In Africa, rice is produced and is a source of food energy in most developing countries. But its cultivation faces to brown spot disease, caused by Bipolaris oryzae (Breda de Haan) Shoemaker, which is a serious seed-borne and seed transmitted disease of rice worldwide.The aim of this study was to screen rice varieties for resistance to brown spot disease in field conditions inYaoundé. A completely randomized Fisher block design with three repetitions was used during 2 growing seasons (2015 and 2016). Growth, yields and disease (incidence and severity) parameters were evaluated on four rice varieties (Nerica 3 and 8, White rice and Kamkou). Results show that height of the Nerica 8 variety (86.03cm) and the number of tillers of Kamkou variety (21.66) were significantly highest compared to others varieties (P<0.05) at 59 Days After Sowing (DAS). There was no significant difference on disease incidence for the different rice varieties at the end of rice plant cycle. However disease severity was lower on Nerica 3(2.71%) and Nerica8 (2.05%) varieties and higher on White variety (4.57%). Hence, Nerica 3 and 8 varieties were more tolerant to brown spot disease than others varieties. Overall, Nerica 3 (3.68 t ha-1) and Kamkou (3.51 t ha-1) varieties resulted in higher yields than white rice 28.93 t ha-1.

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.