Callus Initiation, Plant Regeneration, and Evidence of Somatic Embryogenesis in Red Fescue¹

Abstract

The effects of auxin type and concentration on callus growth of two cultivars of red fescue ( Festuca rubra L. var commutata Gaud. ‘Jamestown’ and F. rubra L. var trichophylla Gaud. ‘Dawson’) were evaluated and the potential for plant regeneration over extended culture periods was determined. Mature caryopses of each cultivar were dehusked, surface sterilized, and cultured for 8 weeks on one‐half strength Murashigea nd Skoog (M + S) mediumco ntaining either 2,4‐D [(2,4‐dichlorophenoxy) acetic acid], 2,4,5‐T [(2,4,5‐trichlorophenoxya)c etic acid], or NAA (a naphthaleneacetic acid) at concentrations of 10, 20, 30, or 40μM. Maximum callus induction and growth were promoted by 20 μM 2,4‐D for both Jamestown and Dawson with 2,4,5‐T being as effective as 2,4‐D for Dawson. All concentrations of NAA tested were ineffective for both cultivars. Calli of both cultivars were initiated with 20 μM 2,4‐D and were subcultured at 8‐week intervals for 24 weeks. At both 16 and 24 weeks calli were transferred to regeneration medium consisting of one‐half strength M + S media with 0.1 mg/L BA [6‐(benzylamino purine]. Plant regeneration was extremely high at both 16 and 24 weeks from Dawson callus compared to Jamestown. The majority of Dawson calli were shown to be embryogenic and were white to yellow and compact compared to the translucent, friable nonembryogenic Jamestown callus. The increased frequency and duration for plant regeneration from Dawsonca llus was attributed to somatic embryogenesis associated with embryogenic callus.