Chickpea is the most important food legume and ranks
third in terms of total global production (Singh et al. 1998).
This legume is also the most important crop in Iran and
annually 700,000 hectares are sown with chickpea
(Sabaghpour et al. 2006). Chickpea can fix atmospheric
nitrogen through its symbiosis with rhizobia and increases
the input of combined N2 to the soil. Therefore, this legume
has beneficial effect on productivity of cereals and other
crops in agricultural rotations (Herridge et al. 1995). Yield
potential of this legume depends on the rhizobial association
and plant genotype, together influencing the symbiotic
performance (Mhadhbi et al. 2004). Symbiotic nitrogen
fixation in legumes is limited by environmental stresses,
mainly salinity and drought, resulting in decreased yielding
capacity (Serraj et al. 1999; Zahran 1999). Therefore,
recognition of drought tolerance mechanisms of legumes is
important in order to improve their agronomic performance.
However, it is difficult to find ways to reduce
drought-induced stress because response of legumes to
drought stress varies depending on the studied legume
species. An important involvement of the rhizobial strain
and plant genotype in the symbiosis performance under
unstressed and stressful conditions has been also suggested
in several reports (Mhadhbi et al. 2004, 2008, 2009; Sadiki
and Rabih 2001). Thus, the selection of effective rhizobial