Mycorrhizal colonization and spore density in Citrus sinensis-weed interaction

Abstract Arbuscular mycorrhizal fungi (AMF) are microorganisms that establish symbiotic associations with the roots of most crops, enhancing water and nutrient uptake, thus improving growth and yield. However, limited attention has been given to the interactions between crops, weeds and AMF. This study investigates AMF root colonization and spore density in Citrus sinensis (L.) cv. Thompson Navel and dominant weed species within a Mediterranean orchard in El-Tarf Province, Algeria. Different sections of the orchard were characterized by varying dominant weed species: Oxalis pes-caprae in the western area (S1), Medicago polymorpha in the center (S2), Poa trivialis in the east (S3), and minimal weed presence at the edge (S4). Root colonization levels indicated low mycorrhizal intensity (M%) in both C. sinensis and dominant weeds, ranging from 3.72% to 15%. Spore density in S1, S2, and S3 varied between 178 and 432 spores per 50 g of soil, whereas S4 had a significantly higher density of 897 spores (a 404% increase in comparison to S1). C. sinensis and co-occurring weeds had low mycorrhizal colonization, while the highest spore density was observed in the section without dominating weeds, highlighting the influence of weed identity on AMF dynamics and the detrimental effects of conventional agricultural practices.