Abstract:

Allium fistulosum is one of the main characteristic economic crops in Tongxin, Ningxia, but the occurrence of soft rot disease affected the yield and quality of A. fistulosum. The analysis of the composition and diversity of endophytic bacterial communities related to the soft rot of A. fistulosum aims to provide a theoretical basis for understanding the mechanism of soft rot disease occurrence and determining the pathogenic bacteria. 16S rDNA high-throughput sequencing technology and traditional isolation methods were used to compare the commonalities and differences of endophytic bacterial communities in healthy and soft rot plants of A. fistulosum. A total of 1334 OTUs were obtained from healthy and diseased samples, and the richness and diversity of endophytic bacteria were lower in diseased samples than in healthy samples. There were significant differences in endophytic bacterial communities between the two samples, with Proteobacteria as the dominant phylum, and its relative abundance in diseased and healthy plants was 82.51% and 43.49%, respectively. At the genus level, unclassified Enterobacteriaceae was the dominant genus in diseased samples (46.59%), while Chryseobacterium (11.98%), Pseudomonas (7.10%), and Flavobacterium (5.01%) were dominant genera in healthy samples. The bacterial strains isolated from healthy and diseased samples belonged to 11 genera, including 4 genera endemic to healthy plants, 2 genera endemic to diseased plants, and 5 genera owned by both. Among them, Bacillus and Microbacterium were endemic genera to healthy plants with high isolation frequency, which may be related to disease resistance of healthy A. fistulosum; Klebsiella and Pseudomonas were common genera, and had a high isolation frequency in diseased plants. This study confirmed that the changes of endophytic bacterial diversity and community composition in A. fistulosum were closely related to the occurrence of soft rot disease, but the identification of pathogenic bacteria still requires screening and detection using multiple methods.

Key words: Allium fistulosum, soft rot disease, endophytic bacteria, 16S rDNA, high-throughput sequencing