Review of congruence between global crop wild relative hotspots and centres of crop origin/diversity

Crop wild relatives (CWR) are important sources of adaptive diversity for plant breeding programmes. This paper aims to investigate the extent to which the centres of crop origin/diversity are congruent with areas of high CWR diversity. We established the predicted potential CWR distributions for 1,425 CWR species related to 167 crops using 334,527 known distribution locations and generated a global CWR hotspot map. This was then compared to the centres of origin/diversity proposed by Vavilov (amended by Hawkes); Zeven and Zhukovsky's mega gene centres, Harlan's centres and non-centres of crop domestication; and crop domestication areas identified using current archaeological evidence proposed by Purugganan and Fuller. Greatest congruence between the global CWR hotspots and other concepts was found with the concept proposed by Vavilov and amended by Hawkes, but there remained significant differences between the CWR hotspots and Vavilov's concept. This paper concludes that all four centre concepts reviewed have some overlap with CWR diversity but that Vavilov's original concept has the closest geographic coincidence with CWR hotspots. With the benefit of significant additional global datasets to those used by Vavilov, we were able to suggest amendments to his concept, adding further centres based on CWR hotspots in west and east USA, West Africa, South-east Brazil and Australia. As a result of this study more precise targeting of CWR and crop landrace can be implemented in future, aiding global food and nutritional security.