Rapid Cycling Populations of Brassica Author s Paul H Williams and Curtis B Hill Source Science New Series Vol 232 No 4756 Jun 13 1986 pp 1385 1389 Published by American Association for the Advancement of Science Stable URL http www jstor org stable 1697720 Accessed 15 07 2008 17 22 Your use of the JSTOR archive indicates your acceptance of JSTOR s Terms and Conditions of Use available at http www jstor org page info about policies terms jsp JSTOR s Terms and Conditions of Use provides in part that unless you have obtained prior permission you may not download an entire issue of a journal or multiple copies of articles and you may use content in the JSTOR archive only for your personal non commercial use Please contact the publisher regarding any further use of this work Publisher contact information may be obtained at http www jstor org action showPublisher publisherCode aaas Each copy of any part of a JSTOR transmission must contain the same copyright notice that appears on the screen or printed page of such transmission JSTOR is a not for profit organization founded in 1995 to build trusted digital archives for scholarship We work with the scholarly community to preserve their work and the materials they rely upon and to build a common research platform that promotes the discovery and use of these resources For more information about JSTOR please contact support jstor org http www jstor org I Rapid Cycling Populations PAUL H WILLIAMS Rapid cycling populations of six economically important species in the genus Brassica have unusual potential for resolving many problems in plant biology and for use in education Rapid cycling brassicas can produce up to ten generations of seed per year and serve as models for research in genetics host parasite relations molecular biology cell biology plant biochemistry population biology and plant breeding Brassicas are a highly diverse group of crop plants that have great economic value as vegetables and as sources of condiment mustard edible and industrial oil animal fodder and green manure These plants can also be used in the classroom as convenient rapidly responding living plant materials for hands on learning at all levels of our educational system AJOR ADVANCES IN BIOLOGY OFTEN COME WHEN DI verse disciplines focus on model organisms An essential reason why many microbes Drosophila and mice have continued to be useful as research models is that their genetic information can be readily studied by the developing technologies in molecular biology These organisms have rapid reproductive cycles and are amenable to laboratory culture in large numbers Among the higher plants a short cycled member of the cabbage family Arabidopsisthaliana has emerged as an important model plant for research in molecular genetics 1 Species in the genus Brassica also in the cabbage family have unusual potential as models for studying plant systems Diversity Biology and Production The brassicas are a diverse group of crop plants with great economic value worldwide These plants produce condiment mustard leafy stored processed and pickled vegetables seed oils for margarine salad oil cooking oil plastic and industrial uses animal fodders and green manures for soil rejuvenation 2 Although brassicas are known in the United States mainly as highly nutritious vegetables cabbage cauliflower broccoli collard kale mustard greens and Chinese cabbage their potential value as oilseed crops and animal fodder is just beginning to be recognized 3 Crucifer oil known as rapeseed oil is the fourth most commonly traded vegetable oil in the world Rapeseed contains 40 oil which is pressed from the seed leaving a high protein seed meal of value for animal feed and nitrogen fertilizer 4 Most Northern European countries produce rapeseed as their main edible oil crop Salt tolerant rapeseed is one of the first crops grown on the reclaimed polder land in Holland China and India each grow rapeseed on over 3 million hectares and Canada exports rapeseed 13 JUNE I986 AND CURTIS of Brassica B HILL Canola produced on 4 million hectares An important component of some rapeseed varieties is the 22 carbon unsaturated fatty acid erucic acid 22 1 Erucic acid is a component of resins and lubrication oils for jet engines and is used in steel manufacturing Since it interfereswith mammalian metabolism only plants containing little or no erucic acid are grown for human and animal consumption 5 Brassicasare also grown for animal fodder in regions too cool for maize or during winter months when grass grows slowly Large acreagesof turnips rutabagas leafy forms of cabbage and kales with thickened succulent stems provide winter grazing for sheep and cattle in Northern Europe and New Zealand Brassica oil and vegetables are an essential part of the diets of many developing nations The Chinese consume 0 25 kilogram of crucifer vegetables per capita daily and in Korea consumption is even higher A close relative of Brassica radish genus Raphanus is grown as a vegetable in China Korea Japan and India where many large root types are dried brined pickled cooked or fed to animals The six major Brassicaspecies of economic importance exist in a naturalrelationship that was described by the genetic and cytogenetic work of U and Morinaga 6 Fig 1 Three diploid species B nigra bb B campestris aa syn B rapa and B oleracea cc are the progenitors of the naturally occurring allotetraploid species B juncea aabb B napus aacc and B carinata bbcc Diploid B campestris aa therefore has 20 chromosomes and allotetraploid B juncea aabb has 36 chromosomes Within each of the species there are a range of forms that represent divergent selection during domestication Table 1 Within B oleraceaare cole crops such as cabbage cauliflower curly kale kohlrabi and Brussels sprouts and the bizarretree cabbage or Jersey kale Tree cabbage which may be up to 3 meters tall is grown on the Channel Islands where the leaves are stripped from the stem as cattle feed in winter and the remaining stalks are cut and dried for manufacture as walking sticks 7 Several oilseed types are found within B campestris as well as Chinese cabbage turnip pak choi and a host of other forms representing vegetables consumed in various Oriental cultures Brassicajuncea generally known as mustard also displays a wide divergence of form and is used as a source of oilseed in India and Pakistan and as a vegetable in western central China The sharp mustard flavor is imparted by high levels