Bart Panis, Bioversity International, Belgium
More than 800 million people are undernourished and 200 million children under five years of age are underweight. Moreover, the world’s population is expected to reach 10,500 million by 2050. Reliable and sustainable improvements in yield will thus be needed to meet the demands of this growing population. The availability of the largest possible crop diversity is central to food security. Crop collections encompass seed propagated as well as vegetatively propagated crops. Seed is classically stored at -20°C (and sometimes cryopreserved) while vegetatively propagated crops are maintained in the field, stored as in vitro collection under reduced growth conditions or through cryopreservation. Cryopreservation plays an essential role in the safe conservation of plant genetic resources of vegetatively propagated crops like bananas, cassava, potato, yams and sweet potato. Cryopreservation research on these crops already started in the 80ties but it was only with the development of vitrification protocols and more recently with the use of droplet vitrification that a significant portion of such collections are now stored in liquid nitrogen. The droplet vitrification protocol was established because it combines the application of highly concentrated vitrification solutions (often PVS2) with ultra-fast freezing and thawing rates both leading to a lower chance of lethal ice crystal formation. Currently, over 10,000 accessions starting from in vitro cultures are safely preserved for the long term through cryopreservation. More than 80% of these belong to 5 crops; potato, cassava, bananas, mulberry and garlic. Other important cryopreserved collections representing thousands of accessions are those of dormant apple buds. One of the recommendations of an expert group to apply cryopreservation to a wider diversity of vegetatively propagated crops was to establish a collaborative effort among researchers and genebanks that is focused on the specific technical and practical issues.