Effects of mefluidide and dicamba on in vitro growth and embryogenesis ofDactylis glomerata (orchard grass)

The effects of N-(2,4-dimethyl-5-(((trifluoromethyl)sulfonyl)amino)phenyl)acetamide (mefluidide) and 3,6-dichloro-o-anisic acid (dicamba) on in vitro growth and somatic embryogenesis ofDactylis glomerata L. (orchard grass) were studied using suspension cultures and explanted leaf bases. All experiments employed modified Schenk and Hildebrandt medium amended with concentrations of dicamba ranging from 15 to 120 μM (SH-15 to SH-120) and of mefluidide ranging from 1 to 100 μM. SH medium without either growth regulator was used for embryo germination. Embyro production in suspension cultures with SH-30 medium plus 3 g/L casein hydrolysate was significantly reduced by 1 μM mefluidide. Only 15% of these embryos germinated and produced plants compared to 84% from controls. Growth, as measured by dry weight, was significantly reduced by 50 or 100 μM mefluidide. The number of embryos formed on leaf sections was significantly reduced by 20 or 25 μM mefluidide. Embryos that formed with 10 μM or more mefluidide were callused on both SH-15 and SH-30 media. Shoot formation was inhibited from individual embryos and embryo/callus masses that developed on either SH-15 or SH-30 medium containing 5 μM or more mefluidide. Radicle emergence was significantly reduced with 10 μM mefluidide regardless of 15 or 30 μM dicamba. Histological examination revealed that mefluidide inhibited both shoot and root meristem development with shoot development being the more sensitive. Inhibition of both was independent of dicamba concentrations. Shoot formation was also reduced from embryos that had developed on SH-30 medium without mefluidide when transferred to medium containing mefluidide without dicamba.