ABSTRACT
In this chapter, we outline differences between three kinds of plants — domesticated crops, agricultural weeds, and feral crop plants. Both domesticated crops and agricultural weeds have arisen from wild plants, but domesticated crops are different, as they are mostly human inventions selected for certain traits through thousands of years. We will first describe the crop domestication process and the evolution of agricultural weeds in general, contrasting “domestication” with “weediness” traits acquired during the dedomestication or ferality process, including a review of their genetic basis. Then for a select group of crop plants we will examine the degree of inferred domestication (ratio of domestic acquired to retained weediness traits). We will also discuss the evidence from the “world-weed” literature to analyze the extent that agronomic problems or losses involve weed species that are either crops or weedy plants that are coadapted and related to crops. As other chapters deal with specific crops, we focus on an examination of genetic factors (e.g., linkage disequilibrium) that might affect crop ferality in general and then briefly describe how biotechnological factors (e.g., transgenes) might affect ferality. However, before we do this, we must briefly examine the concepts of plant domestication, weediness, and ferality.
