| Carrot (Daucus carota var. sativus) is an important vegetable and it is cultivated worldwide because of its nutrition (provitamin A) and use as a fresh or processing vegetable. In the current ten years the production area of China has increased four times and about 42% of the total world. In the paper, carrot breeding progress and development of carrot production in China were discribed, and germplasm resources, chromosomes, microspore culture and emasculation method were studied.1. Germplasm resourcesIn order to establish a core collection of Chinese traditional carrot germplasm, a total of 340 accessions was evaluated for 4 quantitative and 9 qualitative traits and the data were submitted for cluster analyses. Under the suitable threshold value, the accessions that were closer to the value were selected as candidates to form core collection. Three sampling proportions of 10%, 15% and 20% were used to establish core collection. Thirteen traits were compared between three core collections and entire collection in order to test the validity of primary core collections. The results showed that the means ofβ-carotene content, dry matter content and vitamin C content were significant between the primary core collections and the entire collection, while the ratios of phenotype retained of 4 quantitative traits were high. Variances of phenotype frequency of 9 qualitative traits were not significant between the primary core collections and the entire collection while the ratios of phenotype retained were 100%. With sampling proportion reduced, the number of regions that core collection distributed decreased. Eight regions were reduced and germplasm proportion from the main regions was reduced from 50% to 35% between 10% core collection and the entire. Fifteen to twenty percent could be regarded as the optimal proportion for establishing Chinese traditional carrot germplasm core collection.2. ChromosomesWell-spread and clear metaphase chromosomes of carrot were obtained, after the pretreatment of root tips in vivo with two chemicals, cycloheximide (CHX) and p-dichlorobenzene (pDB). The results from the karyotype analysis indicated that there were a pair of satellite chromosomes and the average length of chromosomes was 2.34μm. 22.2% of the chromosomes with arm ratio over 2, and the ratio of the longest chromosome to the shortest one is 2.24:1, thus it belongs to 2B type, and the karyotype formula is 2n =2x =18 =8m (2SAT)+10m. There was no abnormal behavior observed in meiotic chromosomes in carrot. It has simultaneous cytokinesis. There are nine bivalents (9II) at metaphase I, indicating it is a typical diploid species.3. Haploid cultureDifferent genotype varieties were used to study the anther and microspore culture in vitro. Calli regenerated from anters in 7 materials, and those of HCM, 36 and 9 were embryonic but others were non-embryonic calli. These calli were cultured on the differentiation media for a week and then growed into the plantlets. In the isolated microspore culture, part of microspores were swelled and few could develop into tetrads and died after 1 week..4. Emasculation methodThe effect of emasculation with adhesive tape in carrot was investigated. The results showed that the ratio of seed of the crosses was higher than that of selfing. 7262B×HCM, 62-1×HCM, 296-8×F8-9-3 and 296-8×HCM were 53.8%, 53.4%, 83.5% and 67.6% respectively while the selfing lines were below 10%. The shoot growth of 296-8×F8-9-3, 62-1×HCM, and 7262B×HCM were stronger than the pollinatior lines. The leaf dissection of 7262B×HCM and 296-8×F8-9-3 showed paternal transmission, and root skin colour of 7262B×HCM showed maternal transmission. The emasculation method is effective and rapid for carrot, and the heredit of important characters could be further studied.
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