Given the importance of borage (Borago officinalis L.) as a medicinal herb, androgenic studies are necessary in order to speed up the breeding programs of this plant species. In this work, we evaluated the effect of silver nitrate, activated charcoal, ascorbic acid, and polyvinylpyrrolidone (PVP), previously described as antibrowning agents and promoters of androgenesis. Adding silver nitrate at a concentration of 5 mg L–1 significantly enhanced the androgenic responses of cultured anthers up to ~2-fold for total calli production (53.33%) and up to ~2.5-fold for embryonic calli and embryo formation (30% and 0.3 embryos/anther, respectively) compared to control culture medium. Culture media containing 5 and 10 mg L–1 silver nitrate and 2 mg L–1 PVP significantly reduced the callus browning and led to increased callus viability in borage cultured anthers. We also evaluated the effect of various combinations of picloram with 2-isopentyl adenine and 2,4-dichlorophenoxyacetic acid (2,4-D) as growth regulators in he standard protocol. Significantly better results were obtained by adding 2 mg L–1 picloram in combination with 2 mg L–1 2,4-D in culture medium. This medium produced the highest frequencies of callogenesis (48.33%), embryogenic calli (20%), and embryo formation (0.2 embryos/anther) compared to control and other growth regulator combinations.
