PNL Volume 14
1982
RESEARCH REPORTS
THE BEHAVIOR OF GENE efr FOR EARLINESS IN NEW RECOMBINANTS UNDER SHORT-
DAY PHYTOTRON CONDITIONS
Gottschalk, W. Institute of Genetics, University of Bonn
Federal Republic of Germany
The reaction of gene efr under controlled short-day conditions in
some recombinant types was discussed previously (1). In the meantime,
new recombinants, homozygous for efr but different for other mutant
genes, have been selected and developed into pure lines. Thirty-eight
of them were grown together with their mother variety and recombinant
R 46C (the donor of gene efr) in our phytotron under short-day condi-
tions as follows: 11 hrs full light (30,000 lux); 12 hrs darkness; 1 hr
dim light (1/2 hour before and 1/2 hr after full light); humidity, 60%;
temperature, 25 C in light, 15 C in dark. Eight normally developed
plants per genotype were grown in Mischerlich pots and the number of
days to flowering was recorded. Some other traits, such as position of
the first flower at the stem, plant height, number and length of inter-
nodes, seed production, and fresh and dry weight, were also determined.
Their flowering behavior is graphically presented in Fig. 1. In spite
of the homozygosity of the material studied and the equal environmental
conditions, there was considerable variation in number of days to
flower.
The mean value for R 46C was 39.3 days, individual values ranging
between 35 and 48 days. The corresponding mean of the mother variety
'Dippes Gelbe Viktoria' was 53-1 days with a range of 47 to 62 days.
Thus, the plants of R 46C started flowering about 14 days earlier than
fch'3 control plants under the conditions of this experiment.
Many recombinant types, homozygous for efr and specific other
genes, showed about the same flowering behavior as R 46C so the other
mutant genes involved apparently had little or no influence on the ac-
tion of gene efr. A few recombinants flowered earlier:
Host recombinants tested, however, flowered considerably later than
those of R 46C. Details can be seen in Fig. 1. Some of the genotypes
began flowering about the same time as the non-early mother variety or
even later. They are early due to homozygosity for gene ,efr. but this
gene is not able to manifest its normal action, presumably because of
its interaction with other mutant genes. Moreoever, Fig. 1 shows
another well-known feature: the later the plants flower, the greater
the variation in days to flower. The mean value for R 570, for example,
was 54.9 days, i.e. about 15 days later than R 46C. Of the 8 plants
studied, however, two flowered simultaneously with R 46C whereas the
others were much later. The causes for this behavior are not yet known,
but they are obviously connected with the tendency to form tiny floral
buds at low nodes which do not develop into normal flowers.
The most interesting recombinant of the group is R 713. derived
from the cross of the fasciated mutant 107D x R 46C. The plants are
homozygous for the following genes: efr for earliness (from R 46C);
