Response of lentil under controlled conditions to co-inoculation with arbuscular mycorrhizal fungi and rhizobia varying in efficacy

This study assessed the co-inoculation response of lentil (Lens culinaris cv. Laird) to arbuscular mycorrhizal fungi (AMF) and effective and ineffective Rhizobium leguminosarum bv. viceae strains. Plants were inoculated with the AMF species Glomus clarum NT4 or G. mosseae NT6 and/or nine Rhizobium strains varying in efficacy, and grown for 110 d in soil containing indigenous AMF and rhizobia. The effectiveness of the Rhizobium strains on the N nutrition of 6-week-old lentil grown under gnotobiotic conditions was correlated (P < 0.045; r = 0.64) with the N nutrition of 110-d-old lentil grown in natural soil. The growth and yield responses of lentil to co-inoculation with AMF and Rhizobium strains depended on the particular AMF-Rhizobium strain combination. In some cases, the productivity of lentil inoculated with an effective Rhizobium strain was significantly (P < 0.05) reduced by an apparently incompatible AMF species compared to the Rhizobium treatment. In contrast, the yield of lentil inoculated with some ineffective Rhizobium strains was significantly (P < 0.05) enhanced by an apparently compatible AMF species compared to the Rhizobium treatment. However, maximum lentil productivity was achieved only in treatments with effective Rhizobium strains or co-inoculation treatments with effective Rhizobium strains and a compatible AMF species. Correlation analyses indicated that total shoot dry matter production was significantly (P < 0.05) correlated with the total shoot N (P < 0.0001; r = 0.94) and P content (P < 0.0001; r = 0.96), indicating that this response was mediated by enhanced N and P nutrition. Furthermore, a (P < 0.05) positive relationship between AMF colonization of roots and total shoot dry matter production (P < 0.0187; r = 0.43), N (P < 0.0116; r = 0.45) and P content (P < 0.0183; r = 0.43) of shoots was also noted. Our results suggest that synergistic interactions between AMF and Rhizobium strains can enhance lentil productivity.