THE GENOTYPIC CONSTITUTION OF SOME LINEARLY FASCIATED RECOMBINANTS DERIVED FROM THE STRONGLY FASCIATED MUTANT 489C

12 RESEARCH REPORTS

PNL Volume 13

1981

Gottschalk, W.

Institute of Genetics, University of Bonn, Federal Republic of Germany

Mutant 489C of the variety 'Dippes Gelbe Viktoria' (DGV) shows a pro-

nounced stem fasciation in the upper part of the stem combined with a strong

shortening of the uppermost internodes. It is homozygous for about 15 mutant

genes, most of them being hypostatic. Therefore, their action cannot be

discerned in the mutant itself but only in specific recombinant types selected

after having crossed 489C with non-fasciated genotypes. The mutant contains

at least three, possibly four, genes causing different kinds of stem fascia-

tion, the gene for strong fasciation being epistatic over the other genes

of this group. Moreover, five different mutant genes for plant height and

internode length are present in 489C1/. In 1980, they caused the following

lengths of the main stem:

The gene for long internodes was found to be epistatic over the other four

genes of this system. Some fasciated recombinant types were crossed with

non-fasciated genotypes in order to clarify their genotypic constitution

particularly with regard to the presence or absence of hypostatic genes.

Theoretically, a variety of recombinants should be expected from such hybridi-

zations differing from each other with regard to the total number of mutant

genes derived from the parental mutant 489C. Hypostatic genes for a slightly

reduced chlorophyll content and for extremely late flowering and ripening

are not considered in these investigations. The following results were ob-

tained :

Recombinant R 98B - from the cross of mutants 489C x 176 (narrow leaves, gene

dim-1) . The plants show the following characters: Short I (from 489C); lineal

stem fasciation, uppermost internodes not shortened (from 489C); stem in the

top region often bifurcated (from 489C); later than the mother variety (from

489C); small seeds (either gene sg from 489C or the pleiotropic gene dim-1

from 176A). In F2 of the cross DGV x R 98B, only two classes of phenotypes

were observed: Normal plants, equal to the mother variety, R 98B. Thus,

recombinant R 98B has a very simple genotypic constitution. Not present in

its genome are: The epistatic genes for strong fasciation and for long inter-

nodes of 489C, and the hypostatic genes very long, short II, short III of

489C.

Recombinant R 161 - from 489C x 1201A (dichotomous stem bifurcation, gene

bif-1). Characters: Short I (from 489C); linear stem fasciation (from 489C);

later than DGV (From 489C); stem bifurcation (probably from 1201A). According

to the F2 segregations of the cross R 161 x DGV, the following genes of 489C

are not present in the genome of R161: The epistatic genes for strong fasciation

^1/— Definite symbols are not yet given to the genes of mutant 489C because it is

not yet clear whether some of them are identical with Pisum genes already

designated.

PNL Volume 13 1981

RESEARCH REPORTS

and for long internodes; the hypostatic genes very long, short II, short III;

and gene sg for reduced seed size.

Recombinant R 661 - from 489C x 26 (extremely shortened internodes; plant

height only about 15 cm). Characters: Plant height equal to 489C; very weak

linear fasciation (from 489C); normal seed size (from 26); normal flowering

time (from 26). According to the F₂ of the cross R 661 x DGV, the following

genes of 489C are not present in the genome of R 661: The epistatic gene

for strong fasciation; the hypostatic genes very long, short I, short II;

the gene for lateness.

Recombinant R 667 - from 489C x 169 (chlorina). Characters: Plant height

equal to 489C; very weak linear fasciation (from 489C); reduced seed size

(gene sg_ of 489C); normal flowering time (from 169). According to the F2

of the cross R 667 x DGV, the following genes of 489C are not present in the

genome of R 667: The epistatic gene for strong fasciation; the gene for

lateness; whereas the hypostatic genes very long, short I, short II, and

probably also short III as well as the gene for stem bifurcation are present.

Thus, R 667 has a much more complicated genotypic constitution than the other

recombinants mentioned so far.

Recombinant R 177 - from 489C x 1201A (dichotomous stem bifurcation; gene

bif-1). Characters: Reduced grain size (gene sg of 489C); stem in the upper

part of the shoot bifurcated (gene bif-1 of 1201A); possibly a gene for weak

stem fasciation (from 489C). According to the F₂ of the cross R 177 x DGV,

the recombinant contains exclusively gene sg and perhaps one of the fasciata

genes of 489C whereas all the other genes of the mutant are not present.

R 177 is the simplest recombinant type selected in all the crosses in which

mutant 489C has been used as one of the partners.