Submitted to: Theoretical and Applied Genetics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/15/2007
Publication Date: 5/22/2007
Citation: Gao, M., Li, G., Yang, B., Qiu, D., Farnham, M.W., Quiros, C. 2007. High Density Brassica Oleracea Linkage Map: Identification of Useful New Linkages. Theoretical and Applied Genetics. 115:277-287.
Interpretive Summary: Broccoli, cabbage, cauliflower, collard and several other vegetables are all part of a family of crops that fall under a single plant species called Brassica oleracea. These crops are called cruciferous plants and are among the most important vegetables grown and consumed in the United States. Their total value to the United States economy is approximately one billion dollars. There is increased interest in the public and private sectors to enhance different characteristics, such as disease and pest resistance, environmental stress tolerance, and nutritional content, of these cruciferous vegetables. To better manipulate or improve the above traits it is useful to identify genetic or DNA factors that control or influence these characters and also to understand the relationship of all factors within the plant’s total genetic makeup. This identification and organization of all DNA factors in a plant species is called a DNA map and it is an important tool or aid in plant genetic improvement. In this study, we developed a very detailed DNA map for the broccoli and cauliflower family. This map is made up of different types of DNA factors and includes the location of a number of important and specific genes like the one that controls downy mildew resistance and another that is influential in the formation of cauliflower curds. This described map will prove to be an important tool for a variety of plant breeders and geneticists focused on improving these crops for many different traits.
Technical Abstract: We constructed a 1257-marker, high-density genetic map of Brassica oleracea spanning 703cM in nine linkage groups, named LG1-LG9. It was developed in a F2 segregating population of 143 individuals obtained by crossing two double-haploid plants of broccoli Early-Big and cauliflower An-Nan Early. These markers are uniformly distributed throughout the map, which includes a total of 1062 genomic SRAP markers, 155 cDNA SRAP makers, 26 SSR markers, 3 broccoli BAC end sequences and 11 known Brassica genes [BoGSL-ALK, BoGSL-ELONG, BoGSL-PROa , BoGSL-PROb, BoCS-lyase, BoGS-OH, BoCYP79F1, BoS-GT (glucosinolate pathway), BoDM1 (resistance to downy mildew), BoCALa, and BoAP1a (inflorescence architecture)]. BoDM1 and BoGSL-ELONG are linked on LG 2 at 0.8cM, making possible to use the glucosinolate gene as a marker for the disease resistance gene. By QTL analysis, we found three segments involved in curd formation in cauliflower. The map was aligned to the C genome linkage groups and chromosomes of B. oleracea and B. napus and anchored to the physical map of A. thaliana. This map adds over 1000 new markers to the current B. oleracea consensus map, expanding it to 1806 markers.