Improving microspore culture as a rapeseed breeding tool: the use of auxins and cytokinins in an induction medium

Abstract

The effect of naphthaleneacetic acid (NAA), an auxin, and N 6 -benzyladenine (BA), a cytokinin, on microspore embryogenesis in two F 1 (hybrids of rapeseed (Brassica napus L.) was investigated, using a two-factor, central-composite response surface design. Total embryo yields of both hybrids increased in a log-linear fashion with BA concentrations in the range 0.01–0.255 mg L −1 ; within this range, yields approximately doubled for every fivefold increase in BA concentration. NAA concentrations of 0.136–1.85 mg L −1 had no effect on embryo yields. Within the range of concentrations studied, neither growth substance had any effect on the proportion of cotyledonary embryos produced. When cotyledonary embryos were regenerated on B5 medium without hormones, no significant effects on either root development or shoot production attributable to the NAA–BA treatments could be detected. In general, higher embryo yields were associated with a slower rate of development, but a greater degree of morphological synchrony within individual cultures.