Callus Induction and Plantlet Formation from Mature Embryo Explants of Kentucky Bluegrass1

Primary objectives of this research were to demonstrate callus induction and plantlet regeneration from mature embryo explants of Kentucky bluegrass ( Poa pratensis L.) and to determine if the mode of plantlet regeneration was by organogenesis or embryogenesis. Mature embryos of six cultivars or strains were plated on a modified Schenk and Hildebrandt agar medium in a series of three experiments. Results of the first experiment, testing three synthetic auxins at varying concentrations, showed that dicamba (3,6‐dichloro‐o‐anisic acid) at 20 μM and picloram (4‐amino‐3,5,6‐trichloropicolinic acid) at 60 μM produced the best callus growth and most germination suppression. Results of the second experiment comparing plant regeneration of cultivars varying in their percent of apomictic reproduction indicated variation in callusing and plant regeneration among entries, low frequencies of plantlet formation and no relationship between apomixis and plant regeneration. Chromosome counts showed no definitive differences between cultivar reference and regenerated plants. Results of the third experiment comparing culture temperature (25 vs. 15°C) both with and without a 4°C cold treatment for 7 days showed 15°C with a cold treatment increased plant regeneration in ‘Ram I.’ A histological examination of calli in the latter two experiments showed the mode of plant regeneration to be organogenesis.