MORPHOGENETIC RESPONSE FROM ORCHARDGRASS PISTILS

Unpollinated orchardgrass (Dactylis glomerata L.) pistils from an embryogenic genotype were cultured on a Schenk and Hildebrandt (SH) basal medium supplemented with 3% sucrose and 30 μM 3,6-dichloro-o-anisic acid (dicamba) in the dark at 25°C. The experimental design was a randomized complete block with 6 treatments (1- to 6-week culture periods) and 3 blocks where each experimental unit consisted of 15 pistils. The morphogenetic response was followed at weekly intervals for 6 weeks by stereoscopic and scanning electron microscopy. Root-like protrusions emerged basipetally from approximately 15% of the pistils cultured for one week; however, no plants were regenerated from these structures. Ovary and style regions became swollen after 2 weeks, and embryoids emerged directly from these areas during the third week of culture. These embryoids acted as secondary expiants and initiated calli in 4-week-old cultures. During the fifth and sixth weeks, many embryoids were initiated from the newly formed calli. Three weeks after transfer of these cultures to dicamba-free medium, the embryogenic response was quantified by counting shoots. A significant F value (α = 0.05) for the treatment effects was followed by mean separation through orthogonal contrasts. This revealed no significant difference between the 3-and 4-week treatments.