Influence of Seedling Age on the Susceptibility of Tomato Plants to <i>Ralstonia solanacearum</i> during Protray Screening and at Transplanting

Abstract

The study was undertaken to assess whether seedling age played any role in governing the vulnerability of tomato to the bacterial wilt pathogen, Ralstonia solanacearum, based on the preliminary observations that the extent of mortality during seedling-stage screening was relatively less in older seedlings. Employing the virulent strain 'NH-Av01' isolated from tomato, 2-, 3-, 4-or 5-weekold seedlings of susceptible 'Arka Vikas' raised in organic cocopeat in 98 cavity protrays were inoculated with the pathogen through root-injury inoculation approach. Disease symptoms appeared earlier and with more severity in 2-week-old seedlings followed by 3-, 4-and 5-week-old saplings recording 74%, 68%, 63% and 49% mortality, respectively, after four weeks of inoculation suggesting that older the seedlings, less the susceptibility to the pathogen. The growth characteristics of seedlings (shoot height, shoot and root weights) showed a significant increase with seedling age (0.21, 0.54, 1.14 and 2.09 g gross weight/seedling at 2, 3, 4 and 5 weeks, respectively) indicating healthier saplings with delay in inoculation time. In subsequent trials, seedlings of 3, 4, 5 or 6 weeks were transplanted to field-sick soil in protrays or in pots with monitoring for 1 -4 months which indicated a significant reduction in disease incidence and severity with increase in seedling age. The observations suggested that seedling age should be considered as a major factor influencing the susceptibility of tomato seedlings to R. solanacearum with the chances of variations in the extent of disease incidence or inconsistent results during seedling-stage screening and the possibility of escapes with older seedlings. Two-week seedlings formed the best when the aim is to induce maximum disease incidence, while transplanting at 5 -6 weeks stage appeared the best when the objective is minimal disease incidence or formulating disease management strategies.

Direct Delivery of Inoculum to Shoot Tissue Interferes with Genotypic Resistance to Ralstonia solanacearum in Tomato Seedlings

“…The virulence of pathogen or the susceptibility of the genotype is known to be altered with higher temperatures. Our recent observations suggest that seedling age is also a crucial factor in governing the susceptibility of tomato to Ralstonia with older seedlings proving less vulnerable and 2‐week stage emerging as the best towards screening purpose (Thomas and Upreti ). Under our given conditions, the most appropriate method for seedling‐stage screening emerged to be root‐injury inoculation at 2 weeks.…”

Ralstonia solanacearum virulence in tomato seedlings inoculated by leaf clipping

“…It is important to note that there is a recent report that showed infection of tomato seedlings by R. solanacearum (Thomas & Upreti, ). However, unlike this previous study, the present method has avoided contact of the tomato seeds with the soil, starting from seed germination to infection assay completion.…”

In Vitro Evaluation of Antibacterial Chemicals and Bioagents against Ralstonia solanacearum Infecting Bacterial Wilt in Ginger

“…The inoculated plant lost turgidity; leaves started dropping and plant wilted suddenly (Fig.4). Pathogenicity of R. solanacearum causing bacterial wilt was proved earlier by several workers (Winstead and Kelman, 1952;Schell M. A., 2000;Williamson et al, 2002;Rajan et al, 2002;Kumar and Sarma, 2004;Umesha et al, 2005;Hikichi, 2007;Rashmi et al, 2012;Artal, 2012;Thomas and Upreti, 2014;Zulperi et al, 2014). Kumar A.…”