Archivio Journal of Plant Pathology

Abstract:

Bacterial wilt of sweet pepper, caused by Ralstonia solanacearum (Rs) race 1, is a limiting disease in northern and northeastern Brazil. The present study evaluated the effect of silicon (Si) on the disease in the sweet pepper cv. Enterprise, which was grown in a substrate containing 0.00, 0.25, 0.50, 1.50, or 3.00 g SiO2 kg-1and was subsequently transplanted into soil infested with Rs CGM-8. The following variables were evaluated: latency period (LP50); incidence; bacterial wilt index (BWI); area under the disease progress curve (AUDPC); biomass; accumulation of Ca+2, Mg+2, and Si; total protein and enzymatic activity; chemical characteristics of the substrate; and in vitro bacterial growth. A dose of 2.95 g Si kg-1substrate increased the LP50 (33.6%) and reduced the BWI (98%) and AUDPC (93.7%); this treatment also increased Ca+2 levels in the shoots and reduced Mg+2levels in the shoots and the roots. Supplementation with various doses of Si yielded maximum increases in the shoot fresh biomass (121.8%), the root fresh biomass (83.6%), and the shoot dry biomass (84.9%); increased the concentrations of total protein, catalase, ascorbate peroxidase, and chitinase; caused the accumulation of Si in the shoots and substrate; increased the pH, Na+, and K+; and decreased P in the substrate. The putative mechanisms of action of Si included a direct effect on colonization of the pathogen, an indirect effect on the plant’s development, increased Ca+2 absorption, and signaled for the production of plant defence enzymes. Therefore, the production of sweet pepper seedlings in a substrate containing calcium silicate (2.95 g SiO2 kg-1) could be utilized as an alternative cultivation practice for the management of bacterial wilt disease. More research is needed to elucidate the exact mechanisms of silicon and its effects on latent infections and on bacterial cells and population.