Microbial bio-products are becoming an appealing and viable alternative to chemical pesticides for effective management of crop diseases. These bio-products are known to have potential to minimize agrochemical applications without losing crop yield and also restore soil fertility and productivity. In this study, the inhibitory efficacy of 2,4-diacetylphloroglucinol (DAPG) produced by Pseudomonas fluorescens VSMKU3054 against Ralstonia solanacearum was assessed. Biochemical and functional characterization study revealed that P. fluorescens produced hydrogen cyanide (HCN), siderophore, indole acetic acid (IAA) and hydrolytic enzymes such as amylase, protease, cellulase and chitinase, and had the ability to solubilize phosphate. The presence of the key antimicrobial encoding gene in the biosynthesis of 2,4-diacetylphloroglucinol (DAPG) was identified by PCR. The maximum growth and antimicrobial activity of P. fluorescens was observed in king’s B medium at pH 7, 37 °C and 36 h of growth. Glucose and tryptone were found to be the most suitable carbon and nitrogen sources, respectively. DAPG was separated by silica column chromatography and identified by various methods such as UV-Vis, FT-IR, GC-MS and NMR spectroscopy. When R. solanacearum cells were exposed to DAPG at 90 µg/mL, the cell viability was decreased, reactive oxygen species (ROS) were increased and chromosomal DNA was damaged. Application of P. fluorescens and DAPG significantly reduced the bacterial wilt incidence. In addition, P. fluorescens was also found effective in promoting the growth of tomato seedlings. It is concluded that the indigenous isolate P. fluorescens VSMKU3054 could be used as a suitable biocontrol agent against bacterial wilt disease of tomato.

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Aims: Senna alata (Carrion crow bush), Senna bicapsularis (Money bush) and Pityrogramma calomelanos (Wild maran) are known for their value in traditional medicine. The study was an effort to identify, environment friendly antifungal compounds from these locally available plants against fungal pathogen Curvularia lunata. Study Design: An experiment based study done to identify antifungal property and phytochemical identification of C. lunata. Place and Duration of Study: Plants were collected from the coastal areas of Guyana and identified at the Biodiversity Center, University of Guyana, Guyana between January 2017- May 2017. Methodology: Phytochemical extraction was conducted using soxhlet and rotovap apparatus. Hexane, methanol and aqueous extracts of plants were analyzed for antifungal properties. Antifungal activity was tested using the poisoned food and well diffusion technique. Data analysis of the study was done using R-Studio Program for statistical computing and graphics. A Tukey test was done along with ANOVA and Boxplots. Results: Methanol extract of P. calomelanos showed maximum antifungal activity with an inhibition percentage of 60.3% at 400 µl, with poison food technique. With well diffusion method, P. calomelanos showed an inhibition zone of 54 mm at 500 µl. Saponins, steroids and glycosides were identified with methanol extract of P. calomelanos. Conclusion: The finding of this study indicates, the possible use of P. calomelanos extract as an antifungal agent against C. lunata and its potential to control fungal plant diseases.

Aims: Medicinal plants have been a fundamental part of the human health since existence. Guyana is surrounded high in the green shoulder of northern South America and shares Amazon River and Amazon Forest. South American population use plant extracts obtained from traditional medicinal plants as treatment for many infectious diseases. The study aimed to estimate antifungal property and chemical composition of the three medicinal plants Cymbopogon citratus (lemongrass), Cajanus cajan (pigeon pea) and Plectranthus amboinicus (thick leaf thyme) leaves collected from the coastal areas of Guyana. Study Design:  Experiment based study. Place and Duration of Study: Plants were gathered along the East Coast of Guyana and identified at the Biodiversity Center, University of Guyana, Georgetown, Guyana between January 2017- May 2017. Methodology: Phytochemical extraction was conducted using the soxhlet and rotovap apparatus and an aqueous extraction method. Data analysis of the study was done using R-Studio Program for statistical computing and graphics. A Tukey test was done along with ANOVA and Boxplots. Results: Qualitative analysis of phytochemicals was carried out and the presence of terpenoids, steroids, glycoside, alkaloid, tannins and saponins were positive in some plants. Antifungal activity was tested using the poisoned food and well diffusion techniques. Conclusion: In conclusion, C. cajan showed significant zones of inhibition using a well diffusion technique whereas hexane extract showed significant inhibition with poisoned food technique.

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