Arbuscular Mycorrhizal Fungi Colonization Promotes Changes in the Volatile Compounds and Enzymatic Activity of Lipoxygenase and Phenylalanine Ammonia Lyase in Piper nigrum L. 'Bragantina'

Arbuscular mycorrhizal fungi (AMF) have been used to promote numerous benefits to plants. In this study, we evaluated the symbiosis between AMF species (Rhizophagus clarus, Claroideoglomus etunicatum) and Piper nigrum L. 'Bragantina'. Volatile compounds, lipoxygenase (LOX) and phenylalanine ammonia-lyase (PAL) activities, and total phenolic content were monitored from 1 to 60 days post-inoculation (dpi). Hyphae, arbuscles, and vesicles were observed during the root colonization. In the leaves, AMF induced an increase of sesquiterpene hydrocarbons (54.0%-79.0%) and a decrease of oxygenated sesquiterpenes (41.3%-14.5%) at 7 dpi and 60 dpi (41.8%-21.5%), respectively. Cubenol, the main volatile compound of leaves, showed a significant decrease at 7 dpi (21.5%-0.28%) and 45 dpi (20.4%-18.42%). beta-caryophyllene, the major volatile compound of the roots, displayed a significant reduction at 45 dpi (30.0%-20.0%). LOX increased in the roots at 21, 30, and 60 dpi. PAL was higher in leaves during all periods, except at 60 dpi, and increased at 21 and 45 dpi in the roots. The total phenolic content showed a significant increase only in the roots at 30 dpi. The results suggested that AMF provided changes in the secondary metabolism of P. nigrum, inducing its resistance.