EFFECT OF GENOTYPIC BACKGROUND AND ENVIRONMENT ON THE EXPRESSION OF THE dgl MUTANT

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.