Ralstonia solanacearum virulence in eggplant seedlings by the leaf-clip inoculation

Abstract

Ralstonia solanacearum causes a lethal bacterial wilt disease in numerous plants including important vegetable crops such as eggplant and tomato. One of the difficulties in studying virulence of this bacterium in different host plants is the development of an easy and stable pathogenicity assay. Recently we described a leaf-clip inoculation method to study its pathogenicity at the cotyledon stage of tomato seedlings. Hereafter, we demonstrated the leafclip inoculation method to be equally efficient for studying R. solanacearum pathogenicity in the cotyledon stage of eggplant seedlings. Our study revealed eggplant seedlings to be highly susceptible to R. solanacearum as compared to tomato seedlings, illustrated by appearance of disease symptoms in significantly higher number of seedlings. We also tested the virulence of several global transcription regulator mutants of R. solanacearum including hrpB, hrpG and phcA in eggplant seedlings. The phcA mutant was found to be only moderately virulence deficient in eggplant seedlings but was significantly reduced in virulence in tomato. This is indicative of some host specific responses towards certain pathogenicity functions of R. solanacearum, which are markedly different in tomato and eggplant seedlings. Apart from being economical in requiring less labor, time and space, this simple gnotobiotic leaf-clip inoculation method is anticipated to be helpful in further exploring the interaction between R. solanacearum and eggplant seedlings at the cotyledon stage.

Ralstonia solanacearum Virulence in Cotyledon Stage Tomato Seedlings

“…First, in both leaf [12] and root inoculation [14] studies, the seedlings are kept in sterile water which ensures minimal interaction with other micro-organisms. This has facilitated to study R. solanacearum infection under gnotobiotic condition [12][13][14]18]. It is evident that R. solanacearum infects and cause disease in seedlings without addition of some other bacteria from external sources such as soil.…”

“…The use of seedlings allows scoring the disease in a more accurate form as a large number of seedlings can be recruited for virulence study. The seedlings of tomato and eggplant can be inoculated by the pathogen either in the leaf [12,13] or in the root [14] to study its pathogenicity. The disease phenotype in seedling is observed within three days after inoculation.…”

Spread of bacterial wilt disease of potato in the highlands of Fouta Djalon, Republic of Guinea

“…Bacterial wilt, which is caused by the R. solanacearum species complex (RSSC), is one of the most devastating important and widespread bacterial diseases of vegetables in tropical environments (Buyela et al, 2017;Traoré et al, 2020). R. solanacearum is soil borne and affects a broad range of more than 450 species in 54 botanical families including monocots (Musaceae) and dicots (Solanaceae Potato, Pepper, Tomato, eggplant) in tropical, subtropical and warm temperature regions of the world (Phukan et al, 2019). The RSSC is composed of four evolutionary lineages, called phylotypes, whose origins have been inferred to Asia and Eastern Africa (phylotype I), America (phylotype II), Africa (phylotype III) and Indonesia (phylotype IV) (Fegan and Prior 2002; Wicker et al, 2012).…”

A study on twitching motility dynamics in Ralstonia solanacearum microcolonies by live imaging

“…Ralstonia solanacearum is a gram-negative, βproteobacterium, that causes a lethal wilt disease in many host plants [8][9][10]. The bacterium is a soil-borne, systemic phytopathogen but is also known to infect several hosts without causing disease [9,11].…”

“…Ralstonia solanacearum is a gram-negative, βproteobacterium, that causes a lethal wilt disease in many host plants [8][9][10]. The bacterium is a soil-borne, systemic phytopathogen but is also known to infect several hosts without causing disease [9,11]. It is a species complex armed with a wide array of virulence determinants that allow it to infect over 200 crop species belonging to 53 families [11].…”