Mycorrhizal dependency of passion fruit ( <i>Passiflora edulis</i> f. <i>flavicarpa</i> )

Abstract

Mycorrhizal dependency of passion fruit (Passiflora edulis f. flavicarpa). Abstract — Introduction. Brazil is one of the most important producers of passion fruits. Inoculation with arbuscular mycorrhizal fungi (AMF) may reduce or eliminate the need for phosphate fertilization on this crop. We investigated the response of passion fruit seedlings to inoculation with AMF and phosphorus (P) supply. Materials and methods. A greenhouse experiment was carried out in a factorial design. The seedlings were inoculated with 100 spores per plant of single or mixed AMF inoculum on sterilized or non-sterilized soil which was amended with (11 or 30) mg P 〈 dm -3 soil applied as superphosphate or used unfertilized (4 mg P 〈 dm -3 soil). Relative mycorrhizal dependency (RMD) of passion fruit was estimated for each treatment of inoculation, soil sterilization, and P level, by expressing the difference between the dry mass of mycorrhizal plants and non-mycorrhizal plants as a percentage of the dry mass of mycorrhizal plants. Results. Inoculation was effective only on plants grown in sterilized soil with (4 or 11) mg P 〈 dm -3 soil. Plants were facultatively mycotrophic when associated with AMF and when receiving a supply of 30 mg P 〈 dm -3 soil. Seedlings in unfer- tilized soil with 4 mg P 〈 dm -3 soil were excessively dependent on the mycorrhizal associa- tion. In soil with 11 mg P 〈 dm -3 soil, seedlings were marginally to moderately dependent, depending upon the AMF species used. All inoculated seedlings, without considering soil sterilization, were marginally dependent in soil with 30 mg P 〈 dm -3 soil. In sterilized soil, independently of P, they were moderately dependent. However, in the same soil, with 30 mg P 〈 dm -3 soil, the seedlings were marginally dependent. Discussion - conclusion. The relative mycorrhizal dependency (RMD) of the passion fruit cultivar used was influenced by the species of the inoculated AMF, soil sterilization and soil P level. Passion fruit obtained significant benefit from inoculation with AMF; thus, these fungi can be used to improve plant growth even without P fertilization. Brazil / Passiflora edulis / fertilizer application / phosphate fertilizers / phosphorus / vesicular arbuscular mycorrhizae / biomass