EFFECTS OF SOME PLANT EXTRACTS AGAINST Pythium myriotylum CAUSAL AGENT OF POST EMERGENCE DAMPING-OFF DISEASE IN Amaranthus

Abstract

The use of plant botanicals have gained a lot of attention in recent times, owing to the health and economic implications associated with their uses. Amaranthus hybridus has numerous nutritional values but it is affected largely by post emergence damping off disease. This research investigated the efficacy of the leaf extracts of three plant Neem (Azadirachta indica), Mango (Mangifera indica) and Mahogany (Khaya senegalensis) against Pythium myriotylum the causative pathogen of post emergence damping off disease in Amaranthus hybridus. The plant samples were collected, dried and extraction was done using the soxhlet apparatus. Qualitative and quantitative phytochemical screening was done using standard procedures. The causative pathogen (Pythium myriotylum) was isolated from infected A. hybridus leaves and the rhizosphere on PDA medium. Agar well diffusion technique was used to test for antagonism using three extract concentrations at 500, 800 and 1000 mg/mL. The control was without extract and three replicates of each were made. Incubation was done at 28±2 oC for 7 days. The radial growth of P. myriotylum at day 7 from Mahogany extract at 500, 800 and 1000 mg/ml concentrations were 4.00, 3.99 and 3.99 cm respectively, while values for Neem extracts were 3.98, 3.86 and 3.55cm and Mango extract were 4.00, 3.12 and 2.75 cm. The results obtained showed that the plant extracts have positive potentials towards inhibiting the pathogen (P. myriotylum) with Mango extract having the highest inhibition potential followed by Neem extract and Mahogany extract recorded the lowest. The percentage inhibition at 500, 800 and 1000 mg/mL from Mahogany extract across the concentrations were 0.00, 0.25 and 0.25 % respectively. While Neem were 0.5, 3.5 and 11.25 % and the percentage inhibition from Mango extract were 0.00, 22.00 and 31.25 %. The study shows that mango extract had the highest inhibitory potential against the pathogen with 31.25 % at 1000 mg/ml concentration, while Neem extract followed with 11.25 % and Mahogany extract had the lowest inhibition with 0.25 % at 1000mg/ml. The results obtained from the invivo study showed that A hybridus seedlings that were infected with the pathogen developed resistance to the pathogen across all concentration gradients of the plant extracts except from Mahogany which could only suppress the disease at the highest concentration of 1000 mg/ml. Therefore, this study supports the use of these botanicals in the control of plant damping off disease of A. hybridus as it has proven to be effective.