Construction of a high-density genetic map and identification of loci controlling purple sepal trait of flower head in Brassica oleracea L. italica

Phyto-nutraceutical promise of Brassica vegetables in post-genomic era: a comprehensive review

MAIN CONCLUSION

Brassica vegetables are one of the possible solutions to tackle the emerging human diseases and malnutrition due to their rich content of phyto-nutraceutaical compounds. The genomics enabled tools have facilitated the elucidation of molecular regulation, mapping of genes/QTLs governing nutraceutical compounds, and development of nutrient-rich Brassica vegetables. The enriched food products or foods as whole termed as functional foods are intended to provide health benefits. The 2500 year old Hippocratic phrase 'let thy food be thy medicine and thy medicine be thy food' remained in anonymity due to lack of sufficient evidence. However, today, we are facing reappraisal of healthy nutritious functional foods in battling diseases. In this context, the Brassica vegetables represent the most extensively investigated class of functional foods. An optimal consumption of Brassica vegetables is associated with lowering the risks of several types of cancer, chronic diseases, cardiovascular disease, and help in autism. In the post-genomic era, the integration of genetic and neoteric omics tools like transcriptomics, metabolomics, and proteomics have illuminated the downstream genetic mechanisms governing functional food value of Brassica vegetables. In this review, we have summarized in brief the phyto-nutraceutical profile and their functionality in Brassica vegetables. This review also highlights the progress made in identification of candidate genes/QTLs for accumulation of bioactive compounds in Brassica vegetables. We summarize the molecular regulation of major phytochemicals and breeding triumphs in delivering multifunctional Brassica vegetables.

A SLAF-based high-density genetic map construction and genetic architecture of thermotolerant traits in maize (Zea mays L.)

The leaf scorching trait at flowering is a crucial thermosensitive phenotype in maize under high temperature stress (HS), yet the genetic basis of this trait remains poorly understood. In this study, we genotyped a 254 RIL-F2:8 population, derived from the leaf scorch-free parental inbred line Abe2 and the leaf scorching maternal inbred line B73, using the specific-locus amplified fragment sequencing (SLAF-seq) method. A total of 10,112 polymorphic SLAF markers were developed, and a high-density genetic map with a total length of 1,475.88 cM was constructed. The average sequencing depth of the parents was 55.23X, and that of the progeny was 12.53X. Then, we identified a total of 16 QTLs associated with thermotolerant traits at flowering, of which four QTLs of leaf scorching damage (LS) were distributed on chromosomes 1 (qLS1), 2 (qLS2.1, qLS2.2) and 3 (qLS3), which could explain 19.73% of phenotypic variation. Combining one qLS1 locus with QTL-seq results led to the identification of 6 candidate genes. Expression experiments and sequence variation indicated that Zm00001d033328, encoding N-acetyl-gamma-glutamyl-phosphate reductase, was the most likely candidate gene controlling thermotolerant traits at flowering. In summary, the high-density genetic map and genetic basis of thermotolerant traits lay a critical foundation for mapping other complex traits and identifying the genes associated with thermotolerant traits in maize.

Construction and Application of an F1-Derived Doubled-Haploid Population and High-Density Genetic Map for Ornamental Kale Breeding

Ornamental kale (Brassica oleracea var. acephala) is an attractive ornamental plant with a range of leaf colors and shapes. Breeding new varieties of ornamental kale has proven challenging due to its lengthy breeding cycle and the limited availability of genetic markers. In this study, a F1DH ornamental kale population comprising 300 DH lines was constructed using microspore culture. A high-density genetic map was developed by conducting whole-genome sequencing on 150 individuals from the F1DH population. The genetic map contained 1696 bin markers with 982,642 single-nucleotide polymorphisms (SNPs) spanning a total distance of 775.81 cM on all nine chromosomes with an average distance between markers of 0.46 cM. The ornamental kale genetic map contained substantially more SNP markers compared with published genetic maps for other B. oleracea crops. Furthermore, utilizing this high-density genetic map, we identified seven quantitative trait loci (QTLs) that significantly influence the leaf shape of ornamental kale. These findings are valuable for understanding the genetic basis of key agronomic traits in ornamental kale. The F1DH progenies provide an excellent resource for germplasm innovation and breeding new varieties of ornamental kale. Additionally, the high-density genetic map provides crucial insights for gene mapping and unraveling the molecular mechanisms behind important agronomic traits in ornamental kale.

Genome-wide identification and expression analysis of the bHLH gene family in cauliflower (Brassica oleracea L.)

Basic helix-loop-helix (bHLH) transcription factors (TFs) are one of the largest TF families in plant species, and they play important roles in plant growth, development and stress responses. The present study systematically identified members of the cauliflower (Brassica oleracea L.) bHLH gene family based on genomic data. Analysis of bHLH family gene numbers, evolution, collinearity, gene structures and motifs indicated that cauliflower contained 256 bHLH family genes distributed on 10 chromosomes. Most of these genes have been localized in the nucleus, and they were divided into 18 subgroups which have been relatively conserved during evolution. Promoter analysis showed that most cis-acting elements were related to MeJA and ABA. Expression analysis suggested that 14 bHLH genes may be involved in the transformation of cauliflower curd from white to purple. An expression analysis of these 14 genes in FQ136 material was performed using qRT-PCR, and 9 bHLH genes (BobHLH1, 14, 58, 61, 63, 84, 231, 239 and 243) showed significantly increased or decreased expression in cauliflower from white to purple, which suggests that these 9 genes play important roles in the accumulation of anthocyanins in cauliflower. The coexpression network of these 9 genes and anthocyanin synthesis-related key genes was analyzed using weighted gene coexpression network analysis (WGCNA). In conclusion, our observations suggested that the bHLH gene family plays an important role in the accumulation of anthocyanins in cauliflower and provide an important theoretical basis for further research on the functions of the bHLH gene family and the molecular mechanism of cauliflower coloration.

Supplementary Information

The online version contains supplementary material available at 10.1007/s12298-022-01238-9.

Development of Novel Markers and Creation of Non-Anthocyanin and Anthocyanin-Rich Broccoli (Brassica oleracea var. italica) Cultivars

In broccoli, anthocyanin pigments can be accumulated in the flower bud epidermis, resulting in a purple-green head. This study aimed to create non-anthocyanin green broccoli varieties and anthocyanin-rich purple broccoli varieties using new F3′H and Pur7.1-K1 molecular markers, respectively. The breeding program started with crosses of the recipient (superior variety and line) LF02 line with the donor line SN60 carrying the recessive allele f3′h and the donor line BT126 carrying the dominant allele Pur7.1. The F1 hybrids were confirmed with molecular markers and backcrossed with the recurrent parent LF02, followed by cycles of foreground and background selection at each stage. A total of 161 green plants with the f3′hf3′h genotype and 152 purple plants with the Pur7.1Pur7.1 genotype were selected from the BC3F2 line. Among these, 34 green plants and 28 purple plants demonstrated >85% background recovery. The identified plants were selfed to obtain 301 green and 416 purple BC3F3 plants for assessment of major agronomic traits. After these investigations, two green broccoli lines without anthocyanin and three anthocyanin-rich purple lines with the best yield/quality characteristics were obtained. The development of these lines might help provide basic materials and the theoretical basis for breeding commercial broccoli varieties.

Advances in Genetics and Molecular Breeding of Broccoli

Broccoli (Brassica oleracea L. var. italica) is one of the most important vegetable crops cultivated worldwide. The market demand for broccoli is still increasing due to its richness in vitamins, anthocyanins, mineral substances, fiber, secondary metabolites and other nutrients. The famous secondary metabolites, glucosinolates, sulforaphane and selenium have protective effects against cancer. Significant progress has been made in fine-mapping and cloning genes that are responsible for important traits; this progress provides a foundation for marker-assisted selection (MAS) in broccoli breeding. Genetic engineering by the well-developed Agrobacterium tumefaciens-mediated transformation in broccoli has contributed to the improvement of quality; postharvest life; glucosinolate and sulforaphane content; and resistance to insects, pathogens and abiotic stresses. Here, we review recent progress in the genetics and molecular breeding of broccoli. Future perspectives for improving broccoli are also briefly discussed.

Identification of Major Loci and Candidate Genes for Anthocyanin Biosynthesis in Broccoli Using QTL-Seq

Anthcyanins determine the colors of flowers, fruits, and purple vegetables and act as important health-promoting antioxidants. BT 126 represents a broccoli variety with a high content of anthocyanins (5.72 mg/g FW). Through QTL-seq bulk segregant analysis, the present study aimed to determine the quantitative trait loci (QTLs) involved in anthocyanin biosynthesis in the F2 population (n = 302), which was obtained by crossing BT 126 with a non-anthocyanin-containing SN 60. The whole-genome resequencing of purple (n = 30) and green (n = 30) bulk segregates detected ~1,117,709 single nucleotide polymorphisms (SNPs) in the B. oleracea genome. Two QTLs, tightly correlated with anthocyanin biosynthesis (p < 0.05), were detected on chromosomes 7 (BoPur7.1) and 9 (BoPur9.1). The subsequent high-resolution mapping of BoPur9.1 in the F2 population (n = 280) and F3 population (n = 580), with high-throughput genotyping of SNPs technology, narrowed the major anthocyanin biosynthesis QTL region to a physical distance of 73 kb, containing 14 genes. Among these genes, Bo9g174880, Bo9g174890, and Bo9g174900 showed high homology with AT5G07990 (gene encoding flavonoid 3′ hydroxylase), which was identified as a candidate gene for BoPur9.1. The expression of BoF3’H in BT 126 was significantly higher than that in SN60. Multiple biomarkers, related to these QTLs, represented potential targets of marker-assisted selection (MAS) foranthocyanin biosynthesis in broccoli. The present study provided genetic insights into the development of novel crop varieties with augmented health-promoting features and improved appearance.

Transcriptomic profiling of purple broccoli reveals light-induced anthocyanin biosynthetic signaling and structural genes

Purple Broccoli (Brassica oleracea L. var italica) attracts growing attention as a functional food. Its purple coloration is due to high anthocyanin amounts. Light represents a critical parameter affecting anthocyanins biosynthesis. In this study, 'Purple Broccoli', a light-responding pigmentation cultivar, was assessed for exploring the mechanism underlying light-induced anthocyanin biosynthesis by RNA-Seq. Cyanidin, delphinidin and malvidin derivatives were detected in broccoli head samples. Shading assays and RNA-seq analysis identified the flower head as more critical organ compared with leaves. Anthocyanin levels were assessed at 0, 7 and 11 days, respectively, with further valuation by RNA-seq under head-shading and light conditions. RNA sequences were de novo assembled into 50,329 unigenes, of which 38,701 were annotated against four public protein databases. Cluster analysis demonstrated that anthocyanin/phenylpropanoid biosynthesis, photosynthesis, and flavonoid biosynthesis in cluster 8 were the main metabolic pathways regulated by light and had showed associations with flower head growth. A total of 2,400 unigenes showed differential expression between the light and head-shading groups in cluster 8, including 650 co-expressed, 373 specifically expressed under shading conditions and 1,377 specifically expressed under normal light. Digital gene expression (DGE) analysis demonstrated that light perception and the signal transducers CRY3 and HY5 may control anthocyanin accumulation. Following shading, 15 structural genes involved in anthocyanin biosynthesis were downregulated, including PAL, C4H, 4CL, CHS, CHI, F3H and DFR. Moreover, six BoMYB genes (BoMYB6-1, BoMYB6-2, BoMYB6-3, BoMYB6-4, BoMYBL2-1 and BoMYBL2-2) and three BobHLH genes (BoTT8_5-1, BoTT8_5-2 and BoEGL5-3) were critical transcription factors controlling anthocyanin accumulation under light conditions. Based on these data, a light-associated anthocyanin biosynthesis pathway in Broccoli was proposed. This information could help improve broccoli properties, providing novel insights into the molecular mechanisms underpinning light-associated anthocyanin production in purple vegetables.

Grown to be Blue-Antioxidant Properties and Health Effects of Colored Vegetables. Part II: Leafy, Fruit, and Other Vegetables

The current trend for substituting synthetic compounds with natural ones in the design and production of functional and healthy foods has increased the research interest about natural colorants. Although coloring agents from plant origin are already used in the food and beverage industry, the market and consumer demands for novel and diverse food products are increasing and new plant sources are explored. Fresh vegetables are considered a good source of such compounds, especially when considering the great color diversity that exists among the various species or even the cultivars within the same species. In the present review we aim to present the most common species of colored vegetables, focusing on leafy and fruit vegetables, as well as on vegetables where other plant parts are commercially used, with special attention to blue color. The compounds that are responsible for the uncommon colors will be also presented and their beneficial health effects and antioxidant properties will be unraveled.