Meet the Ancestors (of the past, present and future)

Making Crops Part II:

Even before humans cultivated crops they were using plants for food, fuel, construction materials and clothing. Archaeology has demonstrated that our human ancestors were very sophisticated when selecting plant materials and had a good understanding of their suitability for particular end-uses. As primitive crops were developed, selecting for the performance of the harvested product was as important as developing a crop that performed well in the field.

When comparing modern crops and their wild ancestors the most striking difference is their appearance. Many of these external characteristics (physical size and shape, and the size of grain, fruit or tubers) are important because they often directly affect yield. However, there are many non-obvious differences, in particular internal chemical changes, which are at least as significant as external appearance in determining the performance of the crop in the field and its suitability for its intended end use.

Of critical importance is the chemical composition of the harvested product. A plant's seeds, fruits or tubers may be large and attractive, but they may also be difficult to process because they do not soften when cooked or the grains are too hard (or soft) to grind easily. Wild ancestors often contain high levels of chemicals that are toxic to humans - these are sometimes the plants' defence against grazing animals or part of their chemical armoury against pests and diseases. Wild fruits, seeds and tubers may have unpleasant flavours or contain chemicals that cause "off-flavours" to develop after harvest. And some plants contain chemicals that prevent food being efficiently digested and absorbed in the stomach. The process of selecting and breeding improved crop types has reduced, or eliminated, many of these negative characteristics that were inherited from wild ancestors.

Typically the value of a crop is largely determined by the quality of the end product produced from it, whether this is an attractive, sweet tomato that keeps well, potatoes that do not fall apart when boiled or flour that makes a loaf with a good crumb structure. Breeders are increasingly able to breed crops that have end products tailored to particular end uses, for example different potato varieties that are suited to baking, boiling or making chips and crisps, and tomatoes that are 'designed' for processing or salad use.

These changes are all the result of changes in the internal chemistry of the plant. As scientists understand more about the internal chemistry and biology of plants so they are discovering there are major opportunities to create new crops and new crop products. This can be achieved in two ways, by taking existing crops and breeding them to make new products or by finding plants that make interesting products and domesticating them as new crops.

Research into how plants make starch and oil is leading to new varieties of familiar crops - like peas, potatoes and oilseed rape - that produce new types of oils and starches that can be used as renewable raw materials for making plastics, inks, paints, lubricants and adhesives. Other research is focussed on how to identify the entire genetic make up of a plant species and then recognise the key genes involved in controlling its performance in the field and the quality of the products it makes. This know-how could accelerate the rate at which novel crops, which make new oils, or other valuable products, could be developed from plants such as coriander, wild rocket and marigold. These are potentially the ancestors of the crops of the future.