Screening, Identification and Efficacy Evaluation of Antagonistic Bacteria for Biocontrol of Soft Rot Disease Caused by Dickeya zeae

Abstract

Dickeya zeae is the causal agent of bacterial soft rot disease, with a wide range of hosts all over the world. At present, chemical agents, especially agricultural antibiotics, are commonly used in the prevention and control of bacterial soft rot, causing the emergence of resistant pathogens and therefore increasing the difficulty of disease prevention and control. This study aims to provide a safer and more effective biocontrol method for soft rot disease caused by D. zeae. The spot-on-lawn assay was used to screen antagonistic bacteria, and three strains including SC3, SC11 and 3-10 revealed strong antagonistic effects and were identified as Pseudomonas fluorescens, P. parafulva and Bacillus velezensis, respectively, using multi-locus sequence analysis (MLSA) based on the sequences of 16S rRNA and other housekeeping genes. In vitro antimicrobial activity showed that two Pseudomonas strains SC3 and SC11 were only antagonistic to some pathogenic bacteria, while strain 3-10 had broad-spectrum antimicrobial activity on both pathogenic bacteria and fungi. Evaluation of control efficacy in greenhouse trials showed that they all restrained the occurrence and development of soft rot disease caused by D. zeae MS2 or EC1. Among them, strain SC3 had the most impressive biocontrol efficacy on alleviating the soft rot symptoms on both monocotyledonous and dicotyledonous hosts, and strain 3-10 additionally reduced the occurrence of banana wilt disease caused by Fusarium oxysporum f. sp. cubensis. This is the first report of P. fluorescens, P. parafulva and B. velezensis as potential bio-reagents on controlling soft rot disease caused by D. zeae.

Selection of Bacterial Strains for Control of Root-Knot Disease Caused by Meloidogyne incognita

“…Our own results and data of other researchers [ 29 , 47 , 48 , 49 , 64 , 67 , 74 , 75 , 76 , 77 ] demonstrated a strong antagonistic activity of B. velezensis to the pathogenic fungi Fusarium graminearum , F. oxysporum and R. solani, thus confirming this species as a very promising biocontrol agents [ 24 , 78 , 79 ]. Practical value of this antagonism has been proved by the use of B. velezensis in BioYield commercial formulation applied in management of soil-born pathogens and M. incognita on tomato [ 11 ].…”

Exploration of the Quorum-Quenching Mechanism in Pseudomonas nitroreducens W-7 and Its Potential to Attenuate the Virulence of Dickeya zeae EC1

“…The resulting sequence was compared to sequences in GenBank using a BLAST search through the National Center for Biotechnology Information (NCBI). In addition, multilocus sequence analysis (MLSA) by using housekeeping genes DNA gyrase subunit B ( gyrB ), RNA polymerase β subunit ( rpoB ), and RNA polymerase subunit D ( rpoD ) for Pseudomonas , and using primer pairs of GyrBPUN1F/GyrBPUN1R, LAPS5F/LAPS27R, and PsEG30F/PsEG790R, respectively, is required to clarify the classification status of the W-7 strain ( Li et al, 2020 ). All the resultant sequences were aligned and concatenated in the same order.…”

Identification of FadT as a Novel Quorum Quenching Enzyme for the Degradation of Diffusible Signal Factor in Cupriavidus pinatubonensis Strain HN-2

“…Three replicates of each treatment were used, and the experiments were carried out at least thrice. Daily records of symptoms were taken after bacterial inoculation [51,58]. The details of the tests are as follows: The strains used in this part were already cultured in 5 mL LB medium and shaken at 30 • C and 200 rpm for 12-16 h. Then, 100 µL of bacterial suspensions were inoculated on each plant.…”