5 RESEARCH REPORTS PNL Volume 11 1979
AEFFECT OF GENOTYPIC BACKGROUND AND ENVIRONMENT ON THE EXPRESSION OF THE dgl MUTANT
Gottschalk, W. Institute of Genetics, University of Bonn, West Germany

 

Plants of the X-ray induced mutant 142B of our collection, homozygous
for gene dgl, are small in stature (about 35 cm). Their small leaves develop
brown spots and degenerate completely during ontogenetic development. Only
the uppermost leaves are normal green and capable of photosynthesis. Seed
production is very low, ranging between 10 and 35% of the control values
of the initial variety over 9 generations of comparison at Bonn.
The mutant was crossed with some other mutants, and recombinants homo-
zygous for dgl and the respective other genes were selected and propagated.
A gene for stem fasciation, derived from mutant 489C, did not influence the
action of dgl with regard to leaf degeneration. The seed production, however,
was more than doubled due to an increase in the number of flowers which accom-
panies stem fasciation (recombinant R 142D).
Plant height of recombinant R 142C was the same as that of the initial
variety. The leaves were severely damaged due to the presence of dg1 . A
further increase in seed production over 142B was realized by combining a
gene for very low degree of stem fasciation, likewise derived from 489C.
PNL Volume 11
1979
RESEARCH REPORTS
Gene dgl was also combined with genes for long internodes and lateness.
In this combination, the effect of dgl was strongly reduced. The degenera-
tion was limited to the lower leaves, the middle and upper leaves remaining
normal (recombinant R 142F}. This led to a further increase in seed pro-
duction up to about 700% of 142B.
These results show that the 5 mutant genes tested (2 different genes
for stem fasciation, 2 genes for increased internode length, 1 gene for
lateness) all influenced the selection value of dgl positively. One of them
reduced the specific effect on leaf degeneration.
When mutant 142B is grown in a greenhouse, gene dgl does not express
its action; all the leaves are normal green. The mutant also failed to
manifest when grown in Egypt. The plants were vigorous and reached the height
of the mother variety with full seed production. Thus, an environmental
factor (s)—probably high temperature—suppresses the action of dgl. Seeds
of these plants were sown in the field in Bonn and strongly damaged plants
developed from them.
The influence of other genes and of environmental conditions on the
action of gene dgl is schematically given in Fig. 1.
Fig. 1. The improvement of mutant 142B by changing the environmental
conditions and the genotypic background.