (Castanea crenata) is an important fruit crop in Japan, grown under three cultivation systems in Kansai region, which succumb to fungal root disease pathogens. The fungal community in soils of chestnut in these cultivation systems were characterized along with the potential of soil bacterial species as biological control agent against these root-invading fungi. Bacteria from the chestnut soil rhizosphere were identified and their ability to suppress diseases in vitro was evaluated. Bacteria DAC17225011 and DAC17225014 showed 99% similarity to Bacillus aryabhattai and Pseudomonas frederiksbergensis, respectively, which could suppress the growth of Armilaria mellea and Phytophtora cambivora, respectively, in vitro conditions. The assay in vivo indicated the positive effect of these bacteria on the reduction of disease infection spots in chestnut roots; however, no visible symptoms were detected aboveground. For microbial community analysis, chestnut soil was sampled from four locations (Wachi, Ayabe, Fukuchiyama and Sasayama) considering three management systems, conventional, organic and wild. The amplicon from the ITS region (The genomic library of the fungal detection in soils) was sequenced by Illumina MiSeq 250bp and used to analyze the fungal community in the sampled soil. Nectriaceae, which contains pathogenic fungi, was very common in all samples, but lower in wild areas. Ceratobasidiacea was also higher in conventional areas. For the symbiotic families, Hypocraceae and Russulaceae were typical in wild soils, whereas Amanitaceae was found in organic soils. The fungal community was clearly distinct in the wild system, differing from conventional and organic systems.