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Ngueguim J.R.,Institute Recherche Agricole pour le Developpement IRAD | Betti J.L.,CITES | Riera B.,French Natural History Museum | Ambara J.,CITES | And 2 more authors.
Forest Science and Technology

Pericopsis elata is a timber tree with a high commercial value used as hardwood in the Congo basin forest. It is considered a threatened species by the International Union for Conservation of Nature (IUCN) and classified in 1992 in the annex II of the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES). The natural regeneration of P. elata is problematic; an increase in knowledge concerning its ecology, productivity, and potentials could significantly contribute to the sustainable exploitation of the species and improve its silviculture. Despite the irregularity of silvicultural treatment, Kienke south and Ndeng ndeng plantation, respectively situated in the south and east region of Cameroon, show acceptable survival rates. These rates are estimated at 91% in parcel P75 planted at 884 stems/ha and 69% in parcel P746 with a density of 192 stems/ha. Tree mortalities were mainly attributed to edaphic and climatic factors. The best performances of tree diameter growth were observed in parcel P741 and P73 where the mean diameters at breast height of trees were 27±18 cm and 24±11 cm. The higher values of standard deviation showed a strong variability within tree diameter in the parcels. In P741, the mean annual growth decreased from 1.40 cm/year to 0.7 cm/year between 1979 and 2009. The tree diameter structures of the plantations are asymmetric with a very high slope before the modal class expressing the difficulties of the growth of individuals with diameter lower than 10 cm. The production of wood was estimated at 1326.6±70 m3 for trees with more than 30 cm diameter. The plantations are situated out of the natural and geographical area of the species; this can justify the low performances of trees growth. The survey of these plantations and silvicultural treatments could contribute to increasing tree growth. © 2012 Korean Forest Society. Source

Ngueguim J.R.,Institute Of La Recherche Agricole Pour Le Developpement Irad | Ngueguim J.R.,University of Yaounde I | Zapfack L.,University of Yaounde I | Youmbi E.,University of Yaounde I | And 4 more authors.
Biotechnology, Agronomy and Society and Environment

Trees plantation of Mangombe is situated in rain forest of low altitude. Six plots among which one of Mansonia altissima (A.Chev.) A.Chev., 2 of Lovoa trichilioides Harms, 3 of Terminalia ivorensis A.Chev. and one perturbed natural forest are concerned by this study. The work consisted to the evaluation of the floristic diversity under canopy in order to appreciate the influence of forest plantation on natural regeneration. A total of 26 families, 42 genders and 46 species were censured. Meliaceae and Apocynaceae are present in all the plots. In plot one of T. ivorensis, M. altissima and natural forest, the low value of equitability of Pielou traduces the dominance of flora by few species and the transitory situation of the ecosystem. On contrary the rest of plots present a good repartition of individuals among the species. One can notice a weak organization of the ecologic system in M. altissima plot, this corresponds to favourable conditions of environment for installation of many species represented by a few number of individuals. Shannon indices, relatively low in plot one of T. ivorensis characterize an ecosystem where one species is dominant. Globally, the regeneration under canopy is reconstituted progressively and remains less diversified than the nearest natural forest. Creation of genetic pool through selective entertainment under canopy will permit polycyclic management of plots for sustainable production of wood. Source

Mouen Bedimo J.A.,Institute Of La Recherche Agricole Pour Le Developpement Irad | Cilas C.,CIRAD - Agricultural Research for Development | Notteghem J.L.,Montpellier SupAgro | Bieysse D.,CIRAD - Agricultural Research for Development
Crop Protection

Arabica coffee production in Africa is greatly affected by coffee berry disease (CBD), caused by Colletotrichum kahawae. This disease is specific to green berries and leads to 60-80% harvest losses under conditions conducive to the development of the pathogen. Agricultural practices, combined with chemical control involving 8-12 annual fungicide applications, are known to be very effective against CBD, especially in high altitude regions (>1600. m) where the most damaged coffee farms are found. Temperatures and rainfall may be key factors in the development of CBD epidemics. Therefore, an epidemiological study was conducted on smallholding coffee farms in Cameroon, to assess the dependence of disease development on variations in these climatic factors. Cross-correlations between disease severity and climatic parameters recorded weekly were estimated over two successive years (2004-2005), revealing a significant increase in disease severity in line with decreasing temperatures (minimum or maximum). They also indicated a large variation in disease severity depending on the number of raining days during berry growth. However, no significant correlation was found with the quantity of rainfall over the two years of observations. Thus, temperatures and rainfall distribution appear to be the key climatic parameters that favor the development of CBD epidemics. These results suggest that temperature and rainfall parameters might be very useful for establishing predictive models to optimize effective CBB control in areas with a high disease incidence. © 2011 Elsevier Ltd. Source

Jemo M.,International Institute Of Tropical Agriculture | Nolte C.,International Institute Of Tropical Agriculture | Tchienkoua M.,Institute Of La Recherche Agricole Pour Le Developpement Irad | Abaidoo R.C.,International Institute Of Tropical Agriculture
Nutrient Cycling in Agroecosystems

Biological nitrogen fixation (BNF) potential of 12 soybean genotypes was evaluated in conditions of low and sufficient phosphorus (P) supply in two acid soils of southern Cameroon. The P sources were phosphate rock (PR) and triple superphosphate (TSP). The experiment was carried out during two consecutive years (2001 and 2002) at two locations with different soil types. Shoot dry matter, nodule dry matter, and nitrogen (N) and P uptake were assessed at flowering and the grain yield at maturity. Shoot dry matter, nodule dry matter, N and P uptake, and grain yield varied significantly with site and genotypes (P < 0.05). On Typic Kandiudult soil, nodule dry matter ranged from 0.3 to 99.3 mg plant-1 and increased significantly with P application (P < 0.05). Total N uptake of soybean ranged from 38.3 to 60.1 kg N ha-1 on Typic Kandiudult and from 18 to 33 kg N ha-1 on Rhodic Kandiudult soil. Under P-limiting conditions, BNF ranged from -5.8 to 16 kg N ha-1 with significantly higher values for genotype TGm 1511 irrespective of soil type. Genotype TGm 1511 can be considered as an important companion crop for the development of smallholder agriculture in southern Cameroon. © 2008 Springer Science+Business Media B.V. Source

Begoude A.D.B.,University of Pretoria | Begoude A.D.B.,Institute Of La Recherche Agricole Pour Le Developpement Irad | Gryzenhout M.,University of Pretoria | Wingfield M.J.,University of Pretoria | Roux J.,University of Pretoria
Antonie van Leeuwenhoek, International Journal of General and Molecular Microbiology

Native Terminalia spp. in West Africa provide a popular source of construction timber as well as medical, spiritual and social benefits to rural populations. Very little is, however, known regarding the diseases that affect these trees. During an investigation into possible diseases of Terminalia spp. in Cameroon, orange to yellow fungal fruiting structures, resembling those of fungi in the Cryphonectriaceae, were commonly observed on the bark of native Terminalia ivorensis, and on dead branches of non-native Terminalia mantaly. In this study the fungus was identified based on morphological features as well as DNA sequence data (ITS and β-tubulin) and its pathogenicity was tested on T. mantaly seedlings. Our results showed that isolates of this fungus represent a previously undescribed genus in the Cryphonectriaceae, which we describe as Aurifilum marmelostoma gen. et sp. nov. Pathogenicity tests revealed that A. marmelostoma is pathogenic on T. mantaly. These tests, and the association of A. marmelostoma with disease symptoms on T. ivorensis, suggest that the fungus is a pathogen of this important tree. © 2010 Springer Science+Business Media B.V. Source

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