Reparation of aged lettuce (Lactuca sativa) seeds by osmotic priming and Azospirillum brasilense inoculation

Although Azospirillum spp. are considered to be important plant growth promoting bacteria, their possible effects on germination and vigor of aged lettuce seeds has not been previously evaluated. In fact, there is a paucity of published data about inoculation effects on seed germination. The aim of this work was to evaluate seed quality of oneyear aged lettuce (Lactuca sativa L. cv. Crimor INTA) seeds after Azospirillum brasilense Sp245 inoculation with or without an osmopriming pretreatment. Fresh lettuce seeds were stored in the dark in a dry chamber for one year and then subjected to inoculation with A. brasilense Sp245, to osmotic priming with 0.37 mol/L MgSO4, or to both combined treatments. Seed germination, seed vigor, and seedlings emergence percentages were determined, and the abnormal seedling fraction was characterized. Azospirillum brasilense inoculation without a previous osmopriming enhanced seed vigor and seedling emergence percentages and decreased the fraction of abnormal seedlings. There was an additional effect of osmopriming as a previous treatment on germination percentage. We concluded that the use of A. brasilense inoculation alone or after an osmopriming treatment would contribute to overcome the negative effects of ageing on lettuce cv. Crimor INTA seeds.