GrainGenes
A Database for Triticeae and Avena
Takahashi et al., p. 74
II.39 New find of an allele Rt' semi-dominant over rt for rattail spike.
R. Takahashi, J. Hayashi and I. Moriya, The Ohara Institute for Agricultural Biology, Okayama University, Kurashiki, Okayama-ken, Japan
The gene rt attracts our especial interest as it is a marker on the distal end of the short arm of chromosome 2. But, this is not necessarily a good marker, because that its phenotype is completely sterile and also that its character expression occurs at a very late stage of plant development.
We have incidentally found that a Japanese naked cultivar Okaiku 3 has a new allele semi-dominant over rt, which is tentatively denoted as Rt': A cross of this variety with a plant heterozygous for rattail gene (Rt/rt) gave two distinct types of F1 plants having respectively normal and intermediately deformed spikes in a ratio of about 1:1. A progeny test with these F1 plants has shown that, while all of the normal plants bred true, there appeared from the other F1's three types of plants having different spikes as shown in Fig. 1. This will doubtless be explained on the assumption that the "normal allele" (Rt') involved in Okaiku 3 is semi-dominant over rt.
Since the heterozygote, Rt'/rt, is completely fertile, but definitely exhibit a sign of the presence of rt gene, this will be useful for maintenance and genetic study of the gene for rattail character.
Fig. 1 Three types of spikes appeared in the progeny
of an intermediate type (center) plant derived from a cross Okaiku 3 x
a heterozygote Rt/rt.
from left to right: normal, intermediate & rattail.
