Effects of hygromycin on cotton cultures and its application in Agrobacterium-mediated cotton transformation

We have evaluated the effects of the antibiotic hygromycin B on cotton (Gossypium hirsutum L.) callus induction, callus proliferation, and seed germination. Nontransgenic cotyledon and hypocotyl showed obvious variance in tolerance to hygromycin. Cotyledons were more sensitive to hygromycin than hypocotyls. Hygromycin at 7.5 and 20 mg 1(-1) completely inhibited callus initiation from cotyledon and hypocotyl explants, respectively. Non-transformed calli did not grow on media supplemented with 10 mg 1(-1) hygromycin and were killed at 15 mg 1(-1). In seed germination assay, the presence of 20 mg 1(-1) hygromycin significantly suppressed shoot and root elongation of seedlings. This hygromycin concentration was applied to select regenerated transgenic plantlets and their progenies. Based on these results, we developed an efficient hygromycin selection protocol for Agrobacterium-mediated cotton transformation and regeneration.