Conversion of oat (Avena sativa L.) haploid embryos into plants in relation to embryo developmental stage and regeneration media.

Obtaining oat DH lines is only effective via wide crossing with maize. Seven hundred haploid embryos from 21 single F1 progeny obtained from wide crosses with maize were isolated, divided into four groups according to their size (<0.5 mm, 0.5-0.9 mm, 1.0-1.4 mm, and ≥1.5 mm), and transferred into 190-2 regeneration medium with different growth regulators: 0.5 mg L-1 kinetin (KIN) and 0.5 mg L-1 1-naphthaleneacetic acid (NAA); 1 mg L-1 zeatin (ZEA) and 0.5 mg L-1 NAA; or 1 mg L-1 dicamba (DIC), 1 mg L-1 picloram (PIC), and 0.5 mg L-1 kinetin (KIN). Among all isolated embryos, approximately 46.1% were between 1.0-1.4 mm, while the smallest group of embryos (7.1%) were those <0.5 mm. The ability of haploid embryos to germinate varied depending on oat genotypes and the size of embryos. Haploid embryos <0.5 mm were globular and did not germinate, whereas embryos ≥1.5 mm had clearly visible coleoptiles, radicles, and scutella, and were able to germinate. Germination of oat haploid embryos varied depending on growth regulators in the regeneration medium. Most haploid embryos germinated on medium with 0.5 mg L-1 NAA and 0.5 mg L-1 KIN, while the fewest germinated on medium with 1 mg L-1 DIC, 1 mg L-1 PIC, and 0.5 mg L-1 KIN. One hundred thirty germinated haploid embryos converted into haploid plants. Fifty oat DH lines were obtained after colchicine treatment.