36th International Carrot Conference Abstract

Isolated Microspore Culture in Carrot

Fei-Yun Zhuang, Cheng-Gang Ou, Jin-Rong Li, Zhi-Wei Zhao

Key Laboratory of Horticultural Crop Biology and Germplasm Innovation, Ministry of Agriculture, Institute of Vegetables and Flowers, Chinese Academy of Agricultural Science

NO. 12 Nanda Street, Zhongguan Cun, Haidian District, Beijing 100081, China

E-mail: fyzhuang2008@yahoo.com.cn

Carrot (Daucus carota L.) is an out-crossing biennial species, and one of the most economically important vegetable crops worldwide. Its flowering is initiated after a vernalization period of eight to 10 weeks and the crop is typically bred in an annual cycle. Selection and production of inbred lines is time consuming and difficult to achieve. A doubled haploid (DH) line is valuable for crop breeding programs because traits are fixed without multiple self-pollinating generations. Apiaceae species are considered to be recalcitrant to DH technologies, although carrot is a model plant for tissue culture and limited progress on anther culture. Compared with anther culture, the procedure of isolated microspore culture (IMC) is simpler and more efficient. Protocols were developed for the generation of haploid and doubled haploid plants from IMC of carrot (Daucus carota L.). Forty-seven carrot accessions, including six inbred lines, 11 cultivars, 20 F₁s, two BC₁F₁s, four F₂s, one F₃, and three F₄s, were screened to evaluate the genotype influence on isolated microspore embryogenesis over four years. Twenty-eight accessions responded by producing embryos and/or calli. A cytological analysis showed that two modes of carrot microspore embryogenesis exist: an indirect route via calli (C mode), and a direct route via embryos (E mode). Eleven accessions were in the C mode, and 17 were in both modes. The highest production rates were in 10Y25 (a European Nantes cultivar) with 27 calli and 307 embryos, and 100Q6 (a semi-Nantes F₁ hybrid) with 176 calli and 114 embryos. The time period to produce embryos or calli differed significantly between two and six months. Cold and heat pretreatment generally had a negative impact on the induction of microspore embryogenesis, but a short pretreatment showed a positive influence on some accessions. Twenty-eight lines regenerated plants from the primary individual embryos or calli of three accessions were established to analyze the ploidy level. The percentage of spontaneous diploidization showed very wide differences among the accessions and lines. Differences in leaf color intensity, leaf size, and leaf dissection were found among haploid, doubled haploid, and triploid plants. Most of the plants appeared low fertility with brown anthers and even petaloid type. About 30 plants produced the seeds for further assessment. This suggested that isolated microspore culture would be effectively ingrate into conventional carrot breeding program, but great efforts of research need to aim at developing and optimizing protocols to obtain well developed embryos and high plant regeneration rates, and large plantlets population for seeds and assessment.

Key words: Microspore culture · Haploid · Doubled haploid · Cytology · Genotype · Fertility · Carrot · Daucus carota L

Last updated Thursday, 25-Jul-2013 11:53:07 CDT