A protocol for the generation of Arachis hypogaea composite plants: A valuable tool for the functional study of mycorrhizal symbiosis

PREMISE: Agrobacterium rhizogenes–induced hairy root systems are one of the most preferred and versatile systems for the functional characterization of genes. The use of hairy root systems is a rapid and convenient alternative for studying root biology, biotic and abiotic stresses, and root symbiosis in in vitro recalcitrant legume species such as Arachis hypogaea. METHODS AND RESULTS: We present a rapid, simplified method for the generation of composite A. hypogaea plants with transgenic hairy roots. We demonstrate a technique of hairy root induction mediated by A. rhizogenes from young A. hypogaea shoots. The efficacy of the system for producing transgenic roots is demonstrated using an enhanced green fluorescent protein (eGFP) expression vector. Furthermore, the application of the system for studying root branching is shown using the auxin‐responsive marker DR5 promoter fused to β‐glucuronidase (GUS). Finally, the success of the hairy root system for root symbiotic studies is illustrated by inoculating hairy roots with arbuscular mycorrhizal fungi. CONCLUSIONS: In this study, we have developed a rapid, efficient, and cost‐effective composite plant protocol for A. hypogaea that is particularly effective for root‐related studies and for the validation of candidate genes in A. hypogaea during mycorrhizal symbiosis.