Survival and Susceptibility of Rhizobium meliloti to Desiccation in Some Southern Iraqi Soils

Studies to estimate the population of Rhizobium meliloti in southern Iraqi soils showed that samples, containing no detectable R. meliloti, occurred in all soils tested. The results showed that the numbers were influenced by soil salinity. The numbers were 0.64 × 10² g⁻¹ in soil with high salts concentration (E.C. = 9.6 mmhos/cm), compared with 2.80 × 103 g⁻¹ in soil with low salinity (E.C. = 3.1 mmhos/cm).Four different isolates of R. meliloti (5 M, 2 M, 2 Q, and 4 H) were obtained by using antibiotic-resistant technique. A comparison was made of the survivability of isolates, grown in dry sand and in yeast extract mannitol broth (YMB), adjusted with glycerol to lower water activities. The results showed that R. meliloti isolates 5 M and 2 M could better survive than other isolates in dry sand and in YMB at an aw value of 0.980.