ABSTRACT
All the major crops world-wide are the result of a repetitive process of breeding, selection and further breeding to alter characteristics and improve yield. Alongside this process have come great increases in human population as agricultural productivity has attempted to meet the needs of that population. For some crops, the process has been carried out only recently (e.g. for oil-seed rape, Canola) while for others it has been going on for many thousands of years and in many civilizations. Wheat was domesticated first in the near-East. Breadwheat appears to have resulted from crossing primitive einkorn wheat with goatgrass to generate emmer wheat, which was crossed again with goatgrass to yield bread wheat. Corn (maize) was domesticated in Mesoamerica. One of its closest relatives is teosinte, which produces small, corn-like seed ears with hard outer husks. Rice was domesticated in IndoChina from a wild rice, Oryza rufipogon. Apart from yield, domestication has altered many characteristics of crop plants, including loss of dormancy from the seed and loss of dispersal mechanisms. There are also some negative effects of domestication; for instance, domesticated varieties are frequently demanding of nutrients and soil conditions. Intensive breeding programmes resulting in near clonal crops may result in loss of biodiversity and susceptibility to disease.
