Sampling period and disease severity of bacterial wilt significantly affected the bacterial community structure and functional prediction in the sesame rhizosphere soil

Abstract

The changes in the structure and function of bacterial communities present in the rhizosphere soils are of great significance for disease control in sesame, but it remains unclear to date. The present study explored the effects of five sampling periods (F0, day 0 after the first flowering; F11; F21; F32; F48) and three disease severities (H0, healthy; D5, moderate diseased; D9, serious diseased) on the structure and function using high throughput sequencing. The results indicated that the values of the Obs, Shannon, Chao1, and ACE first increased and then decreased in the D5 and D9 groups as plants matured, while an increasing trend was observed in the H0 group. The relative abundances of Actinobacteria and Proteobacteria demonstrated a trend from lower values to increased values and then again to lower values in the later sampling period. In the D9 group, Ralstonia experienced a significant 2.15-fold increase during the F0 period, while Gemmatimonas and Streptomyces demonstrated significant increases of 0.65 and 0.30 percentage points, respectively, in the D9 group during the F11 and F21 periods compared to H0. The predominant phyla in the H0 group during the F0 and F11 periods were p_Verrucomicrobiota and p_Firmicutes, respectively. In the D5 group during the F11 period, there were notable increases in xenobiotics biodegradation and metabolism (7.72%) and amino acid metabolism (0.80%) compared to H0, while nucleotide metabolism, replication and repair, and translation experienced significant decreases of 1.85%, 2.16%, and 1.64%, respectively. This critical period preceding the final flowering influenced the structure and function of bacterial communities in the sesame rhizosphere soil. The available potassium and boron exhibited a significant negative correlation with the phyla Proteobacteria and Crenarchaeota, while these phyla were significantly positively correlated with the genera Sphingomonas, Ramlibacter, and Gemmatimonas in the rhizosphere soil, and Carbohydrate_Metabolism and Cell_Motivity of the bacterial functions. The findings contribute to the understanding of the temporal dynamics of microbial communities and their functions in sesame rhizosphere soil, and their response mechanisms to bacterial wilt severity.