Rice grains can be attacked by a range of pathogens, including Aspergillus species, which can cause the accumulation of aflatoxins and represent a serious threat to the consumers. Aflatoxins are secondary metabolites synthesized by Aspergillus species and naturally occur in various foodstuffs. In this study, we sought to analyze the prevalence of aflatoxin-producing Aspergillus spp. in rice grains currently sold in Kenyan local markets. We analyzed a total of 98 samples randomly collected and primarily analyzed to observe moisture content and fungal growth. We then isolated Aspergillus species, characterized them morphologically and using the Internal transcribed spacer (ITS) primers. Finally, we screened them for aflatoxin-producing isolates targeting Norsolorinic Acid (nor-1) and Versicolorin (ver-1) specific genes involved in aflatoxin biosynthesis. We observed that all tested samples were contaminated. The highest prevalence of Aspergillus species and aflatoxigenic fungal species, had values of 66% and 36.4% for nor-1 and ver-1, respectively. In total, 66% of all isolates were confirmed to be aflatoxin producers. The occurrence of high contamination levels of Aspergillus species points to the possibility of production of aflatoxins in rice grains. This work provides a baseline for future studies on the occurrence of mycotoxigenic fungal species in rice grains being sold in local markets and strategies to control these aflatoxigenic strains at pre- and post-harvest levels.

Cocoa is an important crop in Cameroon, where it is cultivated in different areas, including marginal areas, characterized by a rather low level of annual rainfall and marked dry seasons. In order to release cocoa varieties with a good level of adaptation to these marginal conditions, nine full-sib progenies, already released to farmers in other producing areas of the country, were assessed on twelve on farm cocoa plots, set up in 2006, in Mbam et Inoubou county, which is a forest–savannah transition zone. The traits assessed were mortality rate, yield and yield stability. Mortality rate and yield vary widely among trial plots and among progenies. Four out of the nine assessed progenies present a yield level significantly higher than the five others. The lowest level of yield stability (estimated by the contribution to total ecovalence) was observed in both the highest and the lowest yielding progenies. Recommendation for the large-scale release of these progenies to farmers of the county, and to other cocoa producing forest–savannah transition areas, are made, based on the results obtained from this study.

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.

Ralstonia solanacearum is a major constraint in tomato production. The aim of this work was to identify the different biovars and races of R. solanacearum which infect tomato plants in Cameroon and determine the most virulent in a gnotobiotic environment. Thirty (30) samples were collected in the field of 03 different agro-ecological zones considered as major tomato production area in Cameroon. The bacteria were isolated on modified Kelman solid medium, and identified based on morphological and biochemical characterization. The pathogenicity test was performed in a gnotobiotic environment by root inoculation. Twenty-nine (29) isolates showed colonies characteristic of virulent strains. Water, motility, catalase, KOH, Kovac oxidase, glucose reduction, and sucrose tests were positive. However, gram staining, spore production, arginine test and sulfate reduction were negative. The biovar tests carried out revealed the presence16.66% biovar 2 (bv 2) and 76.66% biovar 3(bv 3). The tobacco hypersensitivity tests carried out revealed the presence of two (02) races: race 1 and race 3 (majority). A predominance of race3 biovar 3 was observed in Cameroon. Results from pathogenicity test revealed that two (02) strains, FM6 (race 3 bv2) and BFo (race 3 bv 3) were high virulent, causing up to 100% loss of seedlings on the sixth day post-inoculation.

This study was aimed at determining whether variations in oil palm annual yields were significantly influenced by years of production, and at establishing if so simple and multiple linear regression relationships between oil palm annual yields and yearly climatic variables. Climatic and yield data were gathered in three locations (Bota-Limbe, Dizangué and Kienké) of the coastal zone of Cameroon, within the oil palm estates of three agro-industrial corporations. Yearly climatic variables were recorded for a period of 23 consecutive years (1990-2012); oil palm annual yields of five plots in each location were also recorded for the same period. Variations in annual yields (in metric-tons of bunches per hectare) were significantly influenced (P˂0.05) by years of production. Only a few yearly climatic variables however were significantly correlated with annual yields (none of the climatic variables in Bota-Limbe; evapotranspiration and rainfall height in Dizangué and insolation in Kienké). Low but significant, simple and multiple linear regressions were established that contributed to explain 18.10 to 54.60% of annual yields. Other mathematical relationships for more accurate predictions must be built, as for example curvilinear regressions; for linear regressions may not be sufficient to explain annual yields in their completeness. © 2015 International Formulae Group. All rights reserved. Keywords: Evapotranspiration, insolation, rainfall height, variations, predictions, mathematical relationships

Pythium myriotylum is a telluric Oomycete, the causal agent of cocoyam root rot disease. In Cameroon, it can cause crop losses of up to 100% without sanitary measures. The aim of this study was to evaluate the antifungal efficacy of bioactive compounds from Thevetia peruviana (yellow oleander) and Azadirachta indica (neem) sub-fractions obtained by GC/MS against P. myriotylum. The antifungal activities of crude extracts (2%; 1%; 0.5% (m/v)) of T. peruviana and A. indica (2% and 0.5% (m/v)) in water, methanol and acetone were evaluated. The sub-fractions resulting from the roughing of the most active fractions by VLC (Vacum Liquid column) were characterized by GC/MS and their minimum inhibitory concentrations (MIC) were determined, as well as their mode of action on P. myriotylum. The results obtained show that GC/MS analysis identified many compounds with antifungal activities such as Oxime-, methoxy-phenyl, Hexadecanoic acid, methyl ester; 9,12-Octadecadienoic acid, methyl ester, (E,E); 7-Octadecenoic acid, methyl ester; 9-Octadecenoic acid, methyl ester, (E); Methyl stearate, Phenol, 2,2’-methylenebis[6-(1,1-dimethylethyl)-4-methyl. All fractions derived from crude extracts significantly reduced the growth of P. myriotylum compared with the negative control, with the highest inhibition rates obtained with the aqueous ethyl acetate phase fractions (87.77% and 100% for T. peruviana and A. indica, respectively). The most active sub-fractions F1 of VLC2 and F4 of VLC1 inhibited the pathogen’s protein synthesis. The lowest MICs were obtained with sub-fractions F1 of A. indica and F4 of T. peruviana (0.166% and 0.0837%). T. peruviana and A. indica can be considered as potential substitutes for chemical control.