Allelopathy of the essential oil of Fortunella margarita (Lour.) Swingle) in the germination on Helianthus annuus L. and Hordeum vulgare L.

Abstract

Fortunella margarita known as ‘Kin-Kan or kumquat orange’ is a citrus species cultivated in South America with excellent adaptation to different climates, especially tropical. The fruits of F. margarita have a spectacular essential oil content. This study aimed to evaluate the allelopathic action of essential oil from ripe fruits of F. margarita in different concentrations on two large crops, sunflower (Helianthus annuus) and barley (Hordeum vulgare) in vitro. Ripe fruits of F. margarita were collected from an orchard in Rio Verde, Goiás, Brazil in January 2024. The skin of the fruits was removed and crushed to obtain the essential oil by Clevenger. The essential oil content obtained was expressed as a percentage (%). For the chemical profile, gas chromatography with sequential mass spectrometry (GC-MS) was used. For the allelopathic assay, varying concentrations of essential oil were produced. The allelopathic test was carried out in acrylic germination boxes and kept in a D.B.O. vegetation chamber. The results were expressed as percentage of germination µL mL-1. The radicle length was determined using a digital caliper and expressed in centimeters (cm). Seven major volatile compounds were obtained (D-Limonene 22%, β-Phellandrene 12%, β-Pinene 11%, Germacrene D 9%, Bicyclosexquiphellandrene 8%, Trans-Arbuscolene and α-Guaiene both with 5%). The essential oil demonstrated strong allelopathic activity on sunflower germination rates, especially for concentrations greater than 12.5-100 µL mL-1, between 54.40 and 12.80%. Barley seeds demonstrated resistance and a rate greater than 50% at the highest concentration (100 µL mL-1). Radicle length also showed a significant difference (P < 0.05) in all essential oil concentrations. Again, sunflower was strongly affected, with average primary roots between 0.98 and 0.11 cm and between 2.77 and 0.11 cm for barley. The essential oil from the ripe fruits of Fortunella margarita has an allelopathic action on germination and a toxic effect on the development of primary roots in sunflower and barley seeds.