Microspore embryogenesis and plant regeneration in Brussels sprouts (Brassica oleracea L. var. gemmifera)

Abstract

As a tool in genetic engineering, isolated microspore cultures have the remarkable quality to produce doubled haploids for plant breeding and gene mapping. Protocols were developed for the induction of microspore-derived embryos and generation of doubled haploid plants from isolated microspores of Brussels sprouts. A cytological analysis showed that two modes of Brussels sprouts microspore embryogenesis exist: a direct route via embryos which was the major developmental pathway, and an indirect route via calli. Cold pretreatment (4°C) and aminoethoxyvinylglycine addition were tested to determine whether and how they could improve embryogenesis. Cold pretreatment improved the viability of microspores, and stimulated to produce embryos directly. Similarly, aminoethoxyvinylglycine had a positive effect on the number of embryos produced via improving multinucleate structures to further develop. The combination of cold pretreatment for 24h and 1μM aminoethoxyvinylglycine addition significantly enhanced microspore embryogenesis efficiency, especially with low responsive genotype ‘1076’ for which it was increased by about 82-fold. Subsequently, the use of solid B5 medium with 1% agarose and 2% sucrose (w/v) achieved an efficient rate of plant regeneration, and more than 67% of regenerated plants were spontaneous diploids.