Impact of Soil Moisture Regimes on Wilt Disease in Tomatoes: Current Understanding

Abstract

Ralstonia solanacearum is a causal agent of vascular wilt disease in more than 200 crop species, including the tomato. R. solanacearum is a strict soil-borne pathogen and thrives in moist soils (Van der Wolf et al., 1998). The bacterium can live for years in an infected field, and has been reported to persist for 12 months in potato fields (van Elsas et al., 2000). The sources of inoculum for agricultural fields are irrigation and surface water, weeds, infested soil, latently infected propagative plant material, and contaminated farm tools and equipment. The bacteria exhibit subterranean movement and spread from the infected plants’ roots to the healthy ones (Hayward, 1991). R. solanacearum-caused wilt in tomato amounts to a 35%–90% yield loss under high temperatures and high moisture conditions (Singh et al., 2015). R. solanacearum colonizes the nutrient-poor xylem vessels, which are characterized by dead tracheary elements that have a relatively low osmotic pressure, which makes the pathogen penetration easy (Yadeta and Thomma, 2013). Vasse et al. (1995) observed that in tomatoes, the bacteria are attracted to the root wounds through an unknown mechanism, and stick to the epidermal cells’ surface.