EFFECTS OF BRASSINOSTEROIDS ON MICROSPORE EMBRYOGENESIS IN BRASSICA SPECIES

Experiments were conducted to determine the effects of brassinosteroids on microspore embryogenesis in Brassica species. Two compounds, 24-epibrassinolide (EBR) and brassinolide (BL), were evaluated. An increase in embryogenesis was observed in all Brassica napus lines evaluated, including Topas 4079 and several recalcitrant cultivars: Garrison, Westar, and Allons. Microspore embryogenesis, calculated as the number of embryos at 21 d of culture, was increased in the recalcitrant cultivars up to 12 times that of the control. An increase in microspore embryogenesis was also observed for B. juncea when EBR or BL was added to the culture medium. In contrast, no significant increase in embryogenesis was observed for several other Brassica species evaluated (i.e. B. carinata, B. nigra, and B. rapa). The addition of brassinosteroids to the induction media did not affect the subsequent conversion of the embryos to plantlets, but did appear to influence chromosome doubling.