A Database for Triticeae and Avena
II.10. Three chemical races in barley.
Sune Fröst, Institute of genetics, University of Lund, S-223 62
Employing thin-layer chromatography, 266 land, or local, varieties of
barley have been investigated as to the presence or absence of phenolic
compounds. Strong varietal differences have been demonstrated as regards
the occurrence of flavonoids in the leaves. It has been possible to discriminate
three distinct patterns, or physiological races, which we call A, B and
C (Fröst and Holm, 1971, 1972, 1973; Fröst and Asker, 1973).
The following method is used. The flag leaf is excised from three plants
of each variety and dried at 40°C. The leaves are crushed and extracted
in methanol containing 1% concentrated HCl by volume. From each extract,
15 mul is applied at the starting point of a 15 x 15 cm chromatographic
plate coated with cellulose powder emulsion. Both one and two-way separations
are employed. In two-way chromatography the solvent for the first direction
is n-butanol: acetic acid: water (3:1:1 by volume) and for the second direction,
2% aqueous formic acid. About 50 spots appear in the two-way separation,
and the A pattern is distinguished from the B pattern by the absence of
two large, intensively yellow-green spots. The C pattern differs
from the B pattern by the absence of one of the large spots. For one-way
separation, 2% aqueous formic acid is often used, which gives distinct
differences between the three races in barley (see Figure 1). This weak
acid solution permits differentiation of glycosides.
Figure 1. One-way separation showing sharp differences
between the three different races (A, B, and C) in barley.
It is of interest that of 266 investigated varieties of diploid spring
barley I have obtained the same three very striking chemical races of barley,
which occur throughout its cultivation area, and which is evident from
Table 1. The geographical distribution of the three
flavonoid patterns in barley.
From Table 1 it can be seen that the varieties that were obtained from
Ethiopia were almost exclusively of the C type. Thus of 58 investigated
Ethiopian barley varieties, 53 varieties displayed the C pattern. One can
already on this basis confirm that the Ethiopian varieties form a racial
centre. With the aid of these results, it can be tempting to compare existing
theories regarding the phylogeny of barley. Ethiopia is generally considered
to be one of three conceivable centres of origin. With respect to the Ethiopian
material, it should be pointed out that the convarieties deficiens
and labile originate or occur only in Ethiopia including Erytrea.
However, Ethiopia is considered to be a secondary centre. As regards the
remaining data, one can compare the results from India and Afghanistan
with varieties from Turkey and Syria. There are significant differences.
The Indian and Afghanistan material includes a very large number of varieties
that exhibit the B pattern, whereas the barley varieties from Turkey and
Syria are dominated by the A pattern. The dominance of the B pattern in
the varieties from India and Pakistan is conspicuous if all the investigated
varieties from the various parts of the world are compared. As it can be
seen, the A pattern is dominant. Of 266 investigated varieties only 56
were of the B type. If Ethiopia is excluded, the number of varieties from
the other possible gene centres, namely, Southeast Asia, China, Japan and
Tibet, on the one hand, and Asia Minor, on the other, is still too few
to be able to draw any conclusions. The barley varieties that were investigated
from the different European countries, North and South America and northern
and southern Africa show that no deviating patterns or races occur. The
results thus establish that only these three patterns apparently occur
and that they have a very large geographical distribution.
The first person to postulate that barley has different gene centres,
which has been summarily discussed here, was Vavilov. He believed that
there were three gene centres--primary and secondary ones. These theories
are based on morphological studies. These putative gene centres have been
discussed by a number of researchers and guided by these discussions the
origin of barley has also been approached.
If the three chemical races of barley are relevant as regards the phylogenetic
hypotheses, then, the continued investigation of flavonoids may well provide
corroborative evidence. However, it is probable that different ecological
requirements in the different areas or "centres" have resulted in this
selection in the flavonoid patterns in barley.
From the biochemical point of view, the A pattern should be the primary
one, whereas the B and C patterns are secondary or mutant types. More enzymes
are required to produce additional compounds (flavonoids). Perhaps one
may entertain that the A pattern is the most primitive or original one.
Chemical analyses of the flavonoids contained in leaves of barley have
been made by Seikel et al. (1962). They found that saponarin, as well as
lutonarin 3' - methyl ether, was present in large amounts in the leaves
in all the genotypes that they investigated. One the other hand, they found
lutonarian (isoorientin 4' -O- glycoside) only in certain genotypes of
6-week-old plants, and then in the same copious amounts as saponarin. It
is tempting to assume that lutonarin is one of the compounds that evokes
the differences between the A, B and C patterns.
Controlled crosses have been carried out on a limited scale between
different barley races: viz. A x B, Bx A, A x C and C x A. Analyses of
the F1 plants did not disclose any differences between the reciprocal crosses.
There was complete dominance of the B and C patterns.
At the present time, I am working with about 1,500 land varieties of
barley, which were collected at the Swedish Seed Association in Svalöf.
After I have completed the chromatographic investigation of them, as
well as of other barley species (Hordeum spontaneum, H. acriocrithon),
it should be possible to give more conclusive information about the significance
of the three flavonoid patterns in barley.
Fröst, S. and G. Holm. 1971. Thin-layer chromatographic studies
of compounds in twenty varieties of barley. Hereditas 69:25-34.
Fröst, S. and G. Holm. 1972. Thin-layer chromatographic studies
of phenolic compounds in seventeen parental varieties of barley. Hereditas
Fröst, S. and G. Holm. 1973. A new phylogenetic approach in barley.
Hereditas (in press).
Fröst, S. S. Asker. 1973. Further studies of flavonoid patterns
in barley. Hereditas (in press).
Seikel, M., A. Bushnell, and R. Birzgalis. 1962. The flavonoid constituents
of barley (Hordeum vulgare). III. Lutonarin and its 3' - methyl
ether. Arch. Biochem. Biophys. 99:451-457.
BGN 4 toc
BGN Main Index