Isolation and Authentication of Local Rhizobia Nodulating Common Bean (Phaseolus vulgaris L.) in Different Agro-Ecological Zones of Côte d’Ivoire

Legumes such as common bean (Phaseolus vulgaris L.) have been introduced into cropping systems for sustainable soil management. Consequently, the loss of fertility of the latter remains a major constraint to bean production because this legume is rarely fertilized, yet it is considered to be a poor nitrogen fixer in the absence of inoculation. To overcome this, this study was undertaken with the objective of seeking efficient local rhizobia in order to propose a bean inoculum formulation. To do this, soil samples taken from twelve localities in the Centre, North and West areas of C?te d’Ivoire were used to trap bean nodulating rhizobia. The ROBA1 bean accession used was sown in pots containing the sampled soils. Seedlings were uprooted at the start of flowering and nodulation was assessed. The isolates obtained were purified and then characterized phenotypically. The infectivity and symbiotic efficacy of these isolates were determined in vitro by the authentication test in which the purified isolates were reinoculated to their original host plant. A total of 24 rhizobium isolates were obtained from the soils of six localities. During morphological characterization, the isolates showed typical characteristics of Rhizobium. With the exception of RPC501, RPC505 and RPC522, all isolates were authenticated and able to nodulate the host plant in controlled culture. Isolates RPC502, RPC507, and RPC508 were effective and significantly increased (P < 0.05) nodule number and weight, height, and plant biomass. This study has, therefore, revealed the presence of effective local rhizobia in Ivorian soils and capable of nodulating common beans. A genetic characterization of efficient rhizobia identified after experimentation in different environmental conditions should be considered before being recommended as bean rhizobia inoculant.

HLA-G 3’UTR 14 bp Insertion Is Associated with a Decreased Risk of Developing Human African Trypanosomiasis in the Côte d’Ivoire Population

Human African trypanosomiasis (HAT), or sleeping sickness, caused by Trypanosoma brucei gambiense, is associated with diverse clinical outcomes. Host’s genetic factors involved in immunity are potential factors that can regulate infection. Genetic polymorphisms within HLA-G could influence the level of HLA-G expression and therefore play a critical role in infection outcomes. The goal of our study was to investigate the association of 14 bp Indel HLA-G polymorphism with the susceptibility/resistance to HAT. DNA samples were collected from 119 cases, 221 controls and 43 seropositive individuals living in Ivorian HAT foci. The 14 bp Indel polymorphism was determined by PCR. Homozygous individuals for 14 bp insertion had a lower risk of progressing to active HAT (p = 0.012, OR = 0.27, 95% CI: 0.09 - 0.8). Moreover, the frequency of 14 bp insertion homozygous genotype was higher in the seropositive group (11%) than in the HAT cases group (3%) (p = 0.043, OR = 0.27, 95% CI: 0.07 - 0.99), which suggested a protective effect of 14 bp insertion homozygous genotype. Genetic polymorphisms in HLA-G may be associated with a variable risk to develop HAT. The 14 bp insertion appears to favour the occurrence of long-lasting T. b. gambiense latent infections.