In vivo antibacterial activity of extracts of Tithonia diversifolia against Ralstonia solanacearum in tomato

Abstract

Currently, losses in crop yields caused by Ralstonia solanacearum have led to the overuse of synthetic pesticides, which are toxic and non-biodegradable hence detrimental to the environment. This study, therefore, investigated the in vivo antibacterial activity of ethanolic and hexane extracts from Tithonia diversifolia against R. solanacearum in tomatoes. Extraction was performed using the maceration method followed by evaluation of the extraction yields. During the in vivo greenhouse experiments, the antibacterial activity of the hexane and ethanolic extracts against R. solanacearum was performed using the root inoculation method while pathogenicity of the R. solanacearum strains to the susceptible Rio Grande 7-day-old tomato seedlings was investigated using root inoculation method under gnotobiotic conditions. The highest extraction yield of 2.8 ± 0.22 % w/w was observed in the ethanolic extracts of T. diversifolia, based on a dry weight basis. In vivo greenhouse experiments revealed that ethanolic extracts of T. diversifolia gave a percentage disease severity of 24 ± 2.6 % in the leaves and 32 ± 3.1 % in the flowers as compared to metham sodium (positive control), which gave a disease severity of 16 ± 2.2 % (p ˂ 0.01). Based on these findings, utilization of T. diversifolia ethanolic extracts is hereby fronted as efficient, cheap, and potent biopesticides for the effective control of R. solanacearum in tomato plants.