Victor Désiré Taffouo

Myrmecofauna of cocoa trees infested by Loranthaceae genus Phragmanthera in Sodecao seed fields of Nkoemvone (South of Cameroon)

The present study was carried out in order to identify the ant fauna of cocoa fields leeched by Loranthaceae, genus Phragmanthera in Nkoemvone seed farms in the South region of Cameroon. The collection of ants was conducted between November 2013 and January 2014. A total of 15 ant species divided into two sub families (Formicinae and Myrmicinae) have been identified, the subfamily of Myrmicinae being the most represented with 8 genera and 13 species. Fourteen of the 15 ant species harvested, were found on infested cocoa trees. Tetramorium aculeatum has emerged as the most abundant ant species on infested cocoa trees with an index of Berger-Parker dominance equal to 0.32 and 0.34 for cocoa parasitized by Phragmanthera capitata and Phragmanthera nigritana, respectively. Key words: Ants, inventory, cocoa plants parasitized, Loranthaceae, Cameroon.

Influence of mycorrhization and phosphate fertilizer on growth of Voandzou ( Vigna subterranea (L.) Verdc.)

Many strains of arbuscular mycorrhizal fungi (AMF) have the ability to improve the water and mineral nutrition of plants and in particular the supply of phosphorus (P). The objective of this study was to determine the influence of mycorrhization and simple superphosphate (SSP) on growth of Voandzou, also called Bambara groundnut ( Vigna subterranea (L.) Verdc.). Five SSP doses (0, 30, 60, 90 and 120 mg P 2 O 5 .kg -1 of substrate) were administered on seedlings of two Voandzou landraces inoculated with AMF composite ( Gigaspora margarita and Acaulospora tuberculata ). Plants were harvested eight weeks after sowing. The results showed that mycorrhization and SSP favored vegetative growth and increased biomass. Thus, the number of leaves of mycorrhized plants was significantly higher than that of control by 5.0%. The highest leaf P-content was observed with 60 mg P 2 O 5 + AMF treatment; but was reduced with 120 mg P 2 O 5 + AMF treatment. Mycorrhizal intensity was highest without SSP. High P levels were observed to reduced mycorrhizal efficiency. However, low SSP doses could be associated with AMF to optimize Voandzou growth. In conclusion, mycorrhization and SSP enhance the growth of Voandzou.

Effect of phosphorus fertilization on arbuscular mycorrhizal fungi in the Bambara groundnut rhizosphere

Tropical soils are highly leached, abundantly clayey and strongly acid, resulting in low mineral availability and especially phosphorus (P). The plants of this region must establish symbiotic relationships enabling them to strengthen their hydromineral nutrition. The aim of this work was to study the effect of P fertilizer application on the diversity of arbuscular mycorhizal fungi (AMF) under the rhizosphere of three Bambara groundnut (Vigna subterranea) landraces. To attain it, plants were grown in farm under different simple superphosphate (SSP) levels (0, 50, 100, 150 and 200 kg.ha-1 P2O5) in 2015 at Mendong and Soa districts. Experimental units were arranged in a randomized complete block design with three replications. Soil and root samples were taken from the rhizosphere of three randomly selected seeds holes per experimental unit at flowering (31 days after sowing) and fruition stages. At harvest, the roots were stored in 50% ethyl alcohol. They were stained with methyl blue and observed under an optical microscope. The soil samples allowed the trapping to be carried out in a greenhouse with sorghum as test plants. Results show that Bambara groundnut landraces were the host of several AMF species and were highly colonized with all showing hyphae, vesicles and even spores. High level of SSP (200 kg.ha-1 P2O5) significantly (p<0.001) reduced the intensity of mycorrhization as well as the diversity indices compared to the control. A density of AMF spores reaching 1930 was obtained in 100 g of trapping substrate. On the basis of morphological characteristics, 16 AMF species belonging to nine genera (Glomus, Acaulospora, Gigaspora, Racocetra, Rhizophagus, Funneliformis, Septoglomus, Diversispora and Claroideoglomous) were isolated and identified. Rhizophagus intraradices and Septoglomus constrictum were the most abundant. AMF species identified in this groundnut rhizosphere can be multiplied and used as biological fertilizer to increase its yield. Key words: Arbuscular mycorhizal fungi (AMF) diversity, Cameroon, morphological characteristics, rhizosphere, root colonization, spore density, symbiosis, phosphate fertilization, Voandzou.