AUTHOR=Zhang Jingxin , Sun Dayuan , Shen Huifang , Pu Xiaoming , Liu Pingping , Lin Birun , Yang Qiyun 

TITLE=Dickeya fangzhongdai was prevalent and caused taro soft rot when coexisting with the Pectobacterium complex, with a preference for Araceae plants

JOURNAL=Frontiers in Microbiology

VOLUME=15

YEAR=2024

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2024.1431047

DOI=10.3389/fmicb.2024.1431047

ISSN=1664-302X

ABSTRACT=<p>Bacterial soft rot caused by coinfection with <italic>Dickeya</italic> spp. and <italic>Pectobacterium</italic> spp. in hosts can cause successive changes in fields, and it is difficult to prevent the spread of and control the infection. <italic>Pectobacterium</italic> spp. are prevalent in the growing areas of tuberous crops, including taro and potato. Recently, <italic>Dickeya fangzhongdai</italic> has emerged as a virulent pathogen in taro. To determine the prevalence status of the causal agents and evaluate the potential spreading risks of <italic>D. fangzhongdai</italic>, screening and taxonomic classification were performed on phytopathogenic bacteria collected from different taro-growing areas in Guangdong Province, China, and biological and genomic characteristics were further compared among typical strains from all defined species. The causative agents were verified to be phytobacterial strains of <italic>D. fangzhongdai, Pectobacterium aroidearum</italic> and <italic>Pectobacterium colocasium</italic>. <italic>P. aroidearum</italic> and <italic>P. colocasium</italic> were found to form a complex preferring Araceae plants and show intensive genomic differentiation, indicating their ancestor had adapted to taro a long time prior. Compared with <italic>Pectobacterium</italic> spp., <italic>D. fangzhongdai</italic> was more virulent to taro corms under conditions of exogenous infection and more adaptable at elevated temperatures. <italic>D. fangzhongdai</italic> strains isolated from taro possessed genomic components of additional T4SSs, which were accompanied by additional copies of the <italic>hcp</italic>-<italic>vgrG</italic> genes of the T6SS, and these contributed to the expansion of their genomes. More gene clusters encoding secondary metabolites were found within the <italic>D</italic>. <italic>fangzhongdai</italic> strains than within the <italic>Pectobacterium</italic> complex; interestingly, distinct gene clusters encoding zeamine and arylpolyene were both most similar to those in <italic>D</italic>. <italic>solani</italic> that caused potato soft rot. These comparisons provided genomic evidences for that the newly emerging pathogen was potentially equipped to compete with other pathogens. Diagnostic qPCR verified that <italic>D</italic>. <italic>fangzhongdai</italic> was prevalent in most of the taro-growing areas and coexisted with the <italic>Pectobacterium</italic> complex, while the plants enriching <italic>D</italic>. <italic>fangzhongdai</italic> were frequently symptomatic at developing corms and adjacent pseudostems and caused severe symptoms. Thus, the emerging need for intensive monitoring on <italic>D. fangzhongdai</italic> to prevent it from spreading to other taro-growing areas and to other tuberous crops like potato; the adjustment of control strategies based on different pathopoiesis characteristics is recommended.</p>