A Database for Triticeae and Avena
A two-rowed, covered barley variety, Malatya 5, collected in Turkey
by Kyoto University Hindu-Kush Expedition, is characterized by extremely
dense or compact spike and short stem. Mode of inheritance of the
extremely dense spike character was investigated using a cross between
Malatya 5 and Hayakiso 2 (Japan) which was known to have a dense spike
gene, l on chromosome 1.
Frequency distribution in the F2 of length of rachis internode
(Fig. 1) revealed a clear tetra-modal curve, and the four groups of
plants could easily be classified; (A) having further compact spike than
that of Malatya 5, (B) having the same extremely spike as Malatya 5, (C)
having ordinarily dense spike as Hayakiso 2, and (D) having lax spike.
The number of F2 plants belonging to the A, B, C, and D groups were
58, 84, 8, and 36, respectively, which fitted well to the segregation ratio
of 5:7:1:3 (Table 1). The result of F3 test indicated that eight F2
plants taken in the group C were all homozygous for Hayakiso genotype or
ordinarily dense spike, while 21 F2 plants taken from group D showed two
genotypic groups. Seven of 21 F2 plants were homozygous for the lax spike
genotype, and the other plants were heterozygous producing plants of both
Hayakiso and lax spike phenotype. Furthermore, the F3 lines which
segregated lax spike plants were not found in the F3 test of the group A.
These facts suggested that genotypic constitutions of parental varieties
and the F2 plants of four groups are as shown in Table 1, where dominant gene, D, tentatively named for extremely dense spike, and recessive gene
for dense spike on chromosome I are epistatic to the gene L and the gene d
for lax spikes, respectively.
The relation between spike density and stem length was studied
further. As seen in Fig. 2, stem length of the F2 plants varied
continuous between the parents values. Among the groups classified by
spike density, frequency distribution regarding stem length shifted more
or less toward longer stem in the order of groups A, B, and C+D.
Consequently mean value of each group was about 10 cm more than the
preceding group. The results suggested that, although stem length is
mainly controlled by polygenes in this cross, the gene or genes for spike
density also affect the stem length.
Furthermore, the results of an allelic test have indicated that
D is allelic to or identical with the dominant genes for extremely
dense spike involved in B.855 (USA) and Russian 31 (USSR).*
*Editor's note: The gene symbol D has been assigned to several other
morphological traits. Dr. U. Lunaqvist has suggested that an allelic
series, based on the gene symbol Zeo and the name zeocripton, be
established for the dominant dense spike mutants.