Plant Genetic Resources (PGR) have an important role to play to ensure global food and nutrition security. They have provided the foundation for crop improvement ever since agriculture began approximately 12,000 years ago. The paradox is that, while crop yield has expanded significantly over the past centuries, the continued introduction of new varieties and human mismanagement of the environment has threatened the very resource base (local land races and crop wild relatives (CWRs)) upon which its success is based. Today agriculture and food production are facing numerous challenges such as climate change, land degradation, soil impoverishment, pest and diseases epidemics, genetic erosion and so on. These challenges are each negatively affecting the way we are able to produce food in sustainable ways. Daily food security is becoming more and more dependent on the greater breadth of resources found in nature that are themselves being eroded or extinguished.

Increased conservation and use of CWRs is seen to be part of solution to fight these challenges and secure breadth of resources for crop improvement. CWRs are a source adapted genes for addressing biotic and abiotic stresses, as well as other breeding goals and yield and quality improvement. CWR importance to sustaining agriculture has been recognized internationally in Convention on Biological Diversity (Aichi target 13), International Treaty on PGRFA, FAO Global Plan of Action and The Sustainable development Goals (SDG 2- Zero Hunger) and has been valued at more than US$120 billion (PwC, 2013). Despite their economic importance to agriculture and the role they have played in shaping our food crops over centuries, the conservation of CWR remains an under-funded research area, with global 72% of CWR taxa requiring additional ex situ collections (Castañeda-Álvarez et al., Reference Castañeda-Álvarez, Khoury, Achicanoy, Bernau, Dempewolf, Eastwood, Guarino, Harker, Jarvis, Maxted, Müller, Ramírez-Villegas, Sosa, Struik, Vincent and Toll2016) and there being no effective in situ conservation of CWR populations in nature (Maxted et al., Reference Maxted, Amri, Castañeda-Álvarez, Dias, Dulloo, Fielder, Ford-Lloyd, Iriondo, Magos Brehm, Nilsen, Thormann, Vincent, Kell, Maxted, Ehsan Dulloo and Ford-Lloyd2016).

However, in the last few decades significant progress toward effective conservation has been made; there is a growing body of work focusing on develop methodologies and tools for the sustainable conservation and use of CWR (Iriondo et al., Reference Iriondo, Maxted and Dulloo2008; Maxted et al., Reference Maxted, Dulloo, Ford-Lloyd, Iriondo and Jarvis2008, Reference Maxted, Kell, Ford-Lloyd, Dulloo and Toledo2012, Reference Maxted, Avagyan, Frese, Iriondo, Magos Brehm, Singer and Kell2015, Reference Maxted, Amri, Castañeda-Álvarez, Dias, Dulloo, Fielder, Ford-Lloyd, Iriondo, Magos Brehm, Nilsen, Thormann, Vincent, Kell, Maxted, Ehsan Dulloo and Ford-Lloyd2016; Iriondo et al., Reference Iriondo, Maxted, Kell, Ford-Lloyd, Lara-Romero, Labokas, Magos Brehm, Maxted, Dulloo, Ford-Lloyd, Frese, Iriondo and Pinheiro de Carvalho2012). Numerous projects aiming at developing national or genepool conservation strategies, action plans and gap analysis for CWR conservation have been undertaken in various part of the world. In the recent years we have seen a revival of interest to better understand the diversity, distribution of CWR and gaps in conservation and their threat status. Efforts to prioritize CWR taxa globally (Vincent et al., Reference Vincent, Wiersema, Kell, Fielder, Dobbie, Casteñeda-Álvarez, Guarino, Eastwood, León and Maxted2013), then collect and conserve CWR in genebanks is being undertaken at a large scale for priority crops in the world (Dempewolf et al., Reference Dempewolf, Eastwood, Guarino, Khoury, Müller and Toll2013) and most recently global priority locations for in situ conservation have been identified (Vincent et al., Reference Vincent, Amri, Castañeda-Álvarez, Dempewolf, Dulloo, Guarino, Hole, Mba, Toledo and Maxted2019). Yet today breeders creation of novel varieties and who are increasingly looking at CWR for adaptive and resistance traits, find crop improvement restrained by lack of CWR germplasm or the necessary characterization information (McCouch et al., Reference McCouch, Baute, Bradeen, Bramel, Bretting, Buckler, Burke, Charest, Cloutier, Cole, Dempewolf, Dingkuhn, Feuillet, Gepts, Grattapaglia, Guarino, Jackson, Knapp, Langridge, Lawton-Rauh, Lijua, Lusty, Michael, Myles, Naito, Nelson, Pontarollo, Richards, Rieseberg, Ross-Ibarra, Rounsley, Sackville Hamilton, Schurr, Stein, Tomooka, van der Knaap, van Tassel, Toll, Valls, Varshney, Ward, Waugh, Wenzl and Zamir2013).

Therefore, this Special Volume of Plant Genetic Resources, Characterization and Evaluation is very timely as CWR science finally moves beyond the theoretical to the increasing applied, to meet breeders and consumers growing demands. It includes prioritized CWR inventories at different geographical levels viz. national (Bissessur et al., Reference Bissessur, Baider, Boodia, Badaloo, Bégué, Jhumka, Meunier, Mungroo, Gopal, Kell, Magos Brehm, Thormann and Jaufeerally-Fakim2019; Dickson et al., Reference Dickson, Munkombwe, Mwila, Gaisberger, Magos Brehm, Maxted, Kell and Thormann2019), regional (Allen et al., Reference Allen, Gaisberger, Magos Brehm, Maxted, Thormann, Lupupa, Dulloo and Kell2019; Fitzgerald et al., Reference Fitzgerald, Palmé, Asdal, Endresen, Kiviharju, Lund, Rasmussen, Thorbjornsson and Weibull2019) levels. Tools to facilitate conservation planning have also been developed (Magos Brehm et al., Reference Magos Brehm, Kell, Thormann, Gaisberger, Dulloo and Maxted2019; Holness et al., Reference Holness, Hamer, Magos Brehm and Raimondo2019), and regional conservation strategies and approaches have been developed (Allen et al., Reference Allen, Gaisberger, Magos Brehm, Maxted, Thormann, Lupupa, Dulloo and Kell2019; Kell et al., Reference Kell, Magos Brehm, Allen, Gaisberger, Dulloo, Thormann and Maxted2016).

Many of the papers included in this special issue are focused on CWR conservation in Southern Africa, a region where agricultural production is often stressed to climate change, is predicted to have a significant deleterious impact, so improving CWR conservation could make the difference between food insecurity and security for millions. The work is undertaken within the ACP-EU funded project ‘In situ conservation and use of crop wild relatives in three ACP countries of the SADC region’ (SADC Crop Wild Relatives project) (http://www.cropwildrelatives.org/sadc-cwr-project/) and implemented through the ACP-EU Co-operation Programme in Science and Technology (S&T II by the ACP Group of States (grant agreement no. FED/2013/330-210)). Work in this region is complemented with CWR studies from other regions (Contreras-Toleda et al., Reference Contreras-Toleda, Cortés-Cruz, Costich, Rico-Arce, Magos Brehm and Maxted2019; Fitzgerald et al., Reference Fitzgerald, Palmé, Asdal, Endresen, Kiviharju, Lund, Rasmussen, Thorbjornsson and Weibull2019; Philips et al., Reference Philips, Whitehouse and Maxted2019; Tas et al., Reference Tas, George West, Gun Kircalioglu, Boyraz Topaloğlu, Phillips, Kell and Maxted2019).