THE SEED PRODUCTION OF EARLY FLOWERING FASCIATED PISDM RECOMBINANTS
Gottschalk, W. Institute of Genetics, University of Bonn
Federal Republic of Germany
Our high-yielding fasciated mutants have some negative characters
which reduce their breeding value. They are too late and too tall;
moreover, they are homozygous for gene .sg. for reduced seed size.
Theoretically, the breeding value of these genotypes could be improved
by eliminating some of these negative traits. This sems to be possible
since the characters just mentioned are not part of pleiotropic patterns
of the fasciata genes. Instead, they are controlled by independently
acting genes. Another approach to improvement is to incorporate useful
genes from other mutants.
An important consideration bearing on this objective is the fact
that the fasciated mutants are homozygous for 14-18 mutant genes. Thus,
highly heterozygous hybrids arise when they are crossed with non-
fasciated genotypes. Complicated segregations occur in their progenies
and a great number of different recombinant types can be selected. They
have been propagated and are available in the form of pure lines at our
institute.
Most of the genes present in our fasciated mutants are hypostatic
and are therefore not discernible in the plants. This holds true also
for some genes controlling traits of agronomic interest such as inter-
node length, plant height, flowering, and ripening.
We have crossed these mutants with recombinant R 46C carrying gene
efr for early flowering. A large number of fasciated recombinants with
different genotypic constitution is available, all of them containing
efr. as additional mutant gene. These early flowering, fasciated recom-
binants have been tested for seed productivity. They are compared to
both parental groups (the fasciated mutants and the early flowering
recombinant R 46C) as well as to the mother variety used for our ir-
radiations in Fig. 1.
As the figure shows, R 46C did not yield as well as the mother
variety, pooled mean for all the 23 generations tested being only 13% of
the control value. Thus, the genotype cannot be utilized agronomical ly
in its present form. The fasciated mutants, on the other hand, were
found to have an excellent seed production in most generations tested
(lefthand part of the figure). In the righthand part, the yield of 44
different recombinant strains is given, homozygous for efr. for one or
several genes of the polymeric fasci ata group, and for different genes
controlling internode length. They are subdivided into four groups ac-
cording to their plant height.
The first sub-group contains recombinants with the genes "short
III" and "short II" having plant heights ranging between 20 and 50
centimeters. In spite of the stem fasciation, their yield was very low,
about similar to that of the non-fasciated R 46C. Thus, stem fasciation
does not lead to an increase of the seed production in the presence of
the genes for strongly reduced internode length. The recombinants of
the second sub-group contain gene "short I" in addition to efr and fas-
ci ata genes which reduce the internode length only slightly. Their seed
production was better than that of the first group but considerably
