Abstract:

This research explored the effects of fungal diseases of silage maize on microbial diversity and community structure of maize silage during fermentation. Fermentation of maize silage without any disease （CK） was compared with that of silage maize infected by Alternaria leaf spot disease （YLG）， Bipolaris sorokiniana leaf spot disease （YM）， Ustilago maydis silage maize （YL） and common rust （YX）， with three replicates per treatment. After 40 days of silage fermentation， Illumina amplicon sequencing technology was used to analyze the fungal and bacterial diversity of microbial communities in each sample. The analysis revealed that the microbial structure of silage maize samples was composed of 6 phyla， 50 orders and 164 genera of fungi and 11 phyla， 43 orders and 123 genera of bacteria. The fungal taxa Ascomycota and Basidiomycota were the dominant phyla in each sample， with a total abundance of more than 90% in each sample. The abundance of the fungal genera Fusarium and Candida in silage maize with disease was higher than that in the CK treatment， and the abundance of Penicillium and Aspergillus in the YM and YX was higher than that in the CK treatment， while the abundance of Wickerhamomyces in silage maize with disease was lower than in the CK treatment. Firmicutes and Proteobacteria were the dominant bacterial phyla in each sample， with a total abundance of more than 99% in each case. The abundance of Enterococcus and Weissella was higher in the CK treatment than in the treatments with disease； and Streptococcus was only present in the CK treatment， with a relative abundance of 0.003%. In summary， this study has clarified the microbial community structure during maize silage fermentation in disease-free crop substrate and in crops affected by four different fungal diseases and identified the dominant bacterial genera present during fermentation in each case. Our study showed that the presence of fungal diseases resulted in an increase in the abundance of disease-causing pathogens， which decreased the abundance of Enterococcus， Weissella and Streptococcus. These changes would potentially have a negative impact on the silage fermentation environment， and affect the normal progress of the fermentation process， possibly leading to a decline in silage quality. Our results also provide information for the subsequent study of quality in maize silage.

Key words: silage corn, pathogenic fungi, microbial diversity, Illumina sequencing