Soumaya Tounsi-Hammami, Sana Dhane-Fitouri, Zied Hammami, Christine Le Roux, Faysal Ben Jeddi
The excessive use of chemical fertilizers, principally N-fertilizers, causes unanticipated environmental impacts, adversely affecting the environment and the human health. Finding environmentally sustainable methods of improving productivity of plants with reducing the use of chemical fertilizers is a current challenge in the field of agricultural research globally. Against this background, this work aimed at studying the effects of a mixture of three PGPR- bacteria namely Agrobacterium sp. previously selected for their multi-PGPR-traits, on yield components and nutrient content in grains of durum wheat under natural conditions. A field experiment was performed in four different sites located in arid and semi-arid Tunisian areas. In each environment the bacterial mixture was applied to soil at the emergency wheat stage with decreasing levels of N fertilization (100%, 50% and 0% of the full dose: 150Kg/ha). At maturity, yield components were recorded. Nitrogen and phosphorous content were analyzed in wheat grains. The inoculation with bacterial mixture increased the yield components as well as the nutrient contents in wheat grains compared to uninoculated plants. However, the efficiency of this mixture depends strongly on the applied dose of N-fertilization. At 50%N, the application of the mixture resulted in significant increases in number of spike (26-75%), grain yield (34- 70%), biomass yield (22-71%), nitrogen content (10-16%) and phosphorous content (29-47%) in grains. Interestingly, these increases resulted in attaining values statistically higher than those observed in control plants receiving 100%N in all the environments. The use of a mixture of multi-traits-PGPR strains offers an opportunity to improve yield and grains quality of durum wheat. Moreover, it helps to reduce 50% of the chemical nitrogen fertilization.