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This study aims to evaluate the antifungal activities of methanolic and aqueous extracts of Thevetia peruviana seeds on the in vitro growth of Phytophthora colocasiae. A randomized sample block design containing four treatments (T-: absolute control, AE, ME and Callomil Plus at the dose of 12.5 μL/ml) with three repetitions was used. Plant extracts were used at three concentrations: C1: 12.5 µl/ml; C2: 25 µl/ml and C3: 50 µl/ml. The study took place in the University of Yaoundé 1, Faculty of Sciences, Department of Plant Biology, Laboratory of Phytopathology and Crop Protection, and in the Institute of Agricultural Research for Development (IARD) of Yaoundé, Laboratory of Phytopathology, during the year 2019-2020. Aqueous and methanolic extracts of T. peruviana were prepared and used at the concentrations of 12.5, 25 and 50 μL/ml. P. colocasiae was isolated from infected taro leaf cultivars "Macumba/Ibo coco" located in three different regions in Cameroon: West, Littoral and Centre. The different leaf explants of taro were put in V8 agar medium and maintained in pure culture. Mycelial fragments of P. colocasiae of about 0.8 cm in diameter were cut and placed in sterile Petri dishes containing Potato Dextrose Agar (PDA) medium supplemented with different concentrations of plant extracts and incubated at 23±1°C for seven days for the evaluation of the radial growth. Methanolic and aqueous extracts have completely inhibited the growth of West and Littoral strains at 25 μL/mL while total inhibition of the pathogen was not obtained with strain of Centre region. The lowest inhibition was obtained with the strain of Centre region (85.1%) for aqueous extract and (70.95%) for methanolic extract compare to 100% for West and Littoral region at highest concentration. The aqueous extract at the concentration of 25 μL/ml totally inhibited the in vitro radial growth of some strains of P. colocasiae. This extract, active against P. colocasiae could be used as alternative to fungicides for the control of taro leaf blight. In other hand, the strain of Littoral region was most sensible to extracts than the others. This strain could be used to provide a genetic resource for future trials in natural conditions in greenhouse and in the field.

Background: Cercospora leaf spot disease of okra whose pathogen is Cercospora malayensis causes yield losses of up to 60% in plantations. To limit productivity losses, fungicides are commonly used, but are expensive and degrade the environment. Aims: This study aims to test in vitro efficacy of Annona muricata seed extracts against Cercospora malayensis. Study Design: Four extracts were used in this study (the ethyl acetate, acetone, methanol and aqueous extract of A. muricata seeds at the concentrations C1 = 7.5 μl/ml, C2 = 15 μl/ml, C3 = 30 μl/ml and C4 = 60 μl/ml as well as the synthetic fungicide at the concentration of 3.33 g/l) in triplicate. The phytochemical screening of the extracts was performed, the radial growth of pure explants (7 mm diameter) of C. malayensis deposited in sterile Petri dishes containing the PDA medium supplemented with the different concentrations of extracts and incubated at 23 ± 1°C for 6 days were evaluated. Minimum inhibitory concentrations (MIC50, MIC90) were calculated. Results: The extracts of A. muricata seeds are rich in tannins, flavonoids, terpenoids and phenols. The ethyl acetate extract at the concentration C3 resulted in 100% total inhibition of growth of C. malayensis in the Petri dishes. The other extracts resulted in total inhibition of the growth of C. malayensis at C4. The low MIC50 values (12.9 and 21 μl/ml) were obtained with the ethyl acetate and acetone extract, respectively. The ethyl acetate and aqueous extract at the C4 concentration were found to be fungicidal. Conclusion: The extracts were found to be potential fungicide against the C. malayensis strain and might be an alternative in the fight against fungal diseases of okra as their activity was comparable to that of the synthetic fungicide Monchamp 72 WP.

Maize is a major crop grown and consumed in the world and it requires a high fertilizer input. Although chemical fertilizers are an important input to get higher crop productivity, they have an impact on soil fertility, environment and human health. A field study was carried out to find alternatives to the mineral fertilization of maize. The aim of this study was to determine the influence of fertilizers on maize growth and yield while evaluating economic profitability. Four treatments (control, compost, poultry manure and mineral fertilizer NPK 20-10-10) and two maize varieties (local variety and improved variety CMS 8704) were used in a split-plot design with four replicates. Physicochemical analyses of soil and organic fertilizer were determined. Growth parameters, yield and acceptability index were evaluated. As results, poultry manure and compost are rich in nitrogen and phosphorus. At 9 weeks after sowing (WAS) the best stem diameter was obtained by the local variety in the plots fertilized with mineral fertilizer (2.83±0.31 cm). The yield of the CMS 8704 variety was significantly higher in the plots fertilized with poultry manure (2.23 t ha-1) than the yield of the local variety in the control plots (1.16 t ha-1). Principal component analysis (PCA) shows that compost and poultry manure were characterized by an increase in growth parameters as well as mineral fertilizer NPK. Poultry manure had the highest acceptability index of 1.25. In view of these results, it is clear that organic fertilizers; especially poultry manure, would have a positive impact on increasing maize production.

Asian rust caused byPhakopsora pachirhizi, which is a major constraint to production of soybean, causing 90% yield losses in field. Synthetic fungicides used to control this disease are environmentally degrading and have negative impact on the health of producers and consumers. The use of resistant soybean genotypes can be an effective control alternative. The aim of this work is to evaluate the tolerance of soybean varieties to Asian rust disease under natural conditions. Forty-three soybean varieties were screened using a completely randomized block design with three replicate. Incidence and severity of disease at 6, 8 and 10 weeks after sowing (WAS) and yields were evaluated. Results show that disease incidence of Asian rust was significantly higher in the local variety R3 (16.67%; 29.63%; 75.93%) at 6, 8 and 10 WAS respectively. At 6 and 8 WAS severity of disease was higher in local variety R3 (21.17% and 24.14% respectively). The variety TGX-2010-12F has the highest yield (1.17 t ha-1) than the local variety R3 (0.17 t ha-1). Principal component analysis realized with incidence, severity of disease at 6, 8, 10 WAS and yield shows that 12 varieties are highly susceptible to Asian rust, 12 varieties are moderately resistant, and 19 varieties are susceptible. This study shows that Asian rust attacks all soybean varieties in the field. Moderately resistant varieties, can be advised to growers with appropriate protection methods or be subject to varietal improvement through genetic techniques.