Search

Crop landraces have unique local agroecological and societal functions and offer important genetic resources for plant breeding. Recognition of the value of landrace diversity and concern about its erosion on farms have led to sustained efforts to establish ex situ collections worldwide. The degree to which these efforts have succeeded in conserving landraces has not been comprehensively assessed. Here we modelled the potential distributions of eco-geographically distinguishable groups of landraces of 25 cereal, pulse and starchy root/tuber/fruit crops within their geographic regions of diversity. We then analysed the extent to which these landrace groups are represented in genebank collections, using geographic and ecological coverage metrics as a proxy for genetic diversity. We find that ex situ conservation of landrace groups is currently moderately comprehensive on average, with substantial variation among crops; a mean of 63% ± 12.6% of distributions is currently represented in genebanks. Breadfruit, bananas and plantains, lentils, common beans, chickpeas, barley and bread wheat landrace groups are among the most fully represented, whereas the largest conservation gaps persist for pearl millet, yams, finger millet, groundnut, potatoes and peas. Geographic regions prioritized for further collection of landrace groups for ex situ conservation include South Asia, the Mediterranean and West Asia, Mesoamerica, sub-Saharan Africa, the Andean mountains of South America and Central to East Asia. With further progress to fill these gaps, a high degree of representation of landrace group diversity in genebanks is feasible globally, thus fulfilling international targets for their ex situ conservation. ispartof: NATURE PLANTS vol:8 issue:5 pages:491-+ ispartof: location:England status: published

The International Potato Center (CIP) in Lima, Peru, maintains the global in-trust collection of cultivated potato. The material from this collection is distributed worldwide on request for research, breeding, and education under the auspices of the International Treaty for Plant Genetic Resources for Food and Agriculture (ITPGRFA, http://www.fao.org/plant-treaty/en/) (FAO 2009). The 4388 accessions in this collection are maintained in vitro to ensure that once cleaned of viruses, the germplasm remains virus free and can move freely across international borders without introducing disease(s) to other countries. While in vitro maintenance safeguards the material from infection, it requires a large number of resources to maintain an in vitro collection of this size. One way to reduce the cost of maintenance while still conserving the germplasm is to back up the collection in a cryobank. In fact, cryopreserved material could be the primary storage for some accessions that are genetically unique, but rarely requested. The shoot tips can be thawed from liquid nitrogen and regenerated into a plantlet when needed for research or distribution purposes. Cryopreservation protocols applicable to dozens of crops have been developed during the last two decades and many plant genetic research institutes have cryobanks that conserve hundreds or up to thousands of accessions (Pritchard 2016). However, throughput rates for large collections, quality standards, number of stored samples and repetitions, minimum viability criteria, inter-vial variation, backup storage strategies, and effective linkage with other genebank programs (for example, genetic identity testing) vary widely between species and cryobanks. These variables are often dependent on resources, staffing, and other priorities in the genebanks. At CIP, clear and strict quality standards were implemented in 2013, defining many of the characteristics described above (Vollmer et al. 2016). Despite this, the development of protocols applicable to large-scale cryopreservation of diverse collections, even within a single crop, can be a time-consuming, evolving, and a continuous process. The pioneers of potato cryopreservation published their first protocols about 35–40 yr ago (Bajaj 1978, 1981; Grout and Henshaw 1978; Towill 1981, 1983, 1984). Although the initial methods permitted successful cryopreservation of some potato genotypes, the development and adaptation of these protocols to high-throughput cryopreservation of diverse potato collections needed further refinement and simplification for routine use. Researchers at the Leibniz Institute DSMZ (German Collection of Microorganisms and Cell Cultures) refined the protocols in the mid-1990s, so a cryopreservation method could be successfully applied to hundreds of potato genotypes (Schafer-Menuhr et al. 1994, 1997). Recently, researchers have published other promising methods for potato cryopreservation, such as the D and V cryoplate. In these methods, shoot tips are “stuck” on special aluminum plates with uniform wells using sodium alginate to facilitate uniform sample handling, reduced risk of damage, and reduced loss of shoot tips (Yamamoto et al. 2015; Valle et al. 2017). At CIP, potato cryopreservation was initiated in the late 1990s (Golmirzaie and Panta 2000) by a protocol developed for Musa species (Panis et al. 2005) and the protocol has been continuously modified and improved (Panta et al. 2015; Vollmer et al. 2016). In 2013, CIP’s cryobank established a clear and strict quality management system (QMS), started to build a cryobank for the future with defined quality standards (Vollmer et al. 2016), and began actively adding on average 400 accessions per year into the cryobank. This paper describes the current status of CIP’s cryobank, analysis by potato species/subspecies (taxonomy based on Hawkes 1990), ploidy level, and country of origin to determine factors that affect the success rate, and the progress made over the last few yr. It also includes the results of a large-scale viability reassessment of 857 potato accessions, conserved for 1–2 yr in liquid nitrogen, and an assessment of the influence of the human factor on the survival and recovery rates of potato accessions cryopreserved with the droplet vitrification method (Sakai et al. 1990).

Conserving the genetic diversity of potato is critical for the long-term future of potato improvement programs. Further, it is the social and ethical responsibility of the present generation to ensure future generations have the same opportunities to use, exploit, and benefit from the genetic diversity that exists today. Genebanks and the ex situ conservation of potato genetic resources are the only way to ensure this happens; in situ conservation plays a complementary role, but it can never ensure that the vast diversity that exists on earth today is still there for use in the future. Material in ex situ genebanks not only serve as a reservoir of ready-to-use genetic material when needed but also provide invaluable tools for research now and in the future of cultivated potato and its wild relatives.

Breeders rely on genetic integrity of material from genebanks; however, admixture, mislabeling, and errors in original data can occur and be detrimental. Two hundred and fifty accessions, representing paired samples consisting of original mother plants and their in vitro counterparts from the cultivated potato collection at the International Potato Center (CIP) were fingerprinted using the Infinium 12K V2 Potato Array to confirm genetic identity of the accessions and evaluate genetic diversity of the potato collection. Diploid, triploid, and tetraploid accessions were included, representing seven cultivated potato taxa (based on Hawkes, 1990). Fingerprints between voucher mother plants maintained in the field and in vitro clones of the same accession were used to evaluate identity, relatedness, and ancestry using hierarchal clustering and model-based Bayesian admixture analyses. Generally, in vitro and field clones of the same accession grouped together; however, 11 (4.4%) accessions were mismatches genetically, and in some cases the SNP data revealed the identity of the mixed accession. SNP genotypes were used to assess genetic diversity and to evaluate inter- and intraspecific relationships along with determining population structure and hybrid origins. Phylogenetic analyses suggest that the triploids included in this study are genetically similar. Further, some genetic redundancies among individual accessions were also identified along with some putative misclassified accessions. Accessions generally clustered together based on taxonomic classification and ploidy level with some deviations. STRUCTURE analysis identified six populations with significant gene flow among the populations, as well as revealed hybrid taxa and accessions. Overall, the Infinium 12K V2 Potato Array proved useful in confirming identity and highlighting the diversity in this subset of the CIP collection, providing new insights into the accessions evaluated. This study provides a model for genetic identity of plant genetic resources collections as mistakes in conservation of these collections and in genebanks is a reality. For breeders and other users of these collections, confirmed identity is critical, as well as for quality management programs and to provide insights into the accessions evaluated.