Nutritional changes induced by fungi on cowpea (Vigna unguiculata L. Walp) seeds

Seeds are usually infected by microorganisms and pests during storage, causing deterioration and reduction in the nutritive and market value of these seeds. In this study, the proximate composition of Vigna unguiculata seeds inoculated with different fungal organisms was determined to ascertain the level of deterioration caused by fungi on the seeds. The fungi used in the study were Botryodiplodia theobromae, Fusarium oxysporum, Rhizopus stolonifer and Aspergillus niger. There was a significant increase (p<0.05, 0.008) in the protein content of seeds inoculated with fungi. Fusarium oxysporum (29.45%) caused the highest increase in protein followed by Aspergillus niger (28.14%), Botryodiplodia theobromae (27.85%) and Rhizopus stolonifer (27.50%). The increase could be attributed to the proteineous content of the fungal mycelia. There was a significant increase (p<0.05, 0.005/0.014) in moisture and ash content of inoculated seeds respectively. Fusarium oxysporum caused the highest increase in ash (7.93) while Rhizopus stolonifer (5.4) caused the lowest increase. The increase in ash content is due to the presence of minerals like potassium and phosphorus in the mycelia of the fungi. There was a significant decrease (p<0.05, 0.019) in the carbohydrate, lipid, fibre and dry matter content of fungi-inoculated seeds when compared with the control. Fusarium oxysporum (36.6) caused the highest decrease while Rhizopus stolonifer (43.2) caused the lowest decrease in dry matter of inoculated seeds. Decrease in dry matter may be as a result of production of enzymes by these fungi.

Efficacité in-vitro des extraits aqueux, éthanoliques et des huiles essentielles de Chromoloena odorata et d’Ageratum conyzoïdes sur le développement des champignons responsables des pourritures de cabosses de cacaoyers (Theobroma cacao L.)

La présente étude se propose d’étudier l’efficacité des extraits aqueux, éthanoliques et des huiles essentielles de Chromolaena odorata et d’Ageratum conyzoïdes sur le développement des champignons responsables des pourritures des cabosses de cacaoyers dans les plantations villageoises d’Akonolinga, Dizangué et Tonga. Les extraits ont été obtenus par macération de 100 g de poudre de chaque plante. Les huiles essentielles obtenues par centrifugation ont été fixées par le sulfate de sodium anhydre. Trois milieux de cultures V6, V8 et le milieu Pomme de terre – Dextrose - Agar (PDA) ont été fabriqués pour la culture des champignons associés aux cabosses. Les extraits et huiles essentielles de plantes ont été préparés aux concentrations de 5 ; 10 ; 15 et 20 mg/ml. L’essai a été conduit suivant un dispositif en blocs complets aléatoires avec 3 répétitions. La fréquence d’isolement de chaque champignon par localité, la surface des lésions développées sur les cabosses infectées et le pourcentage d'inhibition PI (%) des champignons pathogènes ont été mesurés et soumises à l’analyse de la variance (ANOVA). Les moyennes obtenues ont été séparées par le test de Duncan au seuil de probabilité 5%. Les résultats suivants ont été obtenus : sur 8 espèces isolées, seulement Phytophtora megakarya, Botryodiplodia theobromae et Colletotrichum gloeosporioides. ont été pathogènes sur les cabosses saines. L’analyse statistique a montré des différences significatives (à P ≤ 0,05) entre les surfaces des lésions causées par ces champignons sur les cabosses entre le 4ième, 7ème et 10ème jour après inoculation (JAI) en fonction des espèces fongiques testées. Les extraits aqueux de C. odorata et d’A. conyzoides à la concentration de 20 mg/ml ont présenté des pourcentages d’inhibition à 100 % sur P. megakarya, B. theobromae et C. gloeosporioides. Les extraits éthanoliques et les huiles essentielles ont inhibé le développement de B. theobromae, de C. gloeosporioides et de P. megakarya à 100 % aux concentrations de 15 et 20 mg/ml. Les extraits et huiles essentielles de C. odorata et d’A. conyzoïdes pourraient donc être utilisés pour lutter contre les champignons responsables des pourritures de cabosses de cacaoyers.Abstract This work is to evaluate the antifungal activity of Chromolaena odorata and Ageratum conyzoides on the development of mycoflora associated with cocoa pods diseases in villager plantations in Akonolinga, Dizangue and Tonga. Extracts were obtained by steeping of 100 g of powder of each plant. Essential oil extractions were done through centrifugation. Essential oil were fixed by sulfate of sodium anhydre. Three culture media V6, V8 and Potato Dextrose Agar (PDA) were made to cultivate mycoflora associated with cocoa pods Data were randomized into completely blocs with three replications. Frequency of each fungus per locality, lesion area developed on cocoa pod by fungi and percentage of inhibition PI (%) of each fungus were being submitted in variance analysis. Means were separated by Duncan test with (P ≤ 0, 05). The results showed that: over 8 varieties of fungal species isolated from cocoa pods, unly Phytophthora megakarya, Botryodiplodia theobromae and Colletotrichum gloeosporioides were pathogens on cocoa pod inoculated. The analysis of the variance showed significatives differences (P ≤ 0, 05) of area lesions on cocoa pods between the 4th, 7th and the 10th days after inoculation. Mycelia growth was stopped at the concentrations of 20 mg/ml for aqueous extracts, of 15 and 20 mg/ml ethanolic extracts and essential oil. .The extracts and essential oil of C. odorata and A. conyzoides can be used to fight against micoflora associated with cocoa pods disease.

Occurrence of Postharvest Fungal Rots of Sweet Potato (Ipomoea batatas (L) Lam.) in Southwest Nigeria and their Control with Sawdust Extracts

A study was conducted in three agroecological zones (AEZs) of Southwest, Nigeria to evaluate the incidence and pathogenicity of postharvest fungal rots of sweetpotato and their control with extracts of sawdust from some tropical trees. Survey of rotted tubers was conducted in 18 markets across the three AEZs: humid rainforest (HF), derived savannah (DS), and southern guinea savannah (SGS). Fungi associated with rotted tubers were isolated, identified and their pathogenicity determined. In vitro fungitoxicity of Anogeissus leiocarpus, Gmelina arborea and Cola nitida sawdust extracts were assessed in an experiment laid out in a Completely Randomized Design (CRD) with 3 replicates. Six fungi species found to be associated with rot on tubers were Botryodiplodia theobromae, Rhizopus stolonifer, Aspergillus niger, Trichoderma viride, Penicillium oxalicum and Fusarium oxysporum. Highest (35%) rot incidence was observed in HF zone with R. stolonifer as the most prevalent. Botryodiplodia theobromae was most prevalent (68.75%, 54.54%) in SGS and DS zones respectively. All the six isolated fungi were pathogenic to sweetpotato but induced varying levels of rot severity. Botryodiplodia theobromae, R. stolonifer or A. niger induced complete (100%) rot of inoculated tubers. Sawdust extracts reduced mycelial growth of test pathogens at three sawdust concentrations (50 g/L, 75 g/L and 100 g/L) tested. Inhibition of fungal growth increased with extract concentration. Anogeissus leiocarpus sawdust extract at 100 g/L exhibited highest range of mycelial growth inhibition (8.80 - 73.0%) across tested pathogens. Gmelina arborea sawdust extract at 100 g/L significantly inhibited (p<0.05) mycelial growth of B. theobromae, P. oxalicum and T. viride while C. nitida exhibited strong fungitoxicity to F. oxysporum at 100 g/L. Application of the sawdust extracts at 50 g/L, 75 g/L and 100 g/L concentrations has the potential to minimize postharvest fungal rot of sweetpotato.

Anti-microbial Effect of Cocoa Leaf Extracts on Botryodiplodia theobromae; Leading Causative Organism of Crown Rot Disease of Banana (Musa acuminata)

An investigation was carried to assess in-vitro management of crown rot disease on Banana using extracts of cocoa leaves. The causative organism (Botryodiplodia theobromae) was sub cultured and the concentration determined through microbial count. Different cocoa leaves extracts were prepared using two different solvents. A conventional fungicide known as Mancozeb was used as a positive control and the nutrient broth only served as negative controls to help in assessment of the antimicrobial effect of the cocoa leave extracts. Phenolic Methanol Extracts (PME), Crude Cocoa Leaves Aqueous Extracts (CCAE) and Mancozeb were employed to prepare aqueous solutions through serial dilution with varied concentration. The nutrient broth (100 µL of double strength), 100 µL each of the plant extract concentrations, and 20 µL of inoculums were dispensed in a sterile micro-titre plate containing 96 wells. Incubation of the micro-titre plate was carried out at a temperature of 37°C for 1 day (24 hours). Susceptibility or otherwise of the microorganism (B. theobromae) from four sample stations was analyzed with 20 µL of a 5% solution of 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide MTT. The presence of blue-black wells indicated the growth of B. theobromae. The experiment was conducted in triplicates for PME (refined), CCAE and Mancozeb. The minimum inhibition concentrations (MICs) of PME (refined) that inhibited the growth of B. theobromae collected from four different locations were 5mg/ml, 2.5 mg/ml, 10 mg/ml and 2.5 mg/ml respectively for B. theobromae (B1)(Offinso), B. theobromae (B2)(Effiduase), B. theobromae (B4)(Kejetia) and B. theobromae (B5)(Ejisu) which was lower compared to the MICs of CCAE which was 30 mg/ml for the four sample stations. Comparatively, the MIC of the PME (5 mg/ml, 2.5 m g/ml, 10 mg/ml and 2.5mg/ml) was almost equivalent to the MIC of the conventional fungicide (Mancozeb) (2.5 mg/ml) for all the four sample stations of B. theobromae.

Antagonism Test of Trichoderma atroviride and Gliocladium sp. Bali Local Isolates As a Disease Control of Blendok Disease (Botryodiplodia theobromae) in Grapefruit (Citrus grandis L. Osbeck)

This study aims to determine the ability of Trichoderma atroviride and Gliocladium sp. in inhibiting the fungus that causes Gumosis disease Botryodiplodia theobromae. This study used a completely randomized design with two single treatments and was repeated eight times. In the in-vitro antagonism test Trichoderma atroviride and Gliolcadium sp. can inhibit the fungus Botryodiplodia theobromae as well. The percentage of inhibition was 94.58% in the Trichoderma atroviride antagonism test and 81.67% in the Gliocladium sp. antagonism test. Whereas the Botryodiplodia theobromae Colony Area had no significant effect on both treatments. Each Botryodiplodia theobromae Colony area is 18.34 cm2 with T. atroviride treatments and 22.25 cm2 with Gliocladium sp. treatment. The growth rate of Botryodiplodia Theobroma fungi was superior to that of Trichoderma atroviride and Gliocladium sp.

Diagnosis of Dieback Disease of the Nutmeg Tree in Aceh Selatan, Indonesia

Effective control disease measures require a great deal of knowledge about the pathogen, which is also applied to dieback disease of the nutmeg tree in Aceh Selatan District, Province of Aceh, Indonesia. The objectives of this study were to identify the causal agent of dieback disease on a nutmeg plantation and to assess the effect of drought stress on the development of dieback disease. Pathogen identification was carried out by observing the symptoms of infected plants, morphological characters of the isolated pathogens, Koch’s postulates, and molecular analysis and pure pathogen cultures. The samples were taken from an infected part of the nutmeg plant (twigs, stems, and roots) in 6 subdistricts at the center of the nutmeg plantation in Aceh Selatan. Koch's postulates were performed by using the mycelia of pathogens on 1-year-old nutmeg seedlings. Drought stress was simulated everyday, and then once every 2 weeks, to study the effect of drought stress on dieback. The results showed that there were 4 genera of fungal pathogens (Botryodiplodia theobromae, Fusarium solani, Graphium euwallaceae, and Rigidoporus microporus) out of 6 fungi associated with dieback disease. However, B. theobromae Pat. turned out to be the dominant fungi associated with dieback on the nutmeg tree in Aceh Selatan. Drought stress was proven to be a predisposing factor for explaining this problem epidemic in Aceh Selatan.