Effects of different crop rotation modes on fungal community in potato rhizosphere soil

【Objective】The purpose of this study was to reveal the distribution features of fungi in potato rhizosphere soil when bacterial disease occurred or not in paddy-upland rotation mode and upland rotation mode, respectively, so as to provide reference for soil health management and sustainable potato production.【Method】The rhizosphere soil samples of healthy potato plants/plants with bacterial disease were collected in upland rotation and paddy-upland rotation modes, respectively. The rhizosphere soil samples of healthy potato plants in upland rotation and paddy-upland rotation were labeled as HD.J and SH.J, respectively, and those of plants with bacterial disease in upland rotation and paddy-upland rotation were labeled as HD.B and SH.B, respectively. Using Illumina high-throughput sequencing platform, the fungal ribosomal DNA internal transcribed spacer 1(ITS1) was analyzed to compare the distribution characteristics of fungal communities in rhizosphere soil in two rotation modes.【Result】The composition and diversity of fungal community in rhizosphere soil of healthy potato plants were similar in the two rotation patterns. Principal coordinate analysis also showed that the distance between the fungal community structure of HD.J and SH.J was close. For known phyla of HD.J and SH.J, Ascomycota and Basidiomycota were the dominant phyla. Among the known fungal communities, the relative abundance of Ascomycota was 33.0% and 30.0%, and that of Basidiomycota was 3.8% and 9.6% in HD.J and SH.J, respectively. The phyla of HD.J and SH.J were mainly unknown fungi, accounting for 63.0% and 60.0%, respectively. Hypocreales, Helotiales, Pleosporales and Sordariales belonging to Ascomycota and Agaricales belonging to Basidiomycota were the common dominant orders of both HD.J and SH.J, which might be the core group of potato rhizosphere soil fungal community. When potato bacterial disease occurred, the fungal community Alpha-diversity of the two rotation patterns was HD.B>SH.J>HD. J>SH.B. The relative abundances of Basidiomycota of HD.B and SH.B were higher than those of HD.J and SH.J. Among them, the abundance of Geastrales was up to 82.8% in SH.B while the abundance of Tremellales was 18.6% in HD.B. Two dominant genera in HD.B were Verticillium, which could cause Verticillium wilt of potato, and Nakataea, which could cause sclerotinia and stalk rot of rice, with abundance of 6.8% and 5.9% respectively. Using FUNGuild database for prediction of fungal trophic modes, comparing that there was only one trophic mode, pathotroph, was dominant in HD.J (20.6% relative abundance), there were dominant modes, pathotroph, saprotroph, and pathotroph-saprotroph-symbiotroph in HD.B(with 15.4%, 18.8% and 21.4% of relative abundance, respectively). The relative abundances of saprotroph in SH.J and SH.B were 28.2% and 10.2%, respectively, and the total abundances of other trophic modes were 4.6% and 4.9%.【Conclusion】The dominant fungal populations in potato rhizosphere soil in the two rotation patterns remain stable, which suggests that they may be the core group of rhizosphere fungi and they are of great significance to maintain the healthy growth of potato. Upland rotation mode may be more conducive to the accumulation of pathotroph fungi. Diseased potato may be more conducive to the accumulation of saprotroph fungi. It is important to remove diseased plant residues in time in order to restore the microecosystem balance of soil.