As in many other crop species, also in Allium crops genetic erosion is taking place. In this mini review the current global state of the art is presented on Allium ex situ genetic resources and more in particular on onion genetic resources. Furthermore future possible actions are indicated to preserve the Allium genepool in a more effective way, amongst which a proposal to develop an Allium genetic resources internet sit

Kik, C.

English

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 135
Allium Genetic Resources with Particular Reference to Onion 
 
C. Kik  
Centre for Genetic Resources, the Netherlands (CGN) 
Bornsesteeg 65  
6708 PD Wageningen  
The Netherlands  
 
Keywords: Allium cepa, onion, genetic resources, wild relatives, genetic erosion 
 
Abstract 
As in many other crop species, also in Allium crops genetic erosion is taking 
place. In this mini review the current global state of the art is presented on Allium ex 
situ genetic resources and more in particular on onion genetic resources. Furthermore 
future possible actions are indicated to preserve the Allium genepool in a more effec-
tive way, amongst which a proposal to develop an Allium genetic resources internet 
site. 
 
INTRODUCTION 
The availability of genetic variation within crops, present in ex situ and in situ 
collections, is of pivotal importance for a sustainable agriculture, even in the era of X-
omics. However, since the beginning of the 20th century genetic erosion of crops has 
become increasingly a reality in many crop species (Pistorius, 1997). Genetic erosion can 
take place on several levels: a) on the crop level: decrease of genetic variation can take 
place due to the use of more uniform and highly productive cultivars which replace in a 
continuous pace old landraces; b) on the habitat level: the loss of habitats can be very 
detrimental for the survival of crop wild relatives; and c) on the knowledge level: losses 
on this level can mean that crops are forgotten or even can get lost. In this review paper I 
will be dealing primarily with the crop and habitat level as the erosion on the knowledge 
level for edible Allium crops is most probably not large. 
 
HISTORY OF ALLIUM PGR 
In the first large overview on onions and related crops (Jones and Mann, 1963), 
the topic of Allium genetic resources is not mentioned. Astley et al. (1982) were the first 
that made an overview of global edible Allium genetic resources. They identified major 
Allium collections worldwide, and presented the numbers of accessions per species per 
collection. Furthermore a draft Allium descriptor list was included in their report together 
with a list of collecting priorities. In total ca. 9000 accessions were reported to be present 
worldwide and the number of onion accessions was by ca. 7000 by far the largest. The 
collection of local/modern cultivars and landraces of Allium cepa (dry bulb onions and 
shallots) was considered as an important future collection priority as modern F1 hybrids 
were thought to quickly replace old landraces. A decade later, Astley (1990) described 
Allium ex situ conservation by focusing on characterization, evaluation, documentation 
and utilization of collections. Also he indicated that wild Allium taxa are seriously 
underrepresented in global collections and that species’ distribution areas are not 
adequately covered. Last but not least, Cross (1998) suggested that the cultivated Allium 
species are well collected, however collections from the centers of biodiversity of Allium 
are poor and therefore the variation sampled until present might be inadequate. 
  
PRESENT SITUATION ON ALLIUM PGR 
Currently around 27,000 Allium accessions are held in genebanks worldwide 
(www.ipgri.cgiar.org/germplasm/dbintro.htm). However, one must consider this number 
with caution as not all genebanks have uploaded their accessions to the aforementioned 
database. Furthermore, the percentage of duplications within and between Allium 
collections is unknown, misclassification is not accounted for and also availability of 
Proc. XXVII IHC - Cultiv. Utiliz. Asian, Sub-Trop., Underutilized Hort. Crops 
Eds.-in-Chief: Dae-Geun Oh and Chieri Kubota 
Acta Hort. 770, ISHS 2008 
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accessions is unclear in many cases. Especially the percentage of duplication can be of 
influence on the total number of accessions. In this respect Van Hintum and Boukema 
(1999) showed for lettuce that around 60% of the accessions were duplicated among the 
collections of the major collection holders. In table 1, the number of Allium accessions is 
shown that are present in global collections: onion (A. cepa) is represented most, followed 
by garlic (A. sativum) and leek (A. porrum). It could be argued that for these three species 
less collection efforts should be carried out, however one should be careful in this respect 
in view of the duplications and misclassifications that can occur in worldwide genebanks. 
For all the other 750 Allium species (Gregory et al., 1998), next to onion, garlic and leek, 
genetic resources are certainly not sufficient and collection missions or in situ 
conservation actions are needed, because wild relatives are important for the development 
of better cultivars (Kik, 2002). 
 
PRESENT SITUATION ON ONION PGR  
As has already been mentioned previously the onion germplasm has been sampled 
most extensively when compared to the other species within the genus Allium. 
Concerning the various onion genepools, Van Raamsdonk et al. (2003) reviewed the 
existing literature and found that only a few species can be crossed directly with onion, 
namely A. cepa, A. vavilovii, A. galanthum and A. roylei. These species can be considered 
as species from the primary genepool of onion. The secondary genepool is at least 
composed of A. fistulosum and its progenitor A. altaicum, as Khrustaleva and Kik (2000) 
showed that A. roylei can act as a bridging species between onion and A. fistulosum/A. 
altaicum. The tertiary genepool consists of A. pskemense and A. oschaninii and another 
20 species from the subgenera Cepa, Reticulatabulbosa, Polyprason and Anguinum 
(phylogeny according to Friesen et al., 2005; Table 2) or another 220 species (phylogeny 
according to Hanelt et al., 1990; Table 2).  
In Table 3 an overview is given of the number of accessions per species present in 
the different onion genepools. From this table it can be concluded that although the onion 
germplasm is reasonably available, the germplasm of its wild relatives is only scarcely 
represented in worldwide genebanks. It is clear that collection missions or in situ conser-
vation measures should be carried out to safeguard these important genetic resources. 
This is even more true as from literature as it is known that these resources are under 
severe threat in their natural conditions (area delimited in the west by the Pamir Altai and 
in the east by the Tien Shan mountain range) due to human activities (Fritsch and Friesen, 
2002).  
 
FUTURE ACTIVITIES IN ALLIUM PGR 
In general it can be stated that for future activities in the area of Allium genetic 
resources, serious conservation efforts should be undertaken as parts of the genus are 
under threat. This is especially true for onion and its wild relatives but also for garlic 
(Kamenetsky et al., 2005). In this context it would be important to develop an internet 
platform for Allium species in which the global ex situ genetic resources are indicated and 
also the global in situ initiatives. In this way the status of the Allium PGR can be 
monitored in a more efficient way. Furthermore it would be desirable to determine the 
amount of duplications in Allium ex situ collections worldwide as this might prove to be a 
serious problem. Also the identification of the primary, secondary and tertiary genepools, 
for important Allium crop species like onion, leek and garlic, would be of great help for 
the ongoing breeding research in these crops. Last but not least characterization and 
evaluation of Allium accessions would be of importance for the utilization of the 
germplasm. 
 
Literature Cited 
Astley, D., Innes, N.L. and Van der Meer, Q.P. 1982. Genetic Resources of Allium species, 
IBPGR secretariat, Rome, Italy p.38. 
Astley, D. 1990. Conservation of genetic resources. p.177-198. In: H.D. Rabinowitch and 
 137
J.L. Brewster (eds.), Onions and Allied Crops, CRC Press Inc, Boca Raton, Florida, 
USA Vol. I. 
Cross, R.J. 1998. Review paper: global genetic resources of vegetables. Plant Varieties 
and Seeds 11:39-60. 
Friesen, N., Fritsch, R.M. and Blattner, F.R. 2005. Phylogeny and new intrageneric classi-
fication of Allium L. (Alliaceae) based on nuclear ribosomal DNA ITS sequences. 
Aliso 22:372-395. 
Fritsch, R.M. and Friesen, N. 2002. Evolution, domestication and taxonomy. p.5-30. In: 
H.D. Rabinowitch and L. Currah (eds.), Allium Crop Science: Recent Advances, 
CABI Publ., Wallingford, UK. 
Gregory, M., Fritsch, R.M., Friesen, N.W., Khassanov, F.O. and McNeal, D.W. 1998. 
Nomenclator Alliorum. Whitstable Litho Printers Ltd., Whitstable, Kent, UK p.83. 
Hanelt, P. 1990. Taxonomy, Evolution and History. p.1-26. In: H.D. Rabinowitch and J.L. 
Brewster (eds.), Onions and Allied Crops, CRC Press Inc, Boca Raton, Florida, USA. 
Jones, H.A. and Mann, L.K. 1963. Onions and their Allies, Leonard Hill Ltd, London 
p.286. 
Kamenetsky, R., London Shafir, I., Khassanov, F., Kik, C., Van Heusden, A.W., Vrielink-
van Ginkel, M., Burger-Meijer, K., Auger, J., Arnault, I. and Rabinowitch, H.D. 2005. 
Diversity in fertility potential and organo-sulphur compounds among garlics from 
Central Asia. Biodiversity and Conservation 14:281-295. 
Khrustaleva, L.I. and Kik, C. 2000. Introgression of Allium fistulosum into A. cepa 
mediated by A. roylei. Theor. Appl. Genet. 100:17-26. 
Kik, C. 2002. Exploitation of wild relatives for the breeding of cultivated Allium species. 
p.81-100. In: H.D. Rabinowitch and L. Currah (eds.), Allium Crop Science: Recent 
Advances, CABI Publ., Wallingford, UK. 
Pistorius, R. 1997. Scientists, plants and politics, A History of the Plant Genetic 
Resources Movement, IPGRI, Rome, Italy p.134. 
Van Hintum, Th.J.L. and Boukema, I. 1999. Genetic resources of leafy vegetables. p.59-
72. In: A. Lebeda and E. Kristkova (eds.),  Eucarpia Leafy Vegetables ’99, Palacky 
University, Olomouc, Czech Republic.  
Van Raamsdonk, L.W.D., Ensink, W., Van Heusden, A.W., Vrielink-van Ginkel, M. and 
Kik, C. 2003. Biodiversity assessment based on cpDNA and crossability analysis in 
selected species of Allium subgenus Rhizirideum. Theor. Appl. Genet. 107:1048-1058.  
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Tables 
 
 
 
Table 1. Number of accessions per species and occurrence (%) of species in worldwide 
Allium collections (source: www.ipgri.cgiar.org/ germplasm/dbintro.htm). 
 
 
Allium species No. of accessions % 
cepa 12740 46.7 
sativum 4560 16.7 
porrum 2148 7.9 
fistulosum 951 3.5 
tuberosum 434 1.6 
schoenoprasum 274 1.0 
nutans 95 0.3 
chinense 27 0.1 
wild relatives 6073 22.2 
TOTAL 27302 100.0 
 
 
 
Table 2. Number of species present in subgenus Rhizirideum (sensu Hanelt, 1990), and 
the number of species/accessions present in genebanks worldwide. In the parentheses 
very rarely sampled species are indicated.  
 
 
Subgenus  
(sensu Friesen) 
No. of species/subgenus No. of species in 
genebanks 
No. of accessions in 
genebanks 
Cepa 22 (8) 18 (2) 14641 
Reticulatabulbosa 55 (18) 34 (6) 393 
Polyprason 61 (14) 29 (5) 252 
Rhizirideum 20 (11) 19 (1) 681 
Butomissa 4 3 615 
Anguinum 5 (5) 4 (2) 56 
Cyatophora 3 (1) 2 75 
 TOTAL 170 (57) 109 (16) 16723 
 
 
 
Table 3. The onion genepools; number of accessions based on the IPGRI database 
(source:www.ipgri.cgiar.org/ germplasm/ dbintro.htm). 
 
 
Genepools No. of accessions 
Primary 
A. cepa 12740 
A. vavilovii 20 
A. galanthum 34 
A. roylei 4 
Secondary 
A. fistulosum 951 
A. altaicum 121 
Tertiary 
A. pskemense 21 
A. oschaninii 41  


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