Abstract
Pot experiments were conducted under greenhouse conditions to evaluate the symbiotic efficiency and host range of several Rhizobium isolates on woody tree legumes and cross-nodulation between local Acacia trees grown in Central Saudi Arabia. The results indicated that Acacia trees varied in their ability to form symbiotic relationships with the Rhizobium isolates. Depending on their nodulation responses to isolates, three groups of Acacia were recognized. The first group presented nodulation with more than one of the isolates and formed real nodules with most of the Rhizobium species. The second was composed of trees with ineffective nodules with most of the isolates. The third group failed to form nodules with the tested Rhizobium. Acacia saligna and A. tortillis were the most tree species, having effective nodules with all isolates. Rhizobium isolates KSA6, KSA8 and KSA9 were able to cross-nodulate A. tortillis, A. saligna and A. gerrardii as well as their own hosts. Seedlings of A. tortillis and A. saligna inoculated with isolates of KSA6 and KSA8 showed levels of growth and biomass more than those of inoculated ones with isolates of KSA9. The Rhizobium isolates KSA6 and KSA8 can be utilized to enhance productivity in afforestation programs in the central region of Saudi Arabia. (C) 2016 Friends Science Publishers.