Morpho-Physiological and Biochemical Characterization of Soybean-Associated Rhizobia and Effect of Their Liquid Inoculant Formulation on Nodulation of Host Plants in the Cameroon Cotton Fields Zone

The aim of this research was to assess the diversity of the Cameroon cotton zone in soybean associated rhizobia in order to formulate the most efficient elite inoculant to boost both the cotton and soybean production. Therefore, soybean associated rhizobia were isolated and characterized morphologically, physiologically and biochemically on YEMA culture media. For each of the two soybean varieties (Houla1 and TGX1910 14F) used, the trials were laid out in two IRAD-fields of North Cameroon (Sanguere-Paul) and Far-North (Soukoundou) respectively, under a complete randomized complete block design, the isolate formulations representing the treatments. The six isolated strains (IS1, IS2, IS3, IS4, IS5, IS6) from which seven liquid inoculant were formulated were revealed to belong to the same slow growing group of rhizobia, with a high level of tolerance to temperature, pH, and salinity, with optimum growth at respectively 28˚C, pH (7 - 9), salt (1% - 5%). Not surprisingly, root nodules were formed by both inoculated and uninoculated soybean plants. However, the most efficient soybean-rhizobia symbiosis for nodulations were isolate IS6 associated to TGX1910 14F variety, and isolate IS5 associated to Houla1variety at Sanguere-Paul. Whereas isolate M was associated to TGX1910 14F variety, Houla 1 variety had affinity with native rhizobia isolates at Soukoundou. The present results suggest the adaptability of rhizobia isolates to a particular soybean variety at a particular cotton fields zone. These findings should be taken into consideration for commercial inoculant formulation.

Food supplementation by an invasive fleshy-fruited shrub sustains body condition of a native frugivorous bird during winter

Birds tend to adjust their behavior and physiology to changes in food availability in their environment.Season­al fluctuation of food resources may act as an energetic challenge,augmenting hypothalamus-pituitary-adre­nal axis(HPA axis)activity,leading to an increase in corticosterone concentrations and promoting the metab­olism of energy stores.Plant invasions may alter seasonal food fluctuations by providing a food supply during scarce seasons.This could attenuate the energetic challenge,reducing HPA axis activity and the metabolism of reserves.Using a system with seasonal fluctuation in food availability,we tested if fruit supplementation by the invasive fleshy-fruited Pyracantha angustifolia during the season of native fruit scarcity decreases the con­sumption of energy stores through activity attenuation of the HPA axis.We measured changes in body condition and circulating corticosterone(CORT)concentration in Turdus chiguanco occurring at sites both invaded and not invaded by P.angustifolia over 3 time periods that correspond to the periods prior to,during and after high­est fruit production of the plant.Fruit scarcity in the ecosystem appears as an energetic challenge for T.chiguan­co,given that body mass,fat score and residuals of body mass/tarsus length decreased during winter in a site not invaded by the exotic shrub.Conversely,the presence of the invasive plant seemed to attenuate the metab­olism of energetic reserves,as we did not record changes in body condition in birds inhabiting the invaded site.Unexpectedly,plasma CORT concentration did not vary between sites or periods.Further evaluation is required to elucidate how enhanced body condition,resulting from the consumption of a fleshy-fruited invasive plant,af­fects survivorship and reproductive performance in T.chiguanco.