Antibacterial potency of Pelargonium zonale and Psidium guajava against bacterial wilt of potato under greenhouse condition

Abstract

Pelargonium zonale and Psidium guajava plant extracts have demonstrated in-vitro antibacterial activity against Ralstonia pseudosolanacearum sp. nov. Nevertheless, their antibacterial effectiveness against this disease has not been examined under greenhouse condition. This study explored the antibacterial efficacy of ethanolic leave extracts of P. zonale and P. guajava in management of R. pseudosolanacearum sp. nov. of potatoes under greenhouse condition. The experiment was set in a completely randomized design (CRD) of 2*6 factorial arrangements [2 varieties (Shangi (Highly susceptible) and Sherekea (Moderately resistant) and 6 treatments] with 3 replicates. The treatments comprised; 2 ethanolic leave extracts (P. guajava and P. zonale) at 50 mg/mL, 2 positive controls [ENRICH BM (Bronopol 27%w/w) and KOBE 1.2 SL (Chrysophanol 12g/l)] at commercial rates and 2 negative controls (Untreated control and 1% DMSO). The soil media was inoculated with 10 mL of bacterial suspension adjusted to 600 nm OD (approximately 107 to 108 cfu/mL) per pot. Data was collected on disease incidence, disease severity, plant heights, number of stems, yield (Kgs) and number of bacterial wilt colony counts. The study results revealed that all the treated plants exhibited significantly low disease incidences, low area under disease progress curves (AUDPCs), high number of stems, high stem heights, low bacterial wilt colony counts and high yield (Kgs) compared to negative controls. Potato variety Sherekea exhibited the highest average efficacy from the two plant extracts; 0.14 for disease incidence, 1178.21 for AUDPC, 1.84 for stem height, 2.66 for bacterial wilt colony counts and 0.28 for yield (Kgs) respectively. These results demonstrated the synergistic effect of host plant resistance and/or tolerance and botanicals in management of R. pseudosolanacearum sp. nov. Further research is required to determine the effectiveness and stability of the two extracts against the target pathogen the field to enhance their adoption and commercialization in the management of bacterial wilt pathogen in infested potato production fields.