The Effect of Nitrogen Application Rates on the Structure and Diversity of Bacterial Communities in Cigar Tobacco Leaves at Different Periods

To clarify the effects of nitrogen application rates on the structure and diversity of bacterial communities in Fujian cigar tobacco leaves at different periods, this study used Haiyan 204 as the test material. Utilizing Illumina high-throughput sequencing technology, we analyzed the results of bacterial community structure, diversity and predicted functions in leaves subjected to different nitrogen treatments (N0, no nitrogen application; N1-N4, 120, 180, 210, 240 kg/hm² of nitrogen). Analyses were conducted at three key stages: field maturity, and the browning and stem-dry stages during air-curing. The results showed that Proteobacteria and Actinobacteria were the dominant phyla, while Sphingomonas, Methylobacterium, Aureimonas and Pseudomonas were the dominant genera across all periods and treatments. The nitrogen application significantly affected the abundance of Sphingomonas and Pseudomonas during the browning and stem-dry stage of air-curing. Nitrogen application had a small effect on bacterial α diversity, but significantly affected bacterial β diversity in the browning and stem-dry stage in the air-curing periods. In the mature and browning stage, the bacterial community was mainly associated with carbohydrate metabolism, amino acid metabolism, membrane transport, energy metabolism and other functions, while in the stem-dry stage, it was mainly associated with cell growth and death, and cellular motility and other functions.