Effects of applying vitamin B₆ to soil on soil microbial diversity of apple orchard

Objectives Microorganisms in soil are important factors affecting root environment, and vitamin B₆ can improve fruit quality. This study discussed how vitamin B₆ affected soil microbial diversity by means of high-throughput sequencing to reveal the mechanism of improving the soil quality.

Methods In April 2015, different does of vitamin B₆ were applied to Fuji apple root soil 1 meter away from tree trunk. In October 2015, soil samples were collected in the area with vitamin B₆, genomic DNA was extracted, and PCR amplification was made to establish libraries. The 16S rRNA genes V4+V5 regions of soil bacteria and fungal ITS1+ITS2 regions were sequenced by high-throughput sequencing technology, and related biological analysis was conducted to explore the changes of soil bacterial and fungal abundances, diversities and structures.

Results According to the result of high-throughput sequencing technology, a total of 530714 bacteria effective tags and 434886 fungus effective tags were obtained from 9 soil samples. Also a total of 1920 bacterial operational taxonomic units(OTUs) and 374 fungi OTUs were gotten from each soil sample on average, and 566 bacterial OTUs and 73 fungi OTUs were identical in each soil sample. The richness indices of Ace and Chao showed that the treatment of vitamin B₆ 5 g/plant increased the abundance of soil bacteria, the indices of Ace was improved by 62.6% and the indices of Chao improved by 71.6% remarkably, and the abundance of soil fungi was reduced, the indices of Chao was reduced by 18.6% remarkably. The treatment of vitamin B₆ 10 g/plant had no obvious effect on the abundance of soil bacteria and fungi. The analysis showed that the treatment of vitamin B₆ 5 g/plant increased the diversity of soil bacteria, the indices of Shannon was improved by 22.3%, and the diversity of soil fungi was reduced, the indices of Shannon was reduced by 29.2% and the indices of Shannon was reduced by 34.4% remarkably; the treatment of vitamin B₆10 g/plant had no obvious effect on the diversity of soil bacteria and fungi. On the classification level of phylum, Proteobacteria, Actinobacteria, Bacteroidetes, Acidobacteria were the dominant bacteria with the total relative abundance over 80%. And Ascomycota, Basidiomycota, Zygomycota were dominant fungi with the total relative abundance over 98%. The treatment of 5 g/plant reduced the relative abundance of Bacteroidetes, increased the relative abundance of Ascomycota and reduced the relative abundance of Basidiomycota and Zygomycota. And the treatment of vitamin B₆ 10 g/plant increased the relative abundance of Proteobacteria and Actinobacteria, reduced the relative abundance of Bacteroidetes and Acidobacteria, increased the relative abundance of Ascomycota and reduced the relative abundance of Basidiomycota and Zygomycota.

Conclusions As a good way of root ecological regulation, vitamin B₆ has excellent popularization significance by changing the abundance and diversity of soil bacteria and fungi and the classification level of phylum.