Single inoculation with arbuscular mycorrhizal fungi promotes superior or similar effects on cowpea growth compared to co-inoculation with Bradyrhizobium

Abstract

• The single inoculation of R. clarus and C. etunicatum promoted the accumulation of nitrogen in the aerial part of both cultivars. • Inoculation with C. etunicatum resulted in higher phosphorus content in the shoot of the BRS Guariba cultivar. • Plants inoculated with C. etunicatum had similar or superior performance to plants fertilized with NPK or P. This study evaluated the efficiency of arbuscular mycorrhizal fungi (AMF) and the effect of co-inoculation with Bradyrhizobium on mineral accumulation and growth of two cowpea cultivars. The experimental design was a 12 × 2 factorial arranged in a completely randomized design, with four replications. The first factor consisted of 12 nutrient treatments: one control, four with AMF ( Rhizophagus clarus and Claroideoglomus etunicatum , inoculated individually and as a mixture, and AMF-based commercial inoculum) and four with AMF + rhizobia ( Bradyrhizobium sp. BR 3262); the second factor included two cowpea cultivars (BRS Novaera and Guariba), totaling 96 plots. Morphophysiological traits of plants, nitrogen and phosphorus accumulation in the aerial part, and symbiotic efficiency of microorganisms were evaluated. Double inoculation with C. etunicatum and R. clarus and the co-inoculation with Bradyrhizobium had no effect on height, shoot dry mass and N contents in the shoot of cowpea when compared to single inoculation with AMF. Positive effects of co-inoculation with Bradyrhizobium were verified for root dry mass in the treatments CE+B.BR 3262 and RC+CE+B.BR 3262, and for chlorophyll index and phosphorus content of the cultivar BRS Novaera in the nutrient treatment RC+CE+B .BR 3262. The nutrient treatment with single inoculation of R. clarus and C. etunicatum promoted the accumulation of nitrogen in the shoot for both cultivars. For the BRS Guariba cultivar, inoculation with C. etunicatum also resulted in higher phosphorus content. Overall, plants inoculated with C. etunicatum had a performance similar or superior to plants fertilized with NPK or P, resulting in greater mycorrhizal efficiency, which may be an alternative to conventional fertilization for cowpea cultivars BRS Novaera and BRS Guariba.