Biological nitrogen fixation of Biserrula pelecinus L. under water deficit

The present work studied the effects of water deficiency conditions on the biological nitrogen fixation of three na tive rhizobia (SafPt12, SafPt6, and AjuPt16) isolated from Biserrula pelecinus L., and a reference strain Mesorhizobium ciceri biovar biserrulae. In terms of plant-water status, B. pelecinus showed typical signs of drought avoidance strategies such as reducing the aboveground development (i.e. reduction in leaf surface area and increase in root/ shoot ratio) in detriment of a better developed root system. Dry-matter production and nitrogen content of the aboveground biomass decreased with the increasing levels of drought stress, as well as nodulation and symbiotic nitrogen fixation, for all the tested isolates. The parameters investigated suggested that SafPt12 was the most suc cessful native rhizobia to withstand severe water conditions without compromising nitrogen fixation demands.