Crop wild relatives (CWR) - distant wild cousins of major food crops - are widely recognised as one of the most important resources available to plant breeders in the fight against climate change and pests. However, experts are seriously concerned by the lack of CWR specimens in genebanks around the world.

According to a new report by the International Centre for Tropical Agriculture (CIAT), the Global Crop Diversity Trust (Crop Trust) and the Royal Botanic Gardens (RBG) at Kew, not only does the lack of specimens mean breeders may be missing out on useful traits now, but many habitats of these potentially vital plants are under threat from urbanisation, pollution, deforestation, climate change and war.

Policy makers are beginning to appreciate the importance of crop wild relatives, as the effects of climate change become more apparent; as it worsens - and in addition to growing environmental challenges - climate change threatens to bring diseases and pests to new areas, meaning breeding adaptable crops will be vital for the future of farming. The valuable genetic diversity possessed by CRW plants could be used to breed crops that can thrive in higher temperatures, more saline soils, drier conditions and areas more prone to flooding. They could also go some way towards redressing the loss of genetic diversity that occurred in agricultural crops over the course of the 21st Century.
 
Key findings of the project, which mapped 1,076 wild relatives of the world's 81 most important crops, include:

• 29% of the total, or 313 wild relative plant species analysed, are completely missing from the world's gene banks
• A further 257 (23.9%) of species are represented by fewer than 10 samples having been collected for each, leaving out a substantial amount of potentially important plant diversity.
• Over 70% of the total crop wild relative species are in urgent need of collection and conservation to improve their representation in gene banks
• Over 95% are insufficiently represented in regard to the full range of geographic and ecological variation in their native distributions.
• The most critical collecting gaps occur in the Mediterranean and Near East; western and southern Europe; Southeast and East Asia; and South America.
• Wild relatives of banana, sorghum and sweet potato are in urgent need of collection, alongside many other fruits and vegetables

Though earlier research has warned of gaps in gene bank collections, the authors of the CIAT analysis, published on Monday, believe theirs is the most comprehensive list showing gaps in collections and areas most at risk. CIAT scientist Nora Castañeda-Álvarez said the research "establishes a baseline for how well we are protecting crop wild relatives worldwide."

She added, ”There are big gaps for many crops and in many regions. It’s now clear that scientists around the world are in a race against time to collect and conserve many of the most important plant species for future food security."

Castañeda-Álvarez said that wild relatives of carrot, spinach, and many other fruits and vegetables are seriously under represented, and that though the wild relatives of vital staples like rice, wheat, potato, and maize tend to be better represented in gene banks, there are still significant gaps in the world’s collections.

CIAT scientist Colin Khoury said, ”The overall level of exposure to risk is really troubling. The world's food supply is in a precarious position of depending on too few crop plant species. For every CWR that's not conserved in a gene bank and available for research, it means there is one less option for plant breeders to improve the resilience of the food crops we rely on so much."

"Our findings give us the clearest idea yet of which plants are missing and where in the world we need to search for them.”

The value of crop wild relatives as a resource has already been proven. Genes from a wild rice species Oryza nivara were instrumental in helping to develop rice varieties resistant to the grassy stunt virus, a disease that caused hundreds of millions of dollars of damage to Asian farmers in the 1970s. The UN has recognised the importance of their preservation in article 2.5 of the Sustainable Development Goals, which includes a call to maintain the genetic diversity of seeds, including crop wild relatives, in gene banks by 2020.

The Crop Trust and RBG Kew are working to fill the gaps, and researchers said the new analysis will help them prioritise the most urgent cases.