The history of EWAC - The European Cereal Genetics Co-operative (Part II)
The meeting agreed that a joint effort should be initiated to develop monosomic series in 4 varieties that could be regarded as key varieties for West Europe, East and South-East Europe, Central Europe and Mediterranean Europe. Once developed the four new monosomic series would be used directly to locate agronomically important genes using the techniques of monosomic analysis pioneered by Sears (1953, 1954). The monosomic series would also be used to produce reciprocal intervarietal substitution series between each of the four key European varieties. It was also agreed that in each of the four key European regions additional monosomic series should be developed in locally adapted varieties. It was envisaged that the additional monosomic series could be compared to the regional key variety to link regional analysis with a wider European programme.
The development of monosomic series in the four key varieties was completed successfully and to the extent that two separate monosomic series were developed in Bezostaya 1 in Bulgaria and Romania and a series was developed in sister line Bezostaya 2 in Russia. Besides, the monosomic series developed in the key varieties an additional 38 monosomic series were developed in regionally adapted varieties from throughout Europe (Table 1).
The monosomic series were used directly in genetic analysis to locate a number of agronomically important genes influencing traits like disease resistance, plant height and flowering time. Initially the main method of analysis utilized was monosonic analysis in which a variety carrying a character of interest was crossed onto a monosomic series in a variety that carried an alternative allele for the character of interest. This method was used by Maystrenko to locate genes for vernalisation response Vrn-Al (formerly Vrn1) in Saratovskaya 29 and Saratovskaya 210 and to confirm the location of Vrn-DI (formerly Vrn3) on chromosome 5D of Chinese Spring (Maystrenko 1974). Later various new techniques were developed to improve the efficiency of using monosomics in the genetic analysis. These modifications included reciprocal monosomic analysis (McKewan and Kaltsike 1970) in which monosomics for the same chromosome are crossed reciprocally to permit the critical chromosomes of the two parental varieties to be compared individually against a similarly heterozygous background and backcross reciprocal monosomic analysis (Snape and Law 1980) which extends the use of the reciprocal monosomic analysis technique to varieties in which no monosomic series is available. This is achieved by the first crossing of a variety of interest onto available monosomics and then reciprocally crossing monosomic F1 progeny with the recipient monosomic. In EWAC the reciprocal monosomic technique was successfully used by Law et al., 1984 to study the 4D chromosome of Hobbit sib carrying the dwarfing gene Rht-BId (formerly Rht2) and the reciprocal backcross monosomic technique by Snape and Law (1980) to detect plant height differences associated with chromosome 5A from a range of European varieties.
The main aim for developing monosomic series was to utilise them as reciprocal backcross parents in the development of intervarietal chromosome substitution lines. The EWAC collaborative project to develop reciprocal substitution series between the 4 key EWAC varieties has, however, never been fully realised. In Cambridge, UK, chromosomes of varieties Bezostaya 1, Mara and Poros were successfully substituted into Cappelle-Desprez. Elsewhere the introduction of Bezostaya 1, Cappelle-Desprez and Mara chromosomes into Poros was commenced but halted at an early stage. No attempt was made to substitute chromosomes into Bezostaya 1 or Mara.
The substitution lines developed into a Cappelle-Desprez background
have proved extremely useful in genetic analysis and can only hint at
what might have been achieved if all reciprocal substitution lines had
been developed. The lines substituting Bezostaya 1 chromosomes into
Cappelle-Desprez have been widely used in studies to detect the chromosomal
location of agronomically important genes influencing characters such
as bread-making quality, disease resistance and plant height (Law and
Worland 1996). They have also been utilized in the detection of many
genetic, cytological and molecular markers.
Lines substituting individual chromosomes from the Italian variety Mara
into Cappelle-Desprez have been used in many collaborative EWAC studies
to locate and evaluate genes influencing plant height and adaptability.
A pair of linked genes Rht8 and Ppd-Dl (formerly Ppdl) located on the
short arm of chromosome 2D have been shown to be crucial to the adaptability
of Southern European wheats with Ppd-Dl promoting a yield increase of
at least 30% in Southern European environments (Worland and Law 1986;
Worland et al. 1996). Recent collaborative EWAC experimentation has
located a microsatellite molecular marker for Rht8. So, this important
dwarfing gene can be detected and studied in segregating populations
(Korzun et al 1998; Worland et al. 1998). Whilst the prime collaborative
experimental aims of EWAC have concerned intervarietal variation, many
of its active members have been studying alien genetic variation. Over
the past 30 years individual laboratories have developed a wealth of
alien genetic stocks adding or substituting alien chromosomes to the
bread wheat genome. Many of these stocks have been used to introduce
agronomically important genes from the aliens into wheat. In the spirit
of EWAC the alien genetic stocks have been freely exchanged amongst
members. In recent years new molecular staining techniques have opened
up new fields for precise studies of alien introductions and even for
precise analysis of the mechanisms of chromosome pairing (Reader et
al. 1997). Again, in the spirit of EWAC, training has been offered between
laboratories in the use of the new molecular cytogenetic techniques.