Arbuscular mycorrhizae maintain lemongrass citral levels and mitigate resistance despite root lesion nematode infection

Abstract

Cymbopogon citratus (lemongrass) is an essential oil-producing plant with commercially important pharmacological properties. The species is susceptible to plant-parasitic nematodes, which should preferably be managed by environmentally friendly methods, such as biological control. This study aimed to investigate the effectiveness of arbuscular mycorrhizal fungi (AMF) in the control of Pratylenchus brachyurus on C. citratus and assess interaction effects of these microorganisms on vegetative development, essential oil composition, and defense-related enzyme activity. Plants were inoculated with one of two AMF species (Rhizophagus clarus or Claroideoglomus etunicatum) alone or together with P. brachyurus. An uninoculated uninfected control was also included. At 90 days after inoculation, plants were harvested and evaluated for vegetative growth, nematode parameters, mycorrhizal spore count, root colonization, essential oil composition, and activation of defense-related proteins. Citral was the major component of C. citratus essential oil. AMF inoculation increased nematode population by 8.6 × compared with non-inoculation and did not improve plant growth compared with the control. Nevertheless, AMF efficiently colonized plant roots, maintained citral content at levels similar to those of nematode-free plants, and increased the activity of defense-related enzymes, such as peroxidase, β-1,3-glucanase, and polyphenol oxidase.