Genetic mapping of green curd gene Gr in cauliflower

Authors: TAN, HUAQIANG - Cornell University; WANG, XIN - Boyce Thompson Institute; CHAYUT, NOAM - Boyce Thompson Institute; LI, HUANXIU - Sichuan Agricultural University; TADMOR, YAAKOV - Agricultural Research Organization, Volcani Center; MAZOUREK, MICHAEL - Cornell University; Li, Li

Submitted to: Journal of Theoretical and Applied Genetics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/19/2019
Publication Date: 11/1/2019
Citation: Tan, H., Wang, X., Chayut, N., Li, H., Tadmor, Y., Mazourek, M., Li, L. 2019. Genetic mapping of green curd gene Gr in cauliflower. Journal of Theoretical and Applied Genetics. https://doi.org/10.1007/s00122-019-03466-2.
DOI: https://doi.org/10.1007/s00122-019-03466-2

Interpretive Summary: Cauliflower with colored curds enhances its visual appeal and nutritional value. Green cauliflower results from ectopic development of chloroplasts in the normal white curd, but the underlying genetic basis is unknown. In this study, by combining bulked-segregant analysis with next-generation whole genome resequencing and fine genetic mapping, we have identified the major locus responsible for the green curd color in cauliflower and delimitated it to a small genomic region with four most likely candidate genes. This study lays a solid foundation for isolation of the gene responsible for green curd color and provides a potential for marker-assisted selection of the green curd trait in cauliflower breeding. The eventual isolation of the green gene will also facilitate better understanding of chloroplast biogenesis and development in plants in general.

Technical Abstract: Cauliflower with colored curds enhances not only the visual appeal but also the nutritional value of the crop. Green cauliflower results from ectopic development of chloroplasts in the normal white curd. However, the underlying genetic basis is unknown. In this study, we employed QTL-seq analysis to identify the loci that were associated with green curd phenotype in cauliflower. A F2 population was generated following a cross between a white curd (Stovepipe) and a green curd (ACX800) cauliflower plants. By whole genome resequencing and SNP analysis of green and white F2 bulks, two QTLs on chromosome 5 (Gr5.1) and 7 (Gr7.1) were detected. Validation by traditional genetic mapping with CAPS markers suggested that Gr5.1 represented a major QTL, whereas Gr7.1 had a minor effect. Subsequent high-resolution mapping of Gr5.1 in the second large F2 population with additional 15 CAPS markers narrowed down the target region to a genetic and physical distance of 0.3 cM and 236 Kbp, respectively. This region contained 35 genes with four of them representing the best candidates underlying the green curd phenotype in cauliflower. They are LOC106295953, LOC106343833, LOC106345143, and LOC106295954, which encode UMP kinase, DEAD-box RNA helicase 51-like, glutathione S-transferase T3-like, and Protein MKS1, respectively. These findings lay a solid foundation for isolation of the Gr gene and provide a potential for marker-assisted selection of the green curd trait in cauliflower breeding. The eventual isolation of Gr will also facilitate better understanding of chloroplast biogenesis and development in plants.