Dynamics of microbial community composition on grass surfaces in response to glucose and sucrose spraying for enhanced silage quality

This study was to investigate the effects of glucose and sucrose spraying on the microbial community on the surface of Italian ryegrass ( Lolium multiflorum ) and alfalfa ( Medicago sativa ) ，and thereby provide a theoretical foundation for the preparation of high-quality silage. To assess the changes in microbial profile, 16S rRNA amplicon sequencing technology was employed. Results showed that a total of eighty-oneoperational taxonomic units (OTUs), encompassing four phyla, eight classes, fifteen orders, twenty-one families, and thirty-one genera, colonized the surface of Italian ryegrass and alfalfa. At the phylum level, both plant materials were abundant in Proteobacteria (Italian ryegrass 87.73% and alfalfa 95.28%) and Bacteroidetes (Itlian ryegrass 10.22% and alfalfa 2.23%). At the genus level, Italian ryegrass was enriched with Methylobacterium (22.83%), Pseudomonas (16.32%), Rhizobium (13.12%), and Sphingomonas (12.63%), whereas alfalfa mainly included Pseudomonas (23.14%), Brucella (17.24%), and Methylobacterium (15.10%). Sucrose spraying enriched Sphingomonas and Xanthomonas in Italian ryegrass, while glucose spraying increased the abundance of Rhizobium and Pedobacter in Italian ryegrass. In alfalfa, Duganella and Erwinia were enriched by sucrose spraying. Overall, glucose and sucrose spraying led to change microorganism alpha diversity and a significant LefSe difference. Furthermore, statistical variations in microorganisms were observed within seven days after spraying sucrose and glucose, and the changes varied across the grasses. Significance and Impact of Study: Microorganisms are very important for silage fermentation. This study reported the effects of spraying different sugars on the quantity and distribution of microorganisms on grass surface.