Brassica : Harvesting the Genome, Diversity and Products
illnesses such as Alzheimers, cataracts, and some of the functional declines associated with ageing. Plant secondary products have complementary and overlapping actions, including antioxidant effects from flavanoids and other phenolic compounds, modulation of detoxification enzymes, stimulation of the immune system, reduction of inflammation, modulation of steroid metabolism, and antibacterial and antiviral effects. Most studies show that phytochemicals in Brassica plants up-regulate many detoxification enzyme systems in the animal that consumes them.
Considerable genetic variation underlies products derived from plant cell biochemistry, which in turn affects the nutrients humans ingest. Underlying genetic variation has led to Brassica plants to produce higher amounts of particular compounds than do other plants in our diet.
The genes in the Brassicaceae uniquely enable the production of a particular class of biochemicals (glucosinolates) which break down to compounds (isothiocyanates such as sulphoraphane) known to provide some protection against a range of human cancers. Glucosinolates and other sulphur containing metabolites act as anti-cancer agents due to their ability to induce detoxification enzymes in mammalian cells and to reduce the rate of tumour development. Isothyocyanates are modulators of Phase 1 and 2 enzyme activity and neutralise cancer-causing chemicals that damage cells by interfering with tumour growth. The protective effect of Brassica consumption and the associated decrease in risk of cancer is related to the Human GST genotype. Significant effects are identified in cabbage and broccoli that have antiproliferative activities.
In vegetable brassicas, levels of vitamins A, C and E, folate and potassium are notably high. Brassica contains folates ranging from Glu4 to Glu8. Nutritional demands for folates are particularly high during pregnancy. Folate supplemenation prior to conception can significantly reduce the incidence of neural tube defects. Folate deficiencies have also been implicated in the etiology of megalobastic anemia, Spina bifida, neuropsychiatric disorders and various forms of cancer. There is also considerable scope for increasing levels of tocopherol (Vit E) in brassicas.
There is genetic variation in Brassica species for the uptake and availability of trace elements such as selenium (Se). Supplementation studies on humans have demonstrated the efficacy of Se for prevention of colon cancer. The metabolism of Se depends upon its chemical form, and the form that occurs in broccoli appears to be particularly effective at protecting laboratory animals from cancer
The fatty acid composition of Brassica seeds has been a target for selective breeding to meet different end uses and market demands. It has been shown that lipid profiles may have significant effects on human obesity, with emerging evidence to show that lipid profiles improve on a controlled-carbohydrate diet.
Since nervonic acid is an important constituent of brain and membrane phospholipids, it is vital that the body has an adequate provision of this fatty acid. If, for any reason, the body cannot make this lipid, then a dietary source is indicated. Two such situations are under active investigation; multiple sclerosis (MS), where there are indications that there is inadequate provision of nervonic acid; and premature birth, where the infant no longer benefits from maternal nutrition
A new iodised oil, Brassiodol utilises rapeseed oil as vehicle of iodination. Brassiodol This is proposed to prevent or eradicate 127I-deficiency disorders inlcuding goitre.
Agronomic adaptations and the genetic basis of trait variation
Within different growing regions and crop types there are priorities vary for research focused on agronomic traits. Dependent upon availability of natural or managed resource, the genetic variation within Brassica can be utilised to provide information and solutions to improve nutrient use efficiency, water use efficiency, germination, seedling establishment and vigour, yield components and the basis of genotype x environment interactions. As with all crops there is a continuing requirement to provide protection againsts pests and diseases.
Potential for increasing harvest index of a major oil crop
The harvest index (harvestable yield as a proportion of total biomass) of Brassica rapeseed crops is low compared with other arable crops such as cereals. There is considerable scope for improving the harvest index to increase overall yields and lower the level of fossil-fuel and other inputs for a more sustainable production. Developing a systems approach to understanding the genetic and genomic basis of yield components requires a multidisciplinary
Draft White Paper for Multinational Brassica Genome Project (MBGP); 12/01/2006