The Many Faces of Brassica oleraceaOur story begins on the windswept, limy cliffs along the Atlantic Ocean and Mediterranean Sea, perhaps 4000 years ago. Here grew a leafy herbaceous plant with succulent, edible leaves that modern botanists call Brassica oleracea. In this part of the world plants were able to grow throughout the year, thereby providing an important source of vitamins and trace elements during even the winter months. It thus became an important part of the diet of the people living by these shores. Eventually its seeds were collected and plants were grown within human settlements, where it was spread across Eurasia. This barely-domesticated plant looked very close to what we now know as ‘kale.’ The name used to identify this crop descends far back into Eurasian civilization, with ‘kaulis’ being the likely term used in the hypothesized Proto Indo-European language. From this root springs varied names across the ancient world: The Hindi called them ‘kopi’; the Tartars ‘kappes’; the Greeks ‘kaulion’; the Romans ‘coles’; the Anglo-Saxons ‘colewyrts’. From these come the German ‘kohl’, the Norwegian ‘kaal’, the Spanish ‘col’, the Scottish Gaelic ‘kale’ and the English ‘collards’. Sometime before 3000 years ago, people began selecting for varying and different traits from within this single plant, giving rise to a shocking variety of vegetables. It is now hard to imagine that kale and collard greens, cauliflower, cabbage, kohlrabi, broccoli, cabbage, and brussels sprouts all originated from the same wild plant. Within each, a different part was bred to be the focus for consumption. We start with ‘kale’ and ‘collards’ (known botanically as the Acephala Group) which represents those crops most closely related to the primeval wild plant: in these, selection was for the quantity, size, color, and appearance of the leaves. Later (perhaps 2000 years ago), farmers in the Mediterranean began selecting for plants with larger and more dense flower heads, with thicker and more succulent stems supporting those flowers. The varieties in which the flower heads and stems remained green became ‘broccoli’ (the Italica Group) while those which were selected to be light-green or white became ‘romanesco broccoli’ or ‘cauliflower’ (the Botrytis Group). At this same time, plant breeders in China and Southeast Asia independently bred a plant similar to broccoli but with larger leaves, a somewhat smaller flower head, and a slightly more bitter flavor (the Alboglabra Group). These are called ‘kai-lan’ or ‘Chinese broccoli’. While broccoli initially did not stray far from its Mediterranean roots, cauliflower rapidly spread east across the near east to India, where it became an important part of the regional diet. Within the last few decades modern plant breeders have further selected for a number of additional cauliflower colors including orange and purple. Northern European farmers continued developing this plant. Around 1000 years ago, during the Dark Ages, plant breeders began selecting for kales with shorter and shorter distances between leaves along the stem. This eventually gave rise to cabbages (the Capitata Group); in fact ‘cabbage’ is derived from ‘caboce’, the Old French word for ‘head’. The crinkly-leaved Savoy cabbage was developed by German gardeners only 300 years ago. During the late Middle Ages, about 600 years ago, another group of Northern European farmers began selecting for kales with thicker stems to create a ‘kale turnip’. This became kohlrabi (the Gongylodes Group) from the German ‘kohl’ (kale) and ‘rabi’ (turnip). It rapidly spread east across Eurasia to Siberia and India. At this same time, plant breeders in the Low Countries began selecting for tall kales that produced small leafy heads on the axillary buds above each leaf. These became Brussels sprouts (the Gemmifera Group). The story does not quite end here. Brassica rapa is a closely related species which was initially domesticated in Europe around 4000 years ago and rapidly spread east into India, China, and Japan. It was selected for various traits including oil rich seeds, numerous fleshy leaves (the eastern ‘cabbages’ and ‘mustards’ which include mizuna, bok choy, and napa cabbage), thick tuberous roots (turnips), and fleshy leaves and flower stalks (broccoli rabe). This species can hybridize with Brassica oleracea, creating a new species (Brassica napus) which has a different number of chromosomes (n = 19) from its two parents (Brassica oleracea, n = 9; Brassica rapa, n = 10). This new species was then similarly selected for oil rich seeds (rapeseed, which is known in North America as the less violent-sounding ‘canola’), tuberous roots (rutabaga / swedes), or dense leaf growth (Siberian kale). Archive |
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