Response of cowpea (Vigna unguiculata) to inoculation with co-selected vesicular–arbuscular mycorrhizal fungi and Rhizobium strains in field trials

After initial screening in sterilized and nonsterilized soils, two vesicular–arbuscular mycorrhizal (VAM) fungi (Glomus pallidum Hall and Sclerocystis microcarpa Iqbal & Bushra) and two compatible cowpea rhizobial strains (JRC14 and JRC29) have been co-selected. The response of cowpea (Vigna unguiculata (L.) Walp) to inoculation with co-selected pairs of VAM fungus and Rhizobium strains was field tested in Jamaica at two locations (soil types sandy clay loam and bauxitic silt loam). Dual inoculations of cowpea increased the pod yield, mycorrhizal infection, nodule formation, and shoot P and N content compared with single inoculations of either VAM fungus or Rhizobium. However, JRC14 when paired with G. pallidum or S. microcarpa showed maximum yield increase (45%) in both soil types. Our work suggests that appropriate pairing of VAM fungus – Rhizobium should be used for field inoculation. Key words: cowpea, rhizobia, mycorrhizal fungi.