Production, storage and costs of inoculum of arbuscular mycorrhizal fungi (AMF)

Abstract

Arbuscular mycorrhizal fungi (AMF) inoculation may contribute to the development of sustainable agriculture. Inoculation requires production and storage of inocula in a commercial scale, and few protocols have been developed for this purpose. AMF inocula were produced in an aeroponic system, and their infectivities were tested after storage for 3, 6, and 10 months, at room temperature (28 °C) or at 4 °C, in substrates composed of sand, sand + expanded clay, or sand + vermiculite. Sweet potato plants, previously grown in soil + sand for 90 days and mycorrhized by Claroideoglomus etunicatum and Glomus clarum, were transplanted to the aeroponic system and harvested after 120 days. The density of glomerospores of both AMF per gram of roots in the aeroponic system was much higher than per gram of soil in pots, facilitating handling and storage of the inocula. Storage at room temperature resulted in decreased infectivity of the inocula in all substrates after 6 months, while storage at 4 °C in sand + vermiculite and sand + clay maintained the viability (>59 % infectivity) even after 10 months. The costs of production to inoculate one seedling pot with C. etunicatum and with G. clarum were R$ 0.98 (US$ 0.41) and R$ 3.07 (US$ 1.30), respectively, and should be reduced in a commercial system. With an adequate infectivity (>25 %) and relatively low production costs these inocula can be recommended as biofertilizers.