Evaluation of Some Selected Mango Varieties for Fruit Powder Production In Ghana

Mango is an important fruit, which receives high patronage in Ghana. However, the highly seasonal and perishable nature of the crop, besides being a constraint to both farmers and processors, also deny consumers the opportunity to enjoy the fruit all year round. Use of the stable powder form of mango can serve to fill the gap during the mango off-season. This study evaluated the fruits of four major mango varieties (“Keitt”, “Kent”, “Palmer” and a local variety) grown in Ghana for their suitability for fruit powder production. The fresh fruit pulp and reconstituted freeze-dried powder of the varieties were analyzed for physicochemical characteristics. The study revealed that “Keitt”, “Kent” and “Palmer”, which are the exotic varieties, had significantly (p≤0.05) high pulp content of 68%, 66% and 63% respectively indicating potential for high fruit powder yield. Acceptable levels of total soluble solids, titratable acidity, ascorbic acid and beta-carotene contents were observed in the fresh fruit and the freeze-dried powders of the varieties. There was no significant (p≤0.05) difference in Yellowness Index between fresh fruit pulp of “Keitt”, “Kent” and “Palmer” and their respective reconstituted freeze-dried powders. These three mango varieties exhibited considerably good quality in terms of physical and chemical characteristics for processing and utilization as fruit powder. The production of high quality mango powder from these varieties could therefore serve as substitutes in the off-season and also reduce postharvest loss

Involvement of Carnosic Acid in the Phytotoxicity of Rosmarinus officinalis Leaves

Weeds are rapidly developing resistance to synthetic herbicides, and this can pose a threat to the ecosystem. Exploring allelopathic species as an alternative weed control measure can help minimize the ecological threat posed by herbicide-resistant weeds. In this study, we aimed to evaluate the contribution of some polyphenols to the allelopathy of rosemary (Rosmarinus officinalis L.). The phytotoxic effects of rosemary (leaves, roots, inflorescences, and stems) crude extracts were tested on lettuce (Lactuca sativa L.). Soils incorporated with dried rosemary leaves were also tested on test plants. Reversed-phase high-performance liquid chromatography (HPLC) analysis was used to determine the content of some polyphenols (caffeic, ferulic, gallic, rosmarinic, carnosic, and chlorogenic acids) in rosemary. The specific activity and total activity of crude extracts and individual compounds were evaluated using lettuce. The crude extract of rosemary leaves showed the highest growth inhibitory effect among the rosemary organs tested. Soil amended with rosemary leaf debris reduced the dry matter and seed emergence of lettuce. Carnosic acid was the main compound detected in rosemary leaves and had a high specific activity when tested on lettuce. During the seed germination period, there was observed filter paper coloration among the test plants treated with carnosic acid (250 μg/mL). The high concentration and strong inhibitory effect of carnosic acid could explain the inhibitory activity of the rosemary leaf extract. Hence, we conclude based on the total activity estimation that carnosic acid among the other tested compounds is the major allelochemical in rosemary leaves

Efficacy of Beauveria bassiana against adults of Prostephanus truncatus (Horn), Sitophilus zeamais Motschulsky and Teretrius nigrescens Lewis in stored maize

The larger grain borer, Prostephanus truncatus (Horn) and the maize weevil, Sitophilus zeamais Motschulsky continue to cause tremendous losses to stored maize. Research in the UK has identified Beauveria bassiana, IMI 389521 as a suitable control agent for grain storage pests in the UK. The pathogenicity of B. bassiana, IMI 389521 was evaluated against adult P. truncatus, S. zeamais and Teretrius nigrescens in Ghana. Fifty adults of each insect species were treated with 0.5 g dry conidia powder of this isolate at 8.65 × 108 conidia/g for 1 minute and mortality recorded daily for 14 days. The results indicated that B. bassiana, is pathogenic against P. truncatus and S. zeamais, inducing over 90% mortality by day 7. Teretrius nigrescens was, however less susceptible to the fungus with 30% mortality. To determine the most effective concentration of B. bassiana for the control of P. truncatus, a laboratory dose response experiment using four concentrations of B. bassiana (108–1011 cfu/kg maize) was also conducted. Maize grains (250 g) in separate jars were treated with the four concentrations of the product. Fifty adults of P. truncatus were placed into the jars containing the treated maize and mortality was assessed weekly for 3 weeks. The most effective dose was 1010 cfu/kg maize, which resulted in 96% and 100% mortality of P. truncatus after 2 and 3 weeks, respectively. This study shows that B. bassiana could effectively be integrated into bio-control programme of these two key pests of maize in Ghana after further field trials