Assessment of variation in paddy microbial communities under different storage temperatures and relative humidity by Illumina sequencing analysis

Temperature and relative humidity are important conditions in paddy storage; however, their influence on microbial communities in stored paddy remains poorly understood. In this study, paddy was stored at different temperatures and relative humidity, and severe mildew was observed in samples stored at relative humidity of 97% and different temperatures (15, 28, and 37 °C) after 50 days. High-throughput 16S rRNA and ITS genes amplicon sequencing analyses showed that Proteobacteria, Firmicutes, and Ascomycota were the dominant phyla across the paddy samples. Moreover, Staphylococcus in bacteria and Aspergillus in fungi were predominant in the composition of microbial community among mildewed paddy samples. The maximum abundance of the two types of organisms appeared in samples stored at 37 °C and relative humidity of 97% (T37H97; 85.02 ± 9.77%), and 15 °C and relative humidity of 97% (T15H97; 93.60 ± 0.01%), respectively. In addition, the two genera were also found in mildew from spoiled paddy by using plate isolation method, revealing their important role in paddy spoilage. Statistical analysis indicated that relative humidity was the most important factor affecting the relative abundances of microbial communities and had the 38.98% and 15.74% contributions to the variation of bacterial and fungal communities, respectively. Hence these results could be very conducive to the promotion of safe storage of paddy.