|FU, XUELIN - South China Agricultural University|
Submitted to: Helia
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/15/2017
Publication Date: 6/27/2017
Citation: Fu, X., Qi, L., Hulke, B., Seiler, G., Jan, C. 2017. Somatic embryogenesis from corolla tubes of interspecific amphiploids between cultivated sunflower (Helianthus annuus L.) and its wild species. Helia. 40(66):1-19.
Interpretive Summary: Sunflower (Helianthus annuus L.) is one of the important oil seed crops supplying healthy oil high in nutritional value for human consumption. Wild sunflower species are known to possess an abundance of unique genes for sunflower improvement. However, transfer of wild species genes into cultivated sunflower is restricted by cross incompatibility and hybrid sterility. Alternative conservation and propagation of the interspecific F1 plants and amphiploids through tissue culture has the potential of providing a large number of plants for breeding programs. Sunflower plants parts including shoot apices, hypocotyls, cotyledons, leaves, protoplasts, and mature embryos have been used to induce calli or somatic embryos with limited success. In this study, using flower corolla tubes of chromosomally doubled interspecific hybrids, protocols of direct embryo formation has been developed, and we obtained high frequencies of secondary somatic embryos and regenerated plants. This provides means of producing multiple hybrid plants for continuing crosses to cultivated sunflower for gene transfer as well as for studies on somaclonal variation, plant differentiation, and micro-proliferation. Results of this study will contribute to extend the explant types and embryo induction methods in sunflower. Continued validation and optimization of this system in a larger number of sunflower genotypes should be carried out in the future.
Technical 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.