ABSTRACT
Among cultivated oilseed crops are several members of the Brassicaceae that are grown for seed oil, condiments and seed meal. The major cultivated species are, Brassica napus, Brassica juncea, Brassica rapa, Brassica carinata and Brassica nigra. In addition, there is signifi cant interest in the cultivation of Sinapis alba. Conventional breeding was the main approach to the early adaptation of these species to temperate and subtropical growth conditions and signifi cant improvement was made in yield and oil quality (Stefanson and Hougen 1964; Harvey and Downey 1964; Becker et al. 1999). Brassica napus is now the dominant cultivated species and is grown on more than 25 million hectares worldwide (Commodity Research Bureau 2005). There are several factors likely to increase future demand for vegetable oils from crops such as Brassica oilseeds. The two main drivers are likely to be consumer demand for high quality oils with demonstrable health benefi ts and the trend towards the use of renewable resources as industrial feedstock for manufacture of polymers, biofuels, lubricants and other products, which are now derived from non-renewable resources. To meet this demand, will require a much more effi cient system of crop production where yield is maximized while input of resources is minimized. In addition, Brassica oilseeds will be required to deliver products for a variety of use and this necessitates modifi cation of fatty acid profi le and the protein quality of the seed meal. Plant performance is negatively affected by various biotic and abiotic stresses and tolerance to these stresses is a determinant of yield. For sustained high yield in the future, plants must have the genetic diversity to tolerate these stresses as well as those which are likely to be imposed by climate change where variation in temperature, radiation, atmospheric gases and water limitation will pose major challenges to yield (Watkins 2008; Challinor et al. 2009). Although conventional plant breeding has made a signifi cant contribution to the development of Brassica oilseed cultivars, reliance on the availability of benefi cial alleles in species that allow ready introgression into established cultivars is often limiting. Also, with conventional breeding phenotypic selection is often conducted with little or no knowledge of the regulation or function of genes responsible for
selected traits. Consequently, the breeding process is often time consuming and ineffi cient. However, the enormous body of knowledge arising from advances in molecular biology, basic plant biology and genomics is likely to accelerate the pace of Brassica oilseed crop improvement as genes and their functions can now be defi ned and their architecture detailed (Cooper et al. 2004). Therefore, modern plant breeding can now be conducted with a greater understanding of the factors determining phenotypic traits. As knowledge of the genetic control of the phenotype continues to accumulate through the application of genomics, cell and developmental biology and molecular biology, oilseed Brassica crops can be expected to play a very important role in the bio-economy through the delivery of a variety of products in a sustainable manner. The aim of this chapter is to provide an overview of the prospects and challenges for Brassica oilseed improvement in the era of genomics and with continued advances in cell biology and molecular biology.
