The use of wild relatives in crop improvement: A survey of developments over the last 20 years

The use of crop wild relatives (CWR) genes to improve crop performance is well established with important examples dating back more than 60 years. In this paper, we review available information on the presence of genes from CWR in released cultivars of 16 mandate crops of the CGIAR institutes, and some selected additional crops, focusing on the past 20 years-the period since a comprehensive review by Robert and Christine Prescott-Allen in 1986. It appears that there has been a steady increase in the rate of release of cultivars containing genes from CWR. While there continues to be a strong emphasis on using pest and disease resistance genes, a wider range of characteristics are being introduced than in the past. Those crops whose wild relatives have traditionally been used as sources of useful traits (e.g., wheat, tomato) continue to be most likely to include new genes from their wild relatives. CWR are continually gaining in importance and prevalence, but, we argue, their contributions to the development of new cultivars remain less than might have been expected given improved procedures for intercrossing species from different gene pools, advances in molecular methods for managing backcrossing programes, increased numbers of wild species accessions in gene banks, and the substantial literature on beneficial traits associated with wild relatives.