Impact of wood cuts on the structure and floristic diversity of vegetation in the peri-urban zone of Ngaoundere, Cameroon

The main objective of this paper was to study the impact of various wood cuts on the structure and the floristic diversity of the savannas, and to seek for durable solutions against deforestation during a four year investigation. An inventory of the woody layer on 120 sites areas of 50 × 50 m showed that savannas have structures in "L". This structure translate the state of the degradation of the vegetation. The floristic diversity showed that the characteristic species of the degradation of the shrubby savannas area are Hymenocardia acida, Piliostigma thonningii and Annona senegalensis, and those of the wooded savannas are Daniellia oliveri and Cesalpinia sp. It was also shown that highest wood cuts are depressive for the stability of the savannas and for the disappearance of the vegetable biodiversity. Consequently, they are responsible for the acceleration of the degradation and the alarming installation of the desert in wet savannas of Ngaoundéré. A measure of co-administration between the government and the bordering population must be therefore encouraged to protect and safeguard the anthropized vegetation

Evaluation des lignées endogames de maïs (Zea mays L.) pour le développement des hybrides adaptés aux zones de basse et moyenne altitudes du Cameroun

Un croisement diallèle a été utilisé pour évaluer 11 lignées endogames de maïs (Zea mays L.) de basse et moyenne altitudes dans le développement des hybrides. Les 55 hybrides issus de ce croissement et 3 variétés composites ont été évalués en 2004 sur trois sites dans un dispositif simple comprenant 2 répétitions. Les objectifs étaient d’identifier les hybrides les plus productifs, d’étudier les effets de gènes des lignées et d’évaluer les aptitudes à la combinaison. L’analyse de la variance combinée sur les trois sites a montré que les différents hybrides ont présenté le même comportement et classement relatif d’un site à l’autre pour le rendement. Cinq hybrides à savoir Cam Inb gp117 x ATP-S4-25W, 91109x ATP-S4-25W, 88094 x cml 254, 88094 x Exp24 et 87036 x cml 254 se sont mieux comportés que le meilleur hybride de l’IRAD (87036 x Exp24). Les lignées de basse altitude ont montré les meilleures performances en croisements dans les deux zones. L’effet de la dominance n’a pas été significatif tout comme l’aptitude spécifique à la combinaison sur les trois sites. Cependant, l’aptitude générale à la combinaison a été significative et en générale positive. Les caractères sont donc contrôlés par les gènes à effets additifs.Mots clés : Aptitude à la combinaison, dominance, effet des gène

Impact of organic and inorganic fertilizers on tomato vigor, yield and fruit composition under tropical andosol soil conditions

Introduction. Little is known about the impact of organic manure on andosol. Materials and methods. Two varieties of Solanum lycopersicum L. (cvs. ‘Rio grande’ and ‘Rossol VFN’) were grown under tropical andosol. The soil was silty, acidic and very poor in Bray P (3 mg·kg–1) with a strong imbalance in the (Ca:Mg:K) ratio of (74.0:25.0:0.7). Five fertilization treatments were used: (i) control with no fertilizer, (ii) minerals, with a (Ca:Mg:K) ratio of (76:18:6) and 75 mg P·kg–1 of soil; (iii) poultry manure with a (Ca:Mg:K) ratio of (68:24:7) and 450 mg P·kg–1 of soil; (iv) a combination of (ii) and (iii), and (v) mineral fertilization as applied by local farmers, with a (Ca:Mg:K) ratio of (73:25:1) and 54 mg P·kg–1 of soil. Results. All cation-balanced treatments (organic, mineral or a combination of both) significantly improved plant growth, the number of trusses and fruits per plant, the marketable fruit yield and fruit P, K, Ca and Na contents of both tomato varieties considered. The ‘Rio grande’ variety was the most productive (32–44 t·ha–1) compared with the ‘Rossol’ variety (20–22 t·ha–1). There was no major difference between the organic fertilizer and the cation-balanced mineral fertilizer. There was no effect of mineral fertilizer with an unbalanced cation composition on tomato plant growth and production as compared with unfertilized control. Conclusion. In tropical andosol poor in potassium and phosphorous and with excess of Mg, application of poultry manure in adequate dosage and at the right time is capable of sustaining tomato fruit production, as well as the application of calculated inorganic fertilizer

Viabilité et développement végétatif des plantules de piment (Capsicum annuum L.) suivant différents matériels de conditionnement des semences

Germination and Seedling Development from Pepper (Capsicum annuum L.) Seeds following Storage in Different Packaging Materials. A study on the germination and seedling development from pepper (Capsicum annuum L.) seeds following storage in different packaging materials was carried out at the Institute of Agricultural Research for Development (IRAD), Njombe Multipurpose Research Station in Cameroon. Germination tests were conducted at 30 days intervals during 24 weeks of seed conservation in the laboratory at ambient temperature. Seeds were prepared from 4 pepper varieties (Safi, Big sun, Thailande and Local) and stored in 5 packaging materials (glass vial, plastic vial, laminated aluminium foil packet, paper and plastic envelope). The experiment was laid out in a 4 x 5 factorial design (4 varieties of pepper x 5 packaging materials) making 20 treatments in 5 replications. At each germination test, germinated seeds were counted everyday during 15 days. To estimate seedling development, 5 seedlings from each pepper variety issued from each packaging material was grown during each germination test in a polythene bag filled with local topsoil. Each sample was repeated 10 times. Thirty days after sowing, observations were made on seedling development parameters. The results obtained show that germination rate is higher immediately after seed preparation for all pepper varieties. Thereafter germination rate declines slowly when seeds are stored in laminated aluminium foil packets and rapidly when they are stored in paper and polythene envelopes. The other packaging materials occupy intermediary positions. Also, seedlings issued from seeds stored in laminated aluminium foil packets are more vigorous than those issued from seeds stored in paper and polythene envelopes during seed conservation period (6 months). The rapid loss of viability in pepper seeds stored in the two last packaging materials could be attributed to their permeability to air and humidity which accelerates seed ageing and deterioration

Evaluation of the sensitivity of two plantain varieties essong and big ebanga to the nematode Radopholus similis

Plantains are among the crops that enhance food security in Cameroon. However, plantain yields remain low because of several constraints of parasites such as Radopholus similis, a nematode that can cause losses up to 75% in fields when no protection measures are taken. In most cases, the sensitivity of local plantain varieties to R. similis is unknown; which generally results to low yields despite the control technique used. This limits their up scaling in the country. This work was undertaken to study the sensitivity of two varieties, Essong and Big Ebanga, to R. similis. To this effect, the parasitic activity of R. similis on the varieties Essong and Big Ebanga was assessed in vivo. The variety Grande naine known to be very sensitive to R. similis was used as the control. According to the results obtained, local varieties Essong and Big Ebanga were found to be sensitive to R. similis with the variety Essong being the most sensitive.Key words: Musa spp., banana plantain, nematode, Radopholus similis, sensitivity

Mosquito development in a macrophyte-based wastewater treatment plant in Cameroon

Abstract Macrophyte-based wastewater treatment systems are recognized as an alternative for sewage purification in developing countries. Unfortunately, they also represent a favorable breeding ground for mosquitoes, thus a serious drawback that should be addressed despite the good promise of this technology. A 1-year study of mosquito production in seven ponds of a Pistia stratiotes-based domestic wastewater treatment plant in Cameroon revealed that approximately 43 imagoes/m 2 per day rose up, among which 54% were female. Mansonia and Culex were the main breeding genera with about 55 and 42% of the total imagoes respectively. Culex bred mostly in the first three ponds (B1-3), characterized by a high organic pollution. Mansonia occurred in great number in the later ponds (B4-7), where the water quality was rather better and the roots of P. stratiotes well developed, thus permitting the fixation of a great number of larvae to the macrophyte roots. Though representing a favorable breeding ground for mosquitoes, only 0.02% of captured imagoes were Anopheles gambiae, suggesting that this wastewater treatment plant does not significantly contribute to the development of the malaria vector in this area

Artificial infestations of Tapinanthus ogowensis (Engler) Danser (Loranthaceae) on three host species in the Logbessou Plateau (Douala, Cameroon)

In Cameroon today, Loranthaceae has become a major pest against which a great "battle" must be launched if food production in the country has to be maintained at a self-sufficient level. However, an effective battle against pests can only be achieved through a better understanding of their geographical distribution and biology. Eight Loranthaceae species (Globimetula braunii, Globimetula dinklagei, Globimetula opaca, Helixanthera mannii, Phragmanthera capitata, Tapinanthus globiferus, Tapinanthus ogowensis, and Tapinanthus preussii) have been identified in the Douala area. Among these species, T. ogowensis is the only one limited to a surface area of about eight hectares in the Logbessou plateau located in a direction of North-East from Douala (Latitude 03°40 -04°11' N, Longitude 09°16' -09°52' E, and at an altitude of 13 m). In this zone, the hemi-parasite infests only one host tree (Dacryodes edulis) in the orchards, gardens and agricultural plantations. The hemiparasite is however common and adapted to all the different ecological regions in the southern part Cameroon where it infests several host trees. In order to study the stages involved in the germination, fixation, as well as the initial stages involved in the development of the seedlings of T. ogowensis, three of the most frequent host species (D. edulis, Mangifera indica and Persea americana) on the plateau were artificially infected. The results revealed that the host species are sensitive to the parasite, T. ogowensis, at least during their early stages of growth and development. D. edulis is the most sensitive host species with a 22% yield of young seedlings as against 5 and 4% for P. americana and M. indica, respectively. This sensitivity of the mango tree to T. ogowensis had never been demonstrated before. The percentages of seeds germinating on the different host species however remained high; 96% on both D. edulis and M. indica and 93% on P. americana. It was also revealed that the development of the young seedlings of T. ogowensis is greatly influenced by the availability of light, a plausible reason why Loranthaceae occupies mainly the uppermost branches of the oldest trees found here