Phytochemicals in Mondia whitei Confer Fungistatic Activity Against Alternaria solani and Phytophthora infestans and Improves Tomato (Solanum lycopersicum) Performance.

Abstract

Tomato is a significant vegetable, but is adversely attacked by several fungal diseases that lower yield. Bio-extracts from plants, as fungicides are safe to human and the environment. This study assessed the impact of Mondia whitei extracts on tomato plant growth and antifungal activity in vitro and in vivo and screened for fungistatic phytochemicals in the plant’s extract. The extracts were obtained from M. whitei roots using methanol, dichloromethane, and ethyl acetate solvents and tested against Alternaria solani and Phytophthora infestans at concentrations of 10% and 20% in vitro and 2.5%, 10%, and 20% in vivo. Ridomil was used as positive control and blank as negative control. In vitro and in vivo experiments were replicated three and four times, respectively, in a completely randomized design. The extracts completely inhibited in vitro growth of the pathogens. In vivo M. whitei-treated plants showed a significant reduction (p≤0.05) in A. solani and P. infestans disease incidences which were recorded at 18.57% and 35% respectively for 20% bio-extract. Tomato plants treated with negative control recorded 57.86% and 80% for A. solani and P. infestans, respectively. Disease severity index in A. solani inoculated plants was 4.43 for 20% bio-extract compared to negative control that recorded an index of 8.29. For P. infestans, 20% bio-extract recoded disease severity index of 7.14 compared to 10.42 in the negative control plants. Plant height increased with increase in extract concentration. Negative control, 2.5%, 10% and 20% bio-extract concentrations recorded heights of 93.49 cm, 119.04 cm, 128.72 cm and 133.96 cm respectively for A. solani inoculated plants and 99.30 cm, 99.97 cm, 111.42 cm and 117.71 cm respectively for P. infestans inoculated plants. Phytochemicals such as flavonoids, tannins, and steroids among others were detected. This study presents M. whitei as a potentially safe and affordable alternative to synthetic fungicides against fungal diseases in tomato crops.