AUTHOR=Zeng Xiangnan , Zhang Xin , Peng Bo , Xie Bingyue , Yuan Yuan , Yao Hui , You Xiangwei , Wei Jianyu , Li Yiqiang 

TITLE=Chitooligosaccharide enhanced the efficacy of Bacillus amyloliquefaciens CAS02 for the control of tobacco black shank

JOURNAL=Frontiers in Microbiology

VOLUME=14

YEAR=2023

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2023.1296916

DOI=10.3389/fmicb.2023.1296916

ISSN=1664-302X

ABSTRACT=<sec><title>Introduction</title><p>Tobacco black shank is a devastating soil-borne disease caused by the oomycete <italic>Phytophthora nicotianae</italic>, severely hamper tobacco production worldwide. However, the synergistic effect of biocontrol bacteria and marine polysaccharides/oligosaccharides on tobacco black shank control was few documented.</p></sec><sec><title>Methods</title><p>In this study, <italic>Bacillus amyloliquefaciens</italic> CAS02 (CAS02) and chitooligosaccharide (COS) were screened firstly, and their synergistic antagonistic effect against <italic>P. nicotianae</italic> and the underlying mechanism were investigated <italic>in vitro</italic> and <italic>in vivo</italic>.</p></sec><sec><title>Results</title><p><italic>In vitro</italic> experiments showed that, compared with the application of CAS02 or COS alone, co-application of CAS02 and COS significantly increased the inhibition rate against <italic>P. nicotianae</italic> by 11.67% and 63.31%, respectively. Furthermore, co-application of CAS02 and COS disrupted the structure of mycelia to a greater extent. The co-application of CAS02 and COS showed synergistic effect, with the relative control effect maintained above 60% during the 60-day pot experiment, significantly higher than that of application CAS02 or COS alone. The combined application of CAS02 and COS reduced the relative abundance of <italic>P. nicotianae</italic> in the rhizosphere soil and increased the relative abundance of bacterial taxa potentially involved in disease suppression, such as <italic>Nocardioides</italic>, <italic>Devosia</italic> and <italic>Bradyrhizobium</italic>. Meanwhile, CAS02 and COS synergistically activated salicylic acid (<italic>SA</italic>), ethylene (<italic>ET</italic>), and hypersensitive response (<italic>HR</italic>) defense signaling pathways in tobacco plants.</p></sec><sec><title>Discussion</title><p>Our findings demonstrate that co-application of CAS02 and COS remarkably improve the relative control effect against tobacco black shank through multiple pathways and provide a promising strategy for the efficient green control of tobacco black shank.</p></sec>