Improving germination indices of alfalfa cultivars under saline stress by inoculation with beneficial bacteria

Salinity stress is one of the most significant factors affecting seed germination of alfalfa. In this study, we considered whether it is possible to reduce the deleterious effects of salinity by inoculating seeds with beneficial salt-tolerant bacteria. Seeds of nine alfalfa cultivars were inoculated with two beneficial bacteria, Pseudomonas sp. Proradix and Hartmannibacter diazotrophicus. Salinity stress reduced the germination indices in all nine alfalfa cultivars significantly. Inoculation with either bacteria could improve germination performance through increasing germination percentage, germination index, radicle length, plumule length, seed vigour and seedling fresh weight. Germination indices decreased in most cultivars at >10 dS m(-1) salt concentration (without inoculation), but were high at 20 dS m(-1) (inoculation with either bacteria). Germination indices were improved by both the bacteria, however, germination percentage, germination index, plumule length and seed vigour were most improved by inoculation with Pseudomonas sp. Proradix; seedling fresh weight and radicle length were most improved by Hartmannibacter diazotrophicus. It is suggested that the bacteria could be used to inoculate alfalfa seeds and solve the problem of germination under saline conditions.