Investigating Plant Extract in Inhibition of Ralstonia solanacearum Responsible for Potato Wilt

Controlling the Potato Bacterial wilt disease caused by Ralstonia solanacearum remains a significant challenge for Kivu’s producers in Democratic Republic of Congo, especially due to limited access to healthy planting material. Therefore, this study aimed to identify effective plant species within the traditional medicine in Kivu whose extracts have the potential to inhibit the bacterium. Eighteen plant extracts were tested using the Mueller Hinton Agar diffusion method. The extract was obtained by grinding 65 grams of dry plant powder macerating in 250 ml of methanol and drying. Then 40 mg of extract was mixed with 10 µl of DiMethyl SulfOxide (DMSO) and 50 µl of sterile distilled water (SDW). The bacterium was isolated from necrotic potato vascular tissue exhibiting wilt symptoms. 500 µl of 1 cm2 sterilized tissue ground in 9 ml SDW was inoculated on MacConkey agar and incubated at 28 °C. After 48 hours, biochemical tests and the disease sensitivity were tested by inoculating healthy potato plants. Results showed that Eucalyptus globulus emerged as the statistically most effective species, exhibiting a notable inhibition area of 19.33 mm in diameter. This was followed closely by Capsicum frutescens, Manihot glasiovii, Datura stramonium, Pteridium aquilinum, Galinsoga parviflora, Tithonia diversifolia, and Cupressus sempervirens, each showing an inhibition zone of 17.33 mm. From this list, the five most effective extracts revealed an abundance of phenols after phytochemical screening. Based on these results, it would be interesting to evaluate the effectiveness of the extracts in disinfecting garden tools and to assess the role of phenol in inhibiting the bacterial growth.