FURTHER GENES INFLUENCING THE PENETRANCE OF GSNE bif-1 FOR STEM BIFURCATION

PNL Volume 15

1963

RESEARCH REPORTS

FURTHER GENES INFLUENCING THE PENETRANCE OF GSNE bif-1 FOR STEM

BIFURCATION

Gottschalk, W. and A. Abou-Salha Institute of Genetics

University of Bonn, Federal Republic of Germany

The penetrance of gene bi f-1 for dichotomous stem bifurcation,

hornoz ygous] y present in mutant 1201A of our collection, depends on both

errvironmentai factors and other mutant genes of the genome (1). During

the past years, further genes were found to influence its penetrance

positively or negatively; some of them are discussed in the present

paper. The method used consists in comparing bifurcated recombinants

with mutant 1201A with regard to the penetrance of bif-1 .

Mutant 1201A, the donor of bif-1 . shows a broad variation of

penetrance ranging between 22 and 84% in 20 generations due to a

specific environmental factor(s) which is not yet known to us.

The 10 different recombinants studied can be subdivided into three

groups according to the penetrance behavior of bif-1 (Fig. 1, upper

part). The 4 genotypes of Group I show in principle the same degree of

penetrance as mutant 1201A. This means that those mutant genes, which

additionally present in their genomes, do not influence the

penetrance of bif-1 .

A different picture emerges in Group II. Recombinant RM 83 6 was

selected after having crossed the waxless mutant 445 with R 46C,

homozygous for bif-1 and gene efr for earliness. In two generations,

the action of bif-1 was not expressed (P=0%). In the other three gener-

ations tested the penetrance was extremely low, ranging between 2 and

4%. Thus, the gene for waxlessness suppresses the penetrance of bif-1

almost completely. A similar behavior was observed in recombinant

RM 427 arisen in F2 of the cross of mutant 176A with recombinant R 862,

which itself arose after having hybridized the fasciated mutant 123 with

the early flowering recombinant R 46C. The plants of RM 4 27 have the

folowing characters:

Stem bifurcation (gene bif-1 from R 46C)

Early flowering (gene efr from R 46C)

Narrow leaflets and stipules (gene dim-1 from mutant 17 6A)

Slightly reduced internode length (gene short I from mutant 123)

In this combination, the penetrance of bif-1 ranged between 0 and

15%. Thus, one of the other mutant genes present in RM 427 likewise has

a suppressing effect on the penetrance of bif-1 .

The opposite effect was observed in 4 recombinants of Group III.

In R 177, RM 516, and RM 1010, the penetrance of bif-1 varied between 86

and 100% over 3 to 10 generations. All the plants of RR 507 were bifur-

cated, i.e. full penetrance of the gene. The 4 recombinants have the

following genotypic constitutions:

R 177: Stem bifurcation (bif-1 from 1201A)

Reduced seed size (sg. from the fasciated mutant 489C)

R 507: Stem bifurcation (bif-1 from 1201A)

Reduced seed size (sg from 489C)

Reduced internode length (short-I from 489C)

RM 516: Stem bifurcation (bif-1 from 1201A)

Reduced internode length (short I from the fasciated

mutant 251 A)

Later flowering (from 251 A)

HM 1010: Stem bifurcation (bif-1 from 1201A)

Later flowering (from 489C)

PNL Volume 15

1983

RESEARCH REPORTS

These 4 recombinants do not have a specific gene in common which could

be responsible for stabilizing the penetrance of bif-1. In R 177 and

RR 507, this effect could be due to the presence of gene sg for small

grains. This gene, however, is not present in the genomes of RM 516 and

RM 1010. Both these genotypes begin flowering a few days later than the

mother variety, but this is not a very reliable trait.

The seed production of the material tested i- given in the lower

part of Fig. 1. A strong correlation between see< yield and penetrance

of bif-1 could not be found, as is evident if wo compare the recom-

binants of Group I with mutant 1201A. The penetrance of bif-1 is about

equal to, but the seed production of the 4 recombinants is considerably

lower than, that of mutant 1201A. If, however, we compare the genotypes

of Groups II and III with each other, a certain parallelism between

penetrance behavior and seed production is evident. At least in some of

these genotypes, the low or high penetrance could contribute to the low

or the high yield, respectively.

1. Gottschalk, W. 1978. PNL 10:13.

Upper part: The penetrance of gene bif-1 in mutant 1201A

(the donor of the gene) and in 10 recombinant lines

homozygous for bif-1 and for other mutant genes.

Lower part: The seed production (number of seeds per plant)

of the 11 genotypes studied as related to the correspond-

ing values of the mother variety 'Dippes Gelbe Viktoria'

(DGV; = 100%.

Each dot give the mean value for one generation.