Factors affecting microspore embryogenesis in Petunia
Microspore culture provides a convenient system for haploid production in breeding programmes. This technique has been used successfully in many plant species, including wheat, barley, and tobacco, but little information has been reported about microspore culture in Petunia. Therefore, in this study, important factors affecting microspore culture were studied such as genotype, stress treatments, culture media, microspore density and the most responsive developmental stage in microspores. Isolated microspores from three Petunia cultivars ('Purple Wave', 'Star Wave' and clone #18) were cultured in two media: B medium with 5.47% (w/v) mannitol and MN medium with 2% sucrose and 2% glucose (w/v). Globular embryos were produce successfully in all Petunia genotypes in both media without significant differences. Three stress treatments (cold, 5±1°C; heat, 33±1°C; and cold followed by heat) were applied to the anthers and microspores for 7 days. The results demonstrated the necessity of stress treatment, especially heat stress, to induce globular embryos in Petunia. Heat stress for 3-7 days stimulated production of microspore-derived embryos. The importance of microspore density for embryogenesis could be also proved. Of three culture densities (X=8×104, 2X=16×104 and 4X=32×104), 2X=16×104 microspores mL-1 was optimal for embryogenesis in Petunia 'Purple Wave'. By distribution of flower buds of Petunia 'Purple Wave' into three groups (4-6, 7-10 and 11-14 mm bud length) and DAPI staining to investigate the developmental stage of microspores, the optimal developmental stage of microspores could be determined. Flower buds 7-10 mm long containing microspores at late uninucleate stage were the most responsive.
Chaar, M., Pinker, I. and Böhme, M. (2016). Factors affecting microspore embryogenesis in Petunia. Acta Hortic. 1127, 163-170
microspore embryogenesis, globular embryo, microspore stage, DAPI, heat stress, B medium