Challenges of In Situ Conservation of Crop Wild Relatives

Turk J Bot 32 (2008) 421-432 © TÜBİTAK Challenges of In Situ Conservation of Crop Wild Relatives Vernon Hilton HEYWOOD Plant Science Laboratories, School of Biological Sciences, University of Reading, Reading RG6 6AS - UK Received: 17.09.2008 Accepted: 04.11.2008 Abstract: Crop wild relatives (CWRs) will gain in importance as changing climates put both traditional and advanced cultivars under increasing stress, leading to a need for plant breeding to produce new varieties able to grow under the new climate regimes. Traditionally, the approach to the conservation of CWRs has been ex situ – the collection and maintenance of seed accessions in national, regional, and international germplasm banks, supplemented by field genebanks for species with recalcitrant seeds. More recently the need to maintain CWRs in their natural habitats (in situ) has been advocated. This is very different from on-farm conservation of traditional land races and is a complex multidisciplinary process. Particular problems that have to be addressed include the adoption of a workable definition of what is a CWR, application of priority-determining mechanisms because of the large number of candidate species of CWRs, assessment of the effectiveness of conservation approaches, the relative costs of in situ and ex situ approaches, integration of CWR in situ conservation into national programmes, and the challenges posed by global change. CWRs may be conserved in both protected and non-protected areas. Presence in the former is no guarantee of their survival and in most cases some degree of management intervention is required. Experience derived from recent EU- and GEF-funded CWR conservation initiatives will be drawn upon. Key Words: Crop wild relatives, conservation, in situ, global climate change Introduction The importance of CWRs In the introduction to Hoyt’s Conserving the Wild Relatives of Crops (1998), IBPGR, IUCN, and WWF wrote ‘The conservation of crop genetic resources–the plants that feed us and their wild relatives–is one of the most important issues for humankind today’. This statement is as true, if not more so today, as when it was written 20 years ago. One of the challenges of global change now facing us is how to provide adequate nutrition for the steadily growing world population in the face of changing climatic conditions and continuing habitat loss. In meeting that challenge, as wide a range as possible of genetic material will be needed to breed the new cultivars required and crop wild relatives will be an important source of that variation. As an economic appraisal of crop genetic resources from the United States Department of Agriculture notes, crop genetic resources are essential to maintaining and improving agricultural productivity: ‘Without continued genetic enhancement using diverse germplasm from both wild and modified sources, the gains in crop yields obtained over the past seven decades are not sustainable, and yields might eventually grow more slowly or even decline. Agricultural production increasingly relies on “temporal diversity,” changing varieties more frequently to maintain resistance to pests and diseases’ (Rubenstein et al., 2005). In fact, it is likely that in situ genetic variation of crop wild relatives will now be of more value to plant breeders, especially in the light of recent advances in biotechnology which allow breeders increasingly to use genetic material found in wild populations. Furthermore, these populations contain valuable alleles at low frequencies that have so far evaded capture in previous sampling and breeding programmes (Williams, 1991; Franks, 1999). On the other hand, Hajjar and Hodgkin (2007) argue that despite such molecular and other improved procedures, the contributions of crop wild relatives to the development of new cultivars are less than they might have been expected, and so clearly there is great potential still to be exploited (but cf. Rubenstein et al., 2006). * E-mail: 421 Challenges of In Situ Conservation of Crop Wild Relatives In today’s context of global change, Lane (2007) notes, ‘The irony … is that plant breeders will be relying on wild relatives more than ever as they work to develop domesticated crops that can adapt to changing climate conditions. Yet because of climate change, we could end up losing a significant amount of these critical genetic resources at precisely the time they are most needed to maintain agricultural production’. The likely impacts of climate change on crop wild relatives will be considered below. Crop Wild Relatives in SW Asia As Erna Bennett reminded us at the first Plant Life of South-West Asia conference in Edinburgh in 1970 (Bennett, 1971), the region is one of the cradles of cultivated plants and indeed of Western civilisation. Hundreds of crop wild relatives occur in the region1, including cereals such as wheat (Triticum), barley (Hordeum), rye (Secale), Aegilops, legumes such as lentil (Lens), chickpea (Cicer), fodder plants (Medicago, Onobrychis), and in particular many fruits such as cherries (Prunus), pears (Pyrus), apples (Malus), plum (Prunus), pomegranate (Punica), quince (Cydonia), azarole (Crataegus), medlar (Mespilus), figs (Ficus), and grapevine (Vitis), and nuts such as hazelnut (Corylus), walnut (Juglans), and pistacio (Pistacia). It is appropriate therefore to consider what advances have been made in the conservation and sustainable use of these valuable resources in the intervening years. The natural landscapes of SW Asia have been subjected to considerable change over the past decades as a result of change in land use, alterations in disturbance regimes, loss of habitats or their conversion for agricultural use, and climatic fluctuations, all of which have adversely affected the populations of crop wild relatives that occur there. Coordinated action is urgently needed to ensure that as much as possible of this important genetic variation survives for present and future generations. Because of the international dimensions of crop genetic resources, this is not just a problem that affects the region, but is of global significance. 1 Problems of definition of crop wild relatives The term crop wild relative is not a precise one and has been variously defined and debated. Meilleur and Hodgkin (2004) consider that a workable, consensusdriven definition would help clarify discussions of the topic and direct efforts more effectively and suggest as a possible definition that ‘CWRs should include the wild congeners or closely related species of a domesticated crop or plant species, including relatives of species cultivated for medicinal, forestry, forage, or ornamental reasons’. In general terms, a CWR is a plant that is more or less closely related to a crop and to which it may contribute genetic material, but unlike the crop species has not been domesticated; they are also likely to be the progenitors or direct ancestors of crops. Crops are interpreted here as includ (...truncated)