Brandenburg, W.A.

Oost, E.H.

Vooren, J.G., van de

van de Vooren, J.G.

NARCIS 

Taxonomic aspects of the germplasm conservation of cross-pollinated cultivated plants

Name not available

Wageningen Yield 

SEED REGENERATION 
IN CROSS-POLLINATED 
SPECIES 
Proceedings of the C.E.C. /EUCARPIA Seminar 
Nyborg/Denmark/15-17 July 1981 
Edited by 
E.PORCEDDU 
Istituto del Germoplasma, Bari, Italy 
GJENKINS 
Agricultural Research Council, London, UK 
OFFPRINT 
A.A.BALKEMA/ROTTERDAM 
Taxonomie aspects of the germplasm conservation 
of cross-pollinated cultivated plants 
W.A.BRANDENBURG, E.H.OOST & J.G.VAN DE VOOREN 
Agricultural University Wageningen, Netherlands 
ABSTRACT 
In Genetic Resources Centres (GRCs) documentation about accessions is 
standardised by means of descriptors, e.g. place of collection, morpho-
logical features, agricultural value. Botanical and/or fancy names are 
also considered to be descriptors. 
However, there is one essential condition for the usefulness of names 
as descriptors, namely the check on whether names are correct. If not 
regulated by the International Code of Botanical Nomenclature, 1978 (ICBN, 
1978), the nomenclature of cultivated plant3 is directed by the International 
Code of Nomenclature for Cultivated Plants, 1980 (ICNCP, 1980). 
For cultivars, including land races, however, ICNCP, 1980, does not 
contain rules concerning any typification. So, in these cases there is no 
well-defined connection between a plant material and its name. Particularly 
where it concerns the variation and the need for stability of cultivars 
of cross-pollinated plants, the lack of this connection is even wore 
striking. 
The rapidly increasing amount of accessions of cultivated plants in 
GRCs is one of the main reasons for focusing attention on this problem. 
This paper proposes a general procedure for checking cultivar names, 
based on living and conserved standards, descriptions and memory. The 
possible incorporation of the proposed procedure into a list of descriptors 
is discussed. 
NOMENCLATURE 
The International Code of Botanical Nomenclature, 1978 
(ICBN, 1978) regulates the nomenclature of plants by principles, 
rules and recommendations. For each rank, the notation of the 
Latin name of the corresponding taxon is ruled, e.g. by a fixed 
suffix. This means that it can be derived from the name, 
whether the taxon is a genus, a species or a botanical variety. 
Before a name is legitimised, the following conditions have to 
be fulfilled: 
- Latin diagnosis and description; 
- valid publication; 
- designation of a type. 
C.E.C. /EUCARPIA Seminar/Nyborg /July 1981 3 3 
By the principle of priority the ICBN governs which of 
the legitimate names is correct for the same taxon. In cases 
of homonymy, the same principle guides the decision as to how 
a legitimate name has to be correctly applied. 
By the type method, the connection between plant material 
and its name is made. The type of a genus is a species which 
is designated as such by the author. In other words, the type 
species always belongs to the genus to which it is assigned. 
In the case of a species or a taxon of lower rank, the type is 
a well conserved specimen, or, when this is not available, an 
illustration. Type, diagnosis, and full description, illus-
trations included, form the protologue, the starting point for 
a definitive identification of plant material. If not regulated 
by the ICBN, the nomenclature of cultivated plants is directed 
by the International Code of Nomenclature for Cultivated Plants, 
1980 (ICNCP, 1980). In the latter Code, the cultivar (culti-
vated variety) has been defined in Article 10 as follows: 
"The international term cultivar denotes an 
assemblage of cultivated plants which is clearly 
distinguished by any characters (morphological, 
physiological, cytological, chemical, or others) 
and which, when reproduced (sexually or asexually) 
retains its distinguishing characters." 
Dependent on mode of reproduction, the following cate-
gories of cultivars can be distinguished: 
- Vegetatively propagated - clone 
multlclone, mixture of closely 
resembling clones 
- Generatively propagated - line 
multiline, mixture of closely 
resembling lines 
- F1 hybrid 
- entity of cross-pollinated plants 
Comparing both definitions of cultivar and land race, it 
should be apparent that according to the ICNCP a land race has 
to be considered as a cultivar (Harlan, 1975). Consequently, 
the nomenclature of a land race is also directed by the ICNCP: 
34 
After 1st January, 1959 only fancy names within brackets 
or after the abbreviation cv. are admitted. Latin names, 
given before this date and derived from botanical varie-
ties, are also admissible. The cultivar name is placed 
after the botanical name of the taxon with the lowest 
possible rank. 
Translated synonyms in other common languages than the 
original are allowed. 
Later homonyms, generally accepted and widely used, are 
preferred to original names, which are afterwards re-
discovered. 
As to the cultivars, the ICNCP does not rule any typific-
ation. In order to be legitimate, the ICNCP states that a 
cultivar name has to be validly published. Names given before 
1st January, 1959 which have not been validly published, can 
be legitimised by a registration authority. The publication 
and registration list must contain a description of the 
cultivar. 
Cultivars are often adapted to a small range of environ-
ments. The expression especially of quantitative characters is 
greatly influenced by locality and time. Although quantitative 
characters (for example yield and earliness) are often of great 
economic importance, they have a restricted descriptive value 
for the above mentioned reason. For an adequate description it 
is useful to look for qualitative characters, which do not 
necessarily have to be of economic importance. 
Cultivars do not form a closed classification as in 
botanical classification under the ICBN (Figure 1). Between 
cultivars of the same botanical taxon certain gaps, containing 
non-cultivated plants, can exist (Figure 2). Consequently, not 
only description, but circumscription, based on any represent-
ative element, should be considered essential. 
In connecting a cultivar with its name, the type method 
in the conception of the ICBN cannot be applied for the follow-
ing reasons: 
A type does not necessarily have to be a representative 
element. 
A type of any living plant material cannot exist. 
35 
SUBSP. 
1 
! IK! 
i L- i 
i — 
i 
iFi ! 
•
 J1 
— , 
VAR. 
i 1 © 
S P E C I E S 
Fig. 1. Closed classification under 
the ICBN. Hierarchical 
order of ranks. 
S P E C I E S 
Fig. 2. Open classification of 
cultivars, independent of 
botanical classification. 
Instead of a type, we strongly recommend using a living 
and conserved standard, both consisting of a representative 
sample of the cultivar. The mean and variation of characters 
within a cultivar are fixed by these standards. A living 
standard is important, because of its independence of locality 
and time. Being sampled once, a conserved standard is deter-
mined by the then prevalent environmental factors. Therefore, 
it is less useful than the living standard. However, it is 
valuable for a longer term, in case the living standard is 
absent or lost. By using both standards, a reliable connection 
between the cultivar and its name can be made. 
TAXONOMY AND GERMPLASM OF CROSS-POLLINATED PLANTS 
The aim of Genetic Resources Centres (GRCs) is to con-
serve as wide as possible a range of genetic diversity, with 
potential agricultural value. At present, among all the 
accessions of GRCs, cultivars, including land races, are the 
most frequent items (Ayad et al., 1980). 
There are two main reasons for conserving germplasm by 
means of cultivars. Firstly, cultivars representing certain 
combinations of characters are entities that have already 
proved their usefulness in agriculture. So, asking for culti-
vars, plant breeders will find the desired genes in a more or 
36 
less balanced genetic background, formed under the process of 
domestication and breeding. Secondly, a cultivar is indicated 
by a name. This name forms an entry in all documentation about 
the cultivar. In the case of old cultivars, one can trace back 
original descriptions or illustrations and even make use of 
oral tradition. The documentation on cultivars acquired in 
this way can be used for definitive identification of an 
accession. Likewise, if additional knowledge about origin, 
special characters and (historical) use etc. is obtained, this 
can be of great importance to plant breeders and crop 
evolutionists. 
In cross-pollinated plants, there are obvious advantages 
in conserving especially old cultivars, provided that they can 
be obtained in sufficiently large quantities of seeds. Because 
these cultivars are sufficiently heterogeneous, thus securing 
conservation of genetic diversity, the number of accessions 
can be restricted. Consequently, more time per accession 
becomes available to complete the documentation of each 
accession. 
PROCEDURES TO CHECK THE IDENTIFICATION OF ACCESSIONS 
In GRCs, documentation on accessions is standardised by 
means of descriptors, e.g. place of collection, morphological 
features, agricultural value (Seidewitz, 1973, 1979). Botanical 
names as well as cultivar names are also considered to be 
descriptors, because they supply intrinsic information about 
the plant material concerned. 
There is, however, one essential condition for the use-
fulness of names as descriptors, namely the check whether names 
are correct. Botanical names, regulated by the ICBN, can be 
checked by comparing with the protologue. If an accession has 
been found to be correctly named, a symbol can be added behind 
the name, as is done in the seed indexes of botanic gardens. 
Cultivar names, regulated by the ICNCP, cannot be veri-
fied by studying protologues. However, the check whether 
cultivar names have been correctly applied is made possible by 
living and conserved standards, descriptions and memory. 
A living standard has to be sampled from the original 
37 
plant material. With regard to old cultivars, a sample has to 
be taken from the accession at the time of introduction. With 
regard to modern cultivars, a living standard has to be sampled 
preferably from the original plant material, grown at the 
winner's nursery. This is already done in several cases by 
registration authorities. 
The same holds for conserved standards. They should 
consist of herbarium specimens, colour photographs, colour 
slides and preparations. 
By description, the oldest, validly published description 
is meant, irrespective of the acceptance of the cultivar by a 
registration authority. 
The memory of experts is sometimes the only way to iden-
tify an accession as a named cultivar. 
The variation of cross-pollinated plants necessitates 
living and conserved standards, containing enough variation to 
circumscribe a certain cultivar and to distinguish it from 
other similar cultivars. In comparison with living standards, 
the rate and nature of drift and contamination can be deter-
mined after regeneration. Both phenomena may cause the shift 
of frequencies of characters in such a way, that an accession 
no longer resembles the original cultivar. In the long run 
accessions can only be compared with conserved standards, 
because living standards have a restricted size and lifetime. 
Consequently, determination of drift and contamination will 
then be impeded. 
Apart from comparing with standards, accessions can be 
checked on original descriptions. In some cases, however, 
descriptions, especially of old cultivars, cannot be used 
because they are either non-existent or incomplete. Then it 
will be necessary to base identification on the expert's ex-
perience. It is obvious that this is less desirable since it 
is the most subjective identification. 
The results of these four procedures can be used as 
descriptor states. Incorporation can be done by adding a four 
digit code to the descriptor 'cultivar name' (Figure 3). A 
positive check on each of these procedures will give the corres-
ponding digit; a negative check the digit '0'. 
38 
During each regeneration of an accession every precaution 
should be taken to preserve its integrity. A sample of the 
regenerated accession has to be checked again with the four 
procedures on characters with descriptive value. If, for 
instance, the accession no longer corresponds to the living 
standard, the code 0-2-3-4 has to be added to the cultivar 
name, as can be seen from Figure 4. Changes in the four digit 
code must be added as soon as possible to the descriptor 
'cultivar name'. 
Accession 
name • 1.2.3.4 
I.hing standard n e g a t i v e check 
name • 0 .0 .0 .0 
Conserved standard positive check 
name • 0.2.0.0 
Description positive check 
name » 0 .2 .3 -0 
Mimorv positive . check 
t 
name • 0.2.3.4 
Accession: name0.2.3 4 
t 
storage with new code 
Fig. 4. Procedures to check 
regenerated accessions. 
In this example the 
accession will be recoded. 
Living standard 
Conserved standard 
Description 
Memory 
Accession 
name • 0 .0 .0 .0 
positive check 
name • 1 .0 .0 .0 
positive check 
name • 1.2.0.0 
positive check 
name » 1 . 2 . 3 . 0 
positive , check 
name • 1.2.3.4 
t 
Accession: name 1.2.3.4 
Fig. 3. Procedures to check the 
i d e n t i f i c a t i o n of 
access ions . 
DISCUSSION 
According to Hyland (1970), the controlled use of wild 
or cultivated plant germplasm is largely dependent on accurate 
description and taxonomie identification. Taxonomically well-
identified accessions will obviously provide us with important 
data. Exchange of accessions will be facilitated by good, 
standardised documentation (Seidewitz, 1973/ 1979; Erskine and 
Williams, 1980). As duplicates can be avoided, and regener-
ation especially of cross-pollinated plants is very laborious, 
a restricted number of well-documented accessions will be 
favourable, avoiding the necessity of pooling more or less 
similar accessions into 'race reservoirs'. A 'race reservoir' 
39 
will end up as an amorphous mass without the opportunity to 
maintain interesting, special properties of single accessions 
(Marshall and Brown, 1975; Burton, 1979). In the case, how-
ever, of several poorly documented similar accessions, based 
only on memory (code 0-0-0-4), pooling them will be justi-
fied. 
The proposed method will provide every user of GRC « 
accessions with information about the present status of the 
name. A well connected name will supply entries in all docu-
mentation of the accession concerned, and will facilitate 
international communication. 
ACKNOWLEDGEMENTS 
The authors wish to express their appreciation to 
Dr. A.C. Zeven for his helpful remarks and to Mr. J.S. de Block, 
who kindly corrected the English manuscript. 
REFERENCES 
Ayad, G., T o l l , J . , and Esquinas-Alcazar , J . T . , 1980. Di rec tory of germ-
plasm c o l l e c t i o n s I I I Cereals 2 . Maize. I n t e r n a t i o n a l Board for 
P l a n t Genetic Resources, Rome. 
Burton, G.W., 1979. Handling c r o s s - p o l l i n a t e d germplasm e f f i c i e n t l y . Crop 
Science , 19_, 685-690. 
Er sk ine , W. and Wil l iams, J . T . , 1980. The p r i n c i p l e s , problems and r e s -
p o n s i b i l i t i e s of the p re l iminary eva lua t ion of gene t ic resources 
samples of seed-propagated c r o p s . PGR Newsl . , 4 1 , 19-33 . 
Harlan, J . R . , 1975. Crops and man. American Society of Agronomy. Crop 
Science Socie ty of America, Madison, Wisconsin, p . 138, 163 . 
Hyland, H.L. , 1970. Desc r ip t ion and eva lua t ion of w i ld and p r i m i t i v e 
in t roduced p l a n t s . I n : O.H. Frankel and J .H. Bennett ( e d s . ) . 
Genetic Resources i n P l a n t s , 413-419. IBP Handbook no. 1 1 . Blackwell 
S c i e n t i f i c P u b l i c a t i o n s , Oxford and Edinburgh. 
I n t e r n a t i o n a l Code of Botanica l Nomenclature, 1978, adopted by the Twelfth 
I n t e r n a t i o n a l Botanica l Congress, Leningrad, Ju ly 1975. F.A. S t a f l e u 
e s . ( e d . ) . Regnum Vegetabi le v o l . 9 7 . Bohn, Scheltema and Holkema, 
U t r ech t . 
I n t e r n a t i o n a l Code of Nomenclature for C u l t i v a t e d P l a n t s , 1980, formulated 
and adopted by the I n t e r n a t i o n a l Commission for the Nomenclature of 
C u l t i v a t e d P l a n t s of the I . U . B . S . , C D . B r i c k e l l e s . ( e d . ) . Regnum 
Vegetabi le v o l . 104. Bohn, Scheltema and Holkema, U t r e c h t . 
Dr. W. Junk BV, P u b l . , The Hague. 
Marsha l l , D.R. and Brown, A.H.D., 1975. Optimum sampling s t r a t e g i e s i n 
gene t i c conse rva t ion . I n : O.H. Frankel and J .G. Hawkes ( e d s . ) . 
Crop gene t i c resources for today and tomorrow, 123-127. Cambridge 
Univers i ty P r e s s , Cambridge, London, New York and Melbourne. 
Se idewi tz , L . , 1973. Thesaurus for the i n t e r n a t i o n a l s t a n d a r d i s a t i o n of 
genebank documentat ion. I n s t i t u t für Pflanzenbau and Saatgutforschung 
der Forschungsans ta l t für Landwir t schaf t , Braunschweig-völkenrode. 
40 
Seidewitz, L., 1979. Need for a standardised information system. PGR 
Newsl., 39, 11-12. 
DISCUSSION 
Henny Roelefsen (Netherlands) I would like to know more about 
the four digit code you mentioned. Is it meant for computer 
administration? 
W.A. Brandenburg (Netherlands) Yes, it is possible to incor-
porate it in a computerised system but I am not a computer 
specialist. To have such a code adds the descriptor cultivar 
name so you have the name of the accession, and the present 
status of the name will be given in the code. For instance, 
for a good cultivar which is clearly documented, you can have 
the code 1-2-3-4, there is a living standard, there is a con-
served standard, there is a good description and there are 
enough people who know the accession or the cultivar. Then you 
have a complete code. However, if after three or four regen-
erations the living standard is lost because you cannot 
regenerate the seeds of these living standards, then you have 
to say the present status of your cultivar name is 0-2-3-4. 
This will prevent names going on and on in cases where the 
material is not the same as the original. That is the meaning 
of this code. 
Henny Roelofsen So there is no reference to the documentation 
material in it, the code only establishes whether or not it 
exists? 
W.A. Brandenburg Yes, it is an administrative code. 
41 


Taxonomic aspects of the germplasm conservation of cross-pollinated cultivated plants

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Wageningen Yield