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Soil salinity has a negative impact on crop production over the world. The effect of salt stress on growth, chlorophyll content, mineral distribution, biochemical constituents and non-enzymatic antioxidant compounds of white yam (Dioscorea rotundata (L) var. gana) cultivar regularly consumed in Cameroon were investigated. Plants were subjected to four different levels concentrations of NaCl (0, 50, 100 and 200 mM), with 0 mM NaCl as a control. The supply of intake doses of NaCl in the culture medium significantly (P < 0.001) decreased the dry biomass (roots and shoots), growth parameters (number of leaves, noose diameter, leaf area and stem height) and chlorophyll contents from 100 mM NaCl. Mineral elements (K, Ca and Mg) and K/Na ratio significantly (P < 0.001) decreased in roots and shoots with increasing salinity. The higher sodium (Na) concentrations were recorded in shoots than in roots. The different biochemical constituents (proline (PRO), total soluble carbohydrates (CH), soluble proteins (PR) and total free amino acids (FAA)) and non-enzymatic antioxidants compounds (total phenolic (TP) and flavonoids (FLA) contents) significantly (P < 0.001) increased from 50 mM NaCl. The main strategy in cv. gana seems to increase osmotic adjustment through high accumulation of CH, PR, FAA and PRO in the leaves and they could eventually be considered as biochemical indicators of early selection and osmotic adjustment ability for salt tolerant plants. The gana variety could be encouraged to be planted on salt affected soils for the better development in salty areas.

A field experiment was conducted in Bambili, North West Region of Cameroon to evaluate the morphological and agronomic parameters of potato grown in soil treated with two organic manures as well as soil physico-chemical properties. A randomized complete block design (RCBD) with three treatments (EM manure, IMO manure and control), and four replications was conducted. Results showed significant differences (P ≤ 0.05) in the height of plants and leaf area index throughout the period of experiment in plants treated with both manures. IMO manure produced taller plants (65.150 ± 17.850 cm) compared to EM manure (57.642 ± 12.146 cm) and the control plants (19.070 ± 4.215 cm). The highest leaf area index was recorded by plants treated with IMO manure followed by those treated with EM manure, and then the control. The fresh weight of tubers produced by IMO manured plants (241.64 ± 32.94 g) was higher than those of EM manured plants (227.62 ± 44.58 g), and control (125.66 ± 31.63 g). Both IMO and EM manures had significant positive effects on soil physico-chemical properties, morphological parameters, and yields. However, IMO manure had better effects. Soil physico-chemical properties revealed a decrease in electrical conductivity, total phosphorus, calcium content and magnesium content. IMO treated soil recorded the higher rate of decrease, followed by EM treated soil and control soil, total organic carbon increased while total nitrogen content did not change during experiment for manure soils.

Colocasia esculenta (L.) Schott is an important food for millions of people in countries of Africa, Asia andCentral America. The cultivation of taro suffers from an epidemic disease, the taro mildew, caused by P. colocasiae, which is a disease that manifests itself as oily and circular spots on tubers, stems, petioles and on taro leaves causing losses of more than 50% in less than ten days. This study was carried out to evaluate the impact of this pathogen on the leaf area parameter in two varieties of taro (Ibo coco and Atangana) at different water levels, then evaluate the incidence of the disease severity on the leaves at different water levels and study the behavior of this pathogen on plants previously inoculated with arbuscular mycorrhizal fungi (AMF) of the genus Gigaspora magarrita and Acaullospora tuberculata. The plants were separated into three batches (control batch not infected, batch infected with pathogen and batch not only infected but also inoculated with AMF at different water contents (500 ml, 370 ml, 250 ml and 125 ml), the batch infected with the pathogen alone showed a reduction in the growth parameters compared to the control, and the inoculated and infected batch also showed a reduction in growth parameters but closer to the control. In addition, the speed of propagation of the lesion in the inoculated batch is reduced compared to that of the uninoculated batch, and this speed also decreases with the water content, as a result of which the mildew of taro develops easily. Moreover, the addition of AMF makes it possible to minimize its propagation.

Influence des sols salins et calcaires sur la croissance, la nutrition minérale et les composantes agronomiques du niébé dans trois zones agro écologiques du Cameroun