DNA Markers in Brassica: Use of Genetic Information from Arabidopsis and Development of Sequence Tagged Site Markers

Abstract

The genus Brassica is part of a taxon grown worldwide and includes important vegetables and oil crops. Cultivation of Brassica is thought to have started in the Neolithic age (Kimber and McGregor 1995), and since that time, Brassica crops have been exposed to intensive selection throughout the world. As a result, they have diversified into many types of vegetables, oilseeds, condiments and forages (reviewed by Tsunoda 1980). Using conventional taxonomic and cytological criteria, Brassica species are classified into six species, three of which are diploid: B. rapa = AA, B. oleracea = CC, B. nigra = BB. The remaining three species are amphidiploids (B. napus = AACC, B. carinata = BBCC, B. juncea = AABB), derivatives of the diploid species. The relationships between the A, B and C genomes were established by U who successfully produced artificial amphidiploids (U 1935), and the relationship became known as the “triangle of U”. Subsequent interspecific hybridization among the diploid species revealed common ancestral chromosomes in Brassica (reviewed by Mizushima 1980). Plant breeders have exploited the high success rate of interspecific crosses to transfer numerous desirable agronomic characteristics into several Brassica species. In addition to the significant cross-ability, Brassica species possess a pollination system involving several series of self-incompatible (SI) alleles, thus creating complicated genetic backgrounds (reviewed by Hinata and Nishio 1980). Recent progress in plant biotechnology has produced novel breeding tools such as microspore culture (Downey and Rimmer 1993), hybrid seed production (Buzza 1995), genetic transformation (Nap et al. 2003) and DNA markers. These techniques have been incorporated into Brassica breeding regimens and are routinely used for the efficient production of elite lines. In this chapter, we describe recent developments in the use of DNA markers in both vegetable and oilseed Brassica breeding. In the early 1990s, restriction fragment length polymorphism (RFLP) analysis was utilized to detect genetic diversity and construct genetic maps in Brassica; linkage maps of several Brassica species have been demonstrated by