EMBRYOGENIC CALLUS INDUCTION AND PLANT REGENERATION MEDIA FOR BENTGRASSES AND ANNUAL BLUEGRASS

Embryogenic callus induction and plant regeneration systems have long been established for creeping bentgrass (Agrostis palustris Huds.), but little research has been reported on optimal medium for embryogenic callus induction and plant regeneration in velvet bentgrass (Agrostis canina L.), colonial bentgrass (Agrostis capillaries L.), and annual bluegrass (Poa annua L.). The present study compared 14 callus induction media and eight regeneration media for their efficacies on embryogenic callus induction and plant regeneration in these four species. The embryogenic callus initiation media contained the Murashige and Skoog inorganic salts and vitamins supplemented with 2,4-dichlorophenoxyacetic acid or 3,6-dichloro-anisic acid and 6-benzyladenine. L-Proline or casein hydrolyzate was included in some media to stimulate embryogenic callus formation and plant regeneration. The frequencies of embryogenic callus formation ranged from 0% to 38% and exhibited medium differences within each of the four species. Callus induction media, plant regeneration media, and genotypes affected plant regeneration rates, which varied between 0% and 100%. The embryogenic callus induced on Murashige and Skoog medium supplemented with 500 mg l-1 casein hydrolyzate, 6.63 mg l-1 (30 μM) 3,6-dichloro-anisic acid and 0.5—2.0 mg l-1 (2—9 μM) 6-benzyladenine had much higher regeneration rates than those formed on other callus induction media. Embryogenic callus of annual bluegrass had higher regeneration rates than those of bentgrass species. MSA2D, a media containing 2 mg l-1 (8 μM) 2,4-dichlorophenoxyacetic acid, 100 mg l-1 myo-inositol, and 150 mg l-1 asparagine, was effective in promoting embryogenic callus formation in creeping bentgrass but not in colonial and velvet bentgrasses and annual bluegrass.