Xuelin Fu, Lili Qi, Brent Hulke, Gerald Seiler, Chao-Chien Jan
Abstract: Somatic embryogenesis in vitro provides an efficient means of plant multiplication, facilitating sunflower improvement and germplasm innovation. In the present study, using interspecific amphiploids (2n=4x=68) between cultivated sunflower and wild perennial Helianthus species as explant donors, somatic embryos were induced directly from the surface of corolla tubes at the late uninucleate or binucleate microspore development stage. Primary somatic embryos (PSEs) were obtained in amphiploids G08/2280 (H. pumilus×P21) and G08/2260 (NMSHA89×H. maximiliani). The PSE induction frequency of G08/2280 on synthesized Medium A and B was 30.27 % and 42.42 %, respectively, while that of G08/2260 was 5.89 % and 12.16 %, respectively. The difference of PSE induction frequency was significant between G08/2280 and G08/2260 (P=0.0058), but was non-significant between induction Medium A and B (P=0.1997). Secondary somatic embryos (SSEs) were rapidly produced from PSEs on subculture Medium 1 with the induction frequency of 100 %. The mean number of SSEs produced from each PSE was 19.2 and 12.2 in G08/2280 and G08/2260 within 30 d of subculture, respectively. Mature SSEs were gradually converted into young shoots on hormone-free subculture Medium 2, with the mean number of small green shoots produced from each PSE of 22.0 and 18.7 in G08/2280 and G08/2260, respectively. Through the additional process of rooting for some shoots without roots on half-strength of MS medium adding 0.25–0.5 mg/l NAA, 0.5 mg–1.0/l IBA, SE-derived shoots without roots gained about 40 % rooting frequency. Regenerated plants acclimated successfully and displayed similar morphological and chromosome number to the amphiploid donors.
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