The extraordinary diversity of plants arises from differences in their genetic constitution, coupled with the way in which these combinations of genes control the development of the plant from seed to adult form.
Thus, bread wheat arose from a cross between a cultivated wheat and a wild goat grass (Aegilops squarrosa) about 10,000 years ago in farmers’ fields in northern Iran. The genetic constitution of the goat-grass gave bread wheat tolerance to cold and wet. As seed of this hardier strain of bread-wheat was selected generation after generation, arable farming spread into the colder temperate regions of the world from its centre of origin in the Middle East.
For thousands of years, humans have developed a whole range of crop varieties with different uses, by selecting variations arising within single species such as wild cabbage or wild beet. In nature, the wild cabbage is a maritime cliff plant rather like kale. Artificial selection of different genetic combinations has given rise to varieties as diverse as brussels sprouts, red cabbage, cauliflower and kohlrabi, in which the development of different parts of the plant has been altered. Wild beet was probably first brought into cultivation by the Romans who used it as a leaf vegetable. Selections have given rise to spinach beet, beetroot, sugar beet and rhubarb chard. The Genetics Garden shows many of these selection stories, so by late summer the display resembles a well-tended allotment!
The display focuses on new crops for the future while it pays homage to the past by re-creating the hybridisation experiments undertaken here at the Botanic Garden by Cambridge zoologist William Bateson at the turn of the twentieth century after his re-discovery of the work of monk, Gregor Mendel. Together with collaborators R C Punnett and Edith Saunders, Bateson’s major contribution to genetics (a word he invented) came from studies on sweet peas (Lathyrus odoratus). They found that, remarkably, crossing a white- by a white-flowered plant gave a full-coloured offspring and concluded that two independent genes controlled flower colour, so separating the analysis of genes from the characters they determined. We repeat this classic experiment each year in the Genetics Garden.
In response to the increasing use of this planting for secondary school teaching, the interpretation boards in the Genetics Garden have recently been reworked in collaboration with the National Institute of Agricultural Botany (NIAB).