[Show abstract][Hide abstract] ABSTRACT: Protocols were developed for the generation of haploid and doubled haploid plants from isolated microspores 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 4 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 2 and 6 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.
Plant Cell Tissue and Organ Culture 03/2012; 112(3). DOI:10.1007/s11240-012-0235-5 · 2.61 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: An F2 population derived from two carrot inbred lines, P50006 and HCM A.C. with high carotene accumulation, was developed and used to map and analyze quantitative trait locus (QTL) associated with the accumulation of alpha and beta-carotene, total carotene and lycopene. Broad-sense heritabilities of these traits were 0.75, 0.50, 0.31, and 0.93, respectively. A genetic map with 91 SRAP (Sequence-related amplified polymorphism) markers was developed, which spanned 502.9 cM in 9 linkage groups with a mean marker interval of 5.5 cM. Mixed-model-based composite interval mapping was performed to analyze QTL and epistasis effects. One major QTL each for beta-carotene, total carotene and lycopene accumulation were detected which can explain 12.79%, 12.87%, and 14.61% of total phenotypic variations, respectively. Additive genetic variance was primarily responsible for genetic variability in all three major QTL. In addition, a pair of epistasis QTL for beta-carotene and lycopene accumulation was detected, which were able to explain 15.1% and 6.5% of total phenotypic variation, respectively. The dominant x additive and dominant x dominant interaction variance were primary epistasis effect for beta-carotene and lycopene. These SRAP markers linked to QTL could be used in selection or QTL pyramiding for high carotene and lycopene content in carrot breeding.