Functional Diversity of Mycorrhizal Fungi Has Differential Effects on Salinity Tolerance of <i>Acacia seyal</i>(Del.) Seedlings

Acacia seyal is a leguminous plant that plays an important role in the ecosystem of Sahelian zone by producing gum, wood and fodder. The growth of A. seyal is subject to many constraints as salinity which can affect the development of this tree. Therefore, soil microorganisms can help A. seyal to better tolerate the effects of negative environmental stresses. The contribution of arbuscular mycorrhizal fungi (AMF) to the salt tolerance of A. seyal, was evaluated by testing the effects of eight different arbuscular mycorrhizal fungi (AMF) isolates in the performance of A. seyal seedlings subjected to different levels of salinity (0, 340 and 680 mM). The results based on growth parameters of shoot and root parts, shoot mineral N, P, K and Na content as well as survival rates and mycorrhization showed that AMF improved mineral nutrition of A. seyal seedlings during salt stress. The combination between AMF and salinity provided evidence that the efficiency of AMF isolates were variable in improving mineral nutrition and mortality rate for A. seyal seedlings related to the level of salt stress. However, the effects of inoculation were variable depending to the AMF isolate associated with seedlings and the level of salinity, suggesting that interactions between plants and AMF can be modulated by both AMF diversity and the type and level of abiotic factors. Rhizophagus intraradices was more efficient at 680 mM NaCl in plant growth and mineral uptake while Glomus deserticola did not promote a better plant development than most of the other species inoculated to seedlings.

Maize Crop N Uptake from Organic Material of <i>Gliricidia sepium </i>Coinoculated with <i>Rhizobium</i>and Arbuscular Mycorrhizal Fungus in Sub-Saharian Africa Sandy Soil

The effect of green manure of gliricidia (Gliricidia sepium (Jacq.) Walp) leguminous plants applied for cereal maize cultivation and N uptake by cereal were investigated and analyzed in relation to influence of dual inoculation of gliricidia with microbial symbionts. Two pot experiments were conducted in greenhouse. The first trial was set up to enhance growth of gliricidia with exotic and indigenous rhizobial strains and arbuscular mycorrhizal fungus and the second to determine the effect of gliricidia organic material on maize growth. Direct 15N-labelling techniques were used to estimate N-fixed by gliricidia plant and N uptake of maize cereal crop from green manuring was calculated. Growth of gliricidia trees estimated by aboveground biomass production and N fixed were positively affected by dual inoculations. This study showed that shoot dry weight and N accumulation of maize cultivated under gliricidia green manure were influenced by its application and indirectly by microbial treatments. The N recovery by the maize accounted 17.32% to 26.52% of N applied as gliricidia organic material. Gliricidia green manure N accumulation and release, and afterward microbial inoculations were substantially determining on maize crop N uptake and growth in sandy soil of Sub-Saharian Africa.