Inoculation of diazotrophic bacteria and arbuscular mycorrhizal fungi on the cassava crop

Abstract

The versatility of the cassava crop (Manihot esculenta Crantz) to adapt to low fertility soils, although plants require high levels of nutrients, has been related to the occurrence of arbuscular mycorrhizal fungi (AM) and diazotrophic bacteria. One experiment was then performed with micropropagated plants, to evaluate the effects of AM fungi and diazotrophic bacteria on cassava growth and nutrition. The experiment was performed in pots of 3.5 L capacity, with sandy disinfected soil as substrate. Inoculation with diazotrophic bacteria did not show any statistically significant positive effect, while the inoculation with AM fungi and co-inoculation of AM fungi and bacteria favored growth and nutritional parameters. Co-inoculation of AM fungi and Bacterium E increased shoot and root dry weight up to 50% and 105%, respectively, in relation to the bacterium alone. Synergistic effects were also observed in the nutrient content, increasing shoot and root N up to 88% and 173%, and P content up to 83% and 158%, respectively. Co-inoculation of Bacterium E with Glomus clarum also increased mycorrhizal colonization by 40% and sporulation up to 168%, in comparison to the fungi alone. These beneficial effects suggest that the stimulus could be both by the increase in plant nutrient uptake as well as by the stimulation of colonization by MA fungi.