Antifungal Activity against Fusarium oxysporum of Botanical End-Products: An Integration of Chemical Composition and Antifungal Activity Datasets to Identify Antifungal Bioactives

Plants produce various compounds as defensive barriers to naturally control fungal diseases. Among them, vascular wilt caused by Fusarium oxysporum is one of the most destructive diseases in crops, causing relevant economic losses. The application of synthetic fungicides is the most used management for this disease. However, this kind of method also involves adverse environmental impacts. Therefore, alternative methods are continuously being developed as a strategy to be involved in integrated pest management programs. Thus, as part of our research on antifungals of plant origin, a group of botanical extracts was assessed for the respective inhibitory effect on mycelium and conidia of F. oxysporum. Mycelial growth inhibition was measured in 12-well plates containing amended semi-solid medium, whereas conidial susceptibility was determined through microdilution. The identification of the bioactive compounds among test extracts was performed using an indirect approach, consisting of the integration of chemical composition and antifungal activity datasets through single-Y orthogonal partial least squares (OPLS) regression. Results showed that Piper aduncum extract was the most potent mycelial growth inhibitor whereas P. elongatum exhibited the best effect on conidia susceptibility. The active compounds identified through statistical integration and subsequent isolation were piperaduncin C, asebogenin and (−)-methyllinderatin. These findings indicated that the integrative, indirect approach is useful for the identification of bioactive metabolites from botanical extracts to be further used as biological protective agents against this phytopathogen.

Effect of Different Botanical Extracts and Organic Compound in The Management of Leaf Spot Disease of Strawberry (Fragaria ananassa Duch.) Caused by Pestalotia longisetula under Field Condition

A field experiment was carried out using sweet sensation variety of strawberry to check the efficacy of different botanical extracts and organic compounds to manage leaf spot disease. The study was done using ten treatments viz; ginger (T1), turmeric (T2), garlic (T3), ginger + turmeric + garlic (T4), cow urine (T5), cow urine+ ginger + turmeric + garlic (T6), compost tea (T7), compost tea+ ginger+ turmeric+ garlic (T8), SAAF (mancozeb 63 % + carbendazim 12%) (T9) and control (T10), which was replicated thrice. The parameter observed during experiment were plant height, leaf number, disease leaves, stem lesions, yield, percent disease incidence, disease severity percent and percent disease control. At 75 days of transplantation, the highest plant height, leaf number (24.60) and yield (1391.67 gm/plot) were observed in treatment compost tea (18.14 cm), cow urine+ ginger+ turmeric+ garlic and garlic respectively and lowest in treatment control (16.19 cm, 23.27 & 566.67 gm/plot). The disease leaves and stem lesions were observed highest in treatment control (3.40&3.23) and lowest in treatments garlic (3.0), and cow urine+ ginger+ turmeric+ garlic (1.83) respectively at 75 days after transplantation. Moreover, the highest percent disease incidence and disease severity percent were observed highest in treatments control (28.94% & 84.81%) and percent disease control in treatment garlic (42.36%) at 75 days of transplantation. Therefore, it is suggested to use garlic extracts as a measure to control leaf spot disease of strawberry. Int. J. Appl. Sci. Biotechnol. Vol 9(3): 193-202.

Effect of Botanical Extracts on Late Blight (Phytopthora infestans) and Productivity of Tomato (Solanum esculentum)

Late blight is caused by Phytopthora infestans (Mont.) de Bary which establishes quickly in Solanum esculentum L. (tomato); as a result, it makes the pathogen one of the most devastating plant diseases across the world. The control of late blight is difficult because P. infestans has advanced and complex enzymes and effecter molecules coded by avirulence genes. As such, a study was carried out at the University of Zimbabwe, Department of Plant Production Sciences and Technologies, between August 2018 and May 2019 to evaluate the efficacy of Moringa oleifera Lour. (moringa), Eucalyptus nigra R.T. Baker (gumtree), and Lantana camara L. (sensu lato) (lantana) extracts as biofungicides on late blight development on S. esculentum. The effect of acetone, ethyl acetate, and water extracts of M. oleifera, E. nigra, and L. camara on percent inhibition and radial growth were evaluated in the laboratory. In addition, the efficacy of different extract concentrations of M. oleifera, E. nigra, and L. camara L. on defence enzymes, disease incidence, disease severity, and yield parameters of S. esculentum were assessed in the in vivo experiment. Increasing concentration of the botanical extracts significantly ( p ≤ 0.05 ) reduced radial growth and increased percent inhibition of P. infestans. In addition, increasing botanical extract concentration significantly ( p ≤ 0.05 ) increased peroxidase (PОD), phenylalanine ammonia lyse (PAL), and polyphenol oxidase (PPO) activity. Disease incidence and severity were significantly ( p ≤ 0.05 ) reduced as the concentration of the botanical extracts increased. Similarly, marketable and total yield significantly ( p ≤ 0.05 ) increased with increase in the botanical extract concentration. Gas chromatography mass spectrometry (GCMS) revealed the presence of furfural, 5-methyl-4- (trifluoromethyl) pyrido, dodecanamide, cyclopentasiloxane, and decamethyl. From the research, it can be concluded that M. oleifera ethyl acetate, E. nigra ethyl acetate, and L. camara water extracts contain antifungal compounds and can be used as biofungicides in late blight management.