Morphological, symptomatological and molecular characterization of Enterobacter cloacae causing bacterial wilt in African marigold (Tagetes erecta L.)

Abstract

Causal agent for bacterial wilt is reported to be Ralstonia solanacearum. Bacteria isolated from the wilted plants and cultured on TTZ medium, had white, highly fluidic and circular colonies with entire, slightly raised-margins and dark pink centre, compared to flat-margins and light pink centre in R. solanacearum. Artificial inoculation of the marigold seedlings in mist chamber with the fresh bacterial suspension at 0.3 OD resulted necrosis at leaf tip followed by slow wilting of plants whereas the entire plant wilts quickly in Ralstonia infection. Bacterial cells under SEM were larger in size with 0.5-0.9 × 1.2-1.92 µm compared to 0.3-0.5 × 1.2-1.7 µm reported in Ralstonia. PCR amplification and barcode analysis of the 16S rDNA region has yield 92 barcodes within 1273 bp, distinguishing the genera and phylogenetic analysis has placed our isolates among the E. cloacae accessions. This is the first report to prove that wilt in marigold is caused by E. cloacae.

Analysis of changes in bacterial diversity in healthy and bacterial wilt mulberry samples using metagenomic sequencing and culture-dependent approaches

“…Plant bacterial wilt is generally considered a highly destructive xylem disease caused by the R. solanacearum complex (RSSC). However, the advancement of bacterial wilt research shows that, in addition to other pathogens, the E. cloacae complex (ECC) can also cause bacterial wilt in African marigoldx ( Jeevan et al., 2022 ), ginger ( Cosmas et al., 2016 ) and mulberry plants ( Wang et al., 2008 ; Zhu et al., 2011 ). Although the pathogenic bacteria of mulberry bacterial wilt are said to be complex and diverse, they mainly include Ralstonia ( Pan et al., 2013 ), Enterobacter ( Wang et al., 2008 ; Wang et al., 2010 ; Zhu et al., 2010 ; Zhu et al., 2011 ; Zhou et al., 2021 ), Klebsiella ( Luo et al., 2022 ) and Pantoea ( Yuan et al., 2023a ).…”