A Database for Triticeae and Avena
Konishi and Matsuura (1988) found that the Ga2 gene for certation
is linked with the complex locus (Estl, Est2, and Est4) for esterase
isozymes which are located on a terminal portion on the long arm of
chromosome 3 (recombination value = 11.7 ± 4.1%). The present authors
aimed to examine geographical distribution of the Ga2 gene, using F2
populations crossed between 171 varieties collected from different
regions of the Old World and an Afghan variety, 487, as the common
parent for topcrosses. For finding the varieties having the Ga2 gene,
100 F2 seedlings of each cross were grown under a 12 h illumination in a
growth cabinet kept at 180C for 10 days, and the crude extract from the
first leaf of the individual was electrophoresed to examine the genotype
for esterase isozymes. In each of the F2 populations, the genotypes of
individuals were easily detected by banding patterns of esterase
isozymes, and classified into three groups, namely, those of the parent
tested (P1), the common parent 487 (P2) and their heterozygote (F1).
When the certation did not occur, segregation of genotypes for esterase
isozymes (P1:F1:P2) was compared to a ratio of 1:2:1.
Relationship between frequencies of P1 and P2 genotypes in F2
populations is indicated in Fig. 1. When the frequency of P1 genotype
increased more than 25% and that Of P2 genotype decreased significantly,
the variety tested (P1) was thought to have the Ga2 gene, shown as a black
circle. Meanwhile, the open circles indicate that the certation did not
occur in these F2 populations, scattering around the cross point of
theoretical frequencies of 25%.
As is apparent in Table 1, 16 (9.4%) of 171 varieties tested possess
the Ga2 gene for certation, and are found in Asia, mainly in Japan and
Nepal. It is noteworthy that almost all these Japanese varieties are
distributed in the southern parts of Japan, and all of the Nepalese
varieties possessing the Ga2 gene are naked ones, with only one
exceptional covered barley.
The result suggests that the skewness of segregation for marker
genes located near the terminal of the long arm of chromosome 3 might be
observed in hybrid populations crossed with Asian varieties having the
Ga2 gene. Furthermore, the common parent 487 is thought to be a suitable
one to examine the varieties having the Ga2 gene, because its genotype
for esterase isozymes is rare pong the barley varieties, composing of
three alleles of Est11A, Est2null, and Est4null .
Konishi, T. and S. Matsuura. 1988. A new certation gene, Ga2 on the
long arm of chromosome 3 in barley. BGN 18:33-36.