COINOCULATION OF BLACK LOCUST WITH RHIZOBIUM AND GLOMUS ON A DESURFACED SOIL

Abstract

Seedlings of black locust (Robinia pseudoacacia L.) were coinoculated with a local effective strain Rhizobium species RpI1 and with Glomus deserticola. The effects of both symbioses on plant growth were studied in a greenhouse experiment with four treatments: two single inoculations, one double inoculation, and no inoculation, in a nonsterilized substrate from a desurfaced soil. A synergic effect was observed because double inoculation produced significantly higher shoot biomass, nodule biomass, and N2 fixation, as measured by the acetylene reduction assay (at least 93%, 50%, and 192%, respectively) than any single inoculation treatment and than noninoculated controls, which were nodulated by soil-born rhizobia. Mycorrhizal colonization did not improve the growth of control plants, but it did significantly improve the specific nitrogenase activity of plants inoculated also with Rhizobium species RpI1 by 77%. We conclude that prenodulation of plants is necessary for better growth on harsh substrates and that mycorrhizal colonization helps nodulated plants reach their P demand in P-limited soils.