Zhenqing Zhao

Characterization of the Appearance, Health-Promoting Compounds, and Antioxidant Capacity of the Florets of the Loose-Curd Cauliflower

Four loose-curd cauliflower varieties, and one common cauliflower cultivar, were studied to investigate the appearance, antioxidant capacity, and levels of ascorbic acid, chlorophylls, carotenoids and glucosinolates in the florets. The loose-curd cauliflower was typically characterized by a loose curd and long florets with green pedicels and a yellow surface. The levels of total glucosinolates, sinigrin, and neoglucobrassicin were lower in the loose-curd cauliflower varieties than in the common cauliflower. The amount of glucoiberin, major aliphatic glucosinolate, present in loose-curd cauliflower varieties, was 147 to 241 nmol/g dry weight (average: 147 nmol/g dry weight). In contrast, the common cauliflower contained a much higher amount of sinigrin (249 nmol/g dry weight) than glucoiberin (56 nmol/g dry weight). All cauliflower varieties contained minor amounts of progoitrin and neoglucobrassicin. Furthermore, the loose-curd cauliflower varieties exhibited comparably higher levels of ascorbic acid, chlorophylls, and carotenoids, than total phenolics. The ferric reducing antioxidant power values in the loose-curd varieties ranged from 92 ± 7 to 107 ± 8 μmol Fe2+/g dry weight, which were also higher than that in the common cauliflower. The results indicated that the loose-curd cauliflower can provide higher levels of health-promoting compounds than the common cauliflower.

Protoplast isolation and plant regeneration of different doubled haploid lines of cauliflower (Brassica oleracea var. botrytis)

Protoplasts were isolated from hypocotyls of 5-day-old seedlings of five doubled-haploid (DH) lines of cauliflower after enzymatic digestion in 0.1% macerozyme R-10 and 1.0% cellulose R-10. Shoot regeneration was achieved in four of the five DH lines. Protoplast yield and frequency of cell division and shoot regeneration varied among experiments and DH lines. Sequence-related amplified polymorphism (SRAP) analysis on all the regenerated plants of each DH line indicated that their genetic compositions were homologous with their mother plants, but few regenerated plants of DH lines no. 3 and 5 were detected with changes in ploidy levels.

Genome-Wide Single-Nucleotide Polymorphisms Discovery and High-Density Genetic Map Construction in Cauliflower Using Specific-Locus Amplified Fragment Sequencing

Molecular markers and genetic maps play an important role in plant genomics and breeding studies. Cauliflower is an important and distinctive vegetable; however, very few molecular resources have been reported for this species. In this study, a novel, specific-locus amplified fragment (SLAF) sequencing strategy was employed for large-scale single nucleotide polymorphism (SNP) discovery and high-density genetic map construction in a double-haploid, segregating population of cauliflower. A total of 12.47 Gb raw data containing 77.92 M pair-end reads were obtained after processing and 6815 polymorphic SLAFs between the two parents were detected. The average sequencing depths reached 52.66-fold for the female parent and 49.35-fold for the male parent. Subsequently, these polymorphic SLAFs were used to genotype the population and further filtered based on several criteria to construct a genetic linkage map of cauliflower. Finally, 1776 high-quality SLAF markers, including 2741 SNPs, constituted the linkage map with average data integrity of 95.68%. The final map spanned a total genetic length of 890.01 cM with an average marker interval of 0.50 cM, and covered 364.9 Mb of the reference genome. The markers and genetic map developed in this study could provide an important foundation not only for comparative genomics studies within Brassica oleracea species but also for quantitative trait loci identification and molecular breeding of cauliflower.

An efficient shoot regeneration system and Agrobacterium-mediated transformation with codA gene in a doubled haploid line of broccoli

Abstract: Broccoli is an important vegetable crop belonging to the genus of Brassica. However, it is often affected by biotic and abiotic stresses that result in large losses in yield and quality. Genetic manipulation has opened the opportunity for germplasm improvement of broccoli. In this study, an efficient shoot regeneration and Agrobacterium-mediated transformation system was established. The optimum medium for shoot induction was selected for three types of explant including hypocotyl, petiole, and peduncle, and up to 90% regeneration frequency was obtained. The transformation procedure was developed with the EHA105 strain, harboring the PUC19 vector, along with the target gene of codA and a hygromycin-resistance gene. Several factors were optimized, including hygromycin concentration for selection and the Agrobacterium density yielding the highest transformation frequency. Among the three types of explants, peduncle explants showed the highest response to this procedure, and the highest frequency of transformation (3.4%) was obtained depending on the analysis of polymerase chain reaction and Southern blot. In conclusion, the present study introduced a reliable system for plant regeneration and genetic transformation with three types of explants for a DH line of broccoli, and peduncle explant resulted in the highest transformation frequency.