New report of additional enterobacterial species causing wilt in West Bengal, India

Abstract

Ralstonia solanacearum is known to be the most prominent causal agent of bacterial wilt worldwide. It has a wide host range comprising solanaceous and nonsolanaceous plants. Typical symptoms of the disease are leaf wilt, browning of vascular tissues, and collapsing of the plant. With the objective of studying the diversity of pathogens causing bacterial wilt in West Bengal, we collected samples of diseased symptomatic crops and adjacent symptomatic and asymptomatic weeds from widespread locations in West Bengal. By means of a routine molecular identification test specific to "R. solanacearum species complex", the majority of these strains (68 out of 71) were found to not be R. solanacearum. Presumptive identification of these isolates with conventional biochemicals, extensive testing of pathogenicity of a subset involving greenhouse trials fulfilling Koch's postulate test, and scanning electron microscopic analysis for the presence of pathogen in diseased plants were done. 16S rDNA sequencing of a subset of these strains (GenBank accession Nos. JX880249-JX880251) and analysis of sequences with the nBLAST programme showed a high similarity (97%-99%) to sequences of the Enterobacteriaceae group available in GenBank. Molecular phylogeny further established the taxonomic position of the strains. The 3 bacterial strain cultures have been submitted to MTCC, Institute of Microbial Technology, Chandigarh, India, and were identified as Klebsiella oxytoca, Enterobacter cowanii, and Klebsiella oxytoca, respectively. Although Enterobacter sp. has previously been reported to cause wilt in many plants, susceptibility of most of the dedicated hosts of R. solanacearum to wilt caused by Enterobacter and other bacteria from Enterobacteriaceae is being reported for the first time in this work.

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

“…The bacteria observed under the scanning electron microscope were rod shaped with 0.5-0.9 × 1.2-1.92 µm size. The bacterial cells were larger compared to the sizes reported for Ralstonia solanacearum (Anjali 2019;Sarkar and Chaudhuri 2015).…”

“…Bacterial wilt causes huge losses in many crops (Thakur et al 2014;Mathew 2020) and R. solanacearum has been considered as the causal agent until it was reported that the wilt in tomato is caused by E. cloacae (Sarkar and Chaudhuri 2015). Based on the nearly similar wilting symptoms and previous reports (Álvarez et al 2010), pathogen causing the wilt in marigold was thought to be R. solanacearum (Umesh et al 2018).…”

“…E. cloacae and related species complex are pathogenic in Macadamia nut, mulberry, lucerne, cassava, tomato, ginger and hot pepper in Hawaii, Malaysia, China, Venezuela, Mexico, Malaysia and India, respectively (Sarkar and Chaudhuri 2015;García-González et al 2018;Liu et al 2020). Moreover, this bacterium has been reported to cause internal yellowing in papaya and internal decay in onion and Odontioda orchids and stunting and death in rice (Cao et al 2020).…”

Interaction between Meloidogyne javanica and Ralstonia solanacearum in Chili

“…irrigation water, budding, grafting, ornamental tubers, potatoes, vegetables and banana (Flores-Cruz and Allen, 2009) but the most damaging source of dispersal is waterways (Elphinstone, 2005). The bacterium enters through natural openings and moves towards the xylem vessels where it blocks the supply of minerals and water and causes vascular browning, yellowing and stunting in many plants (Smith, 1920;Sarkar and Chaudhuri, 2015). Other symptoms include narrow dark strips beneath the epidermis, growth of adventitious roots on the stem, epinasty beneath the leaves, and oozing of bacteria in the form of slimy material when the infected stem is cut (Sarkar and Chaudhuri, 2015).…”

“…The bacterium enters through natural openings and moves towards the xylem vessels where it blocks the supply of minerals and water and causes vascular browning, yellowing and stunting in many plants (Smith, 1920;Sarkar and Chaudhuri, 2015). Other symptoms include narrow dark strips beneath the epidermis, growth of adventitious roots on the stem, epinasty beneath the leaves, and oozing of bacteria in the form of slimy material when the infected stem is cut (Sarkar and Chaudhuri, 2015). The bacterium causes bacterial wilt which is a destructive disease of many plants and has caused significant yield losses in solanaceous crops worldwide (Yabuuchi et al, 1995;Hayward et al, 2005).…”