28 RESEARCH REPORTS

PNL Volume 13

1981

WELLENS1EK'S CQCHLEATA x DIPPES GELBE VICTORIA - ANOTHER CASE OF RECESSIVE

EPISTASIS AND DOMINANCE

Loennig, W. E. Institute of Genetics, Bonn, Federal Republic of Germany

The neutron-induced cochleata mutant of Wellensiek affects stipule mor-

phology, causing a conversion to spoon-shaped structures. The plants also

are thinner and a bit shorter than their IL. Furthermore the marked flower

anomaly associated with this mutant sharply decreases the number of seeds per

plant. In the F1 of coch x 'Dippes Gelbe Viktoria¹, the negative influence

of the recessive cochleata gene is eliminated by the normal allele of Dippes

Gelbe Viktoria and the dominant alleles for extraordinary plant height and

seed production present in the genome of the cochleata mutant in a hypostatic

state result in heterosis in F1 (Fig. 1). The cross was repeated in 1979 and

corroborated the earlier results.

Further evidence: (1) the IL

of this cochleata mutant, Wellen-

siek' s 'Dominant' (unknown to the

author when he began studying

the first hybrids described above)

as well as the F1 Dominant x DGV

compare in length and seed produc-

tion with the hybrid cochleata

x DGV. (2) Some non-segregating

F3 families of cochleata x DGV

show length and seed production

comparable with Dominant. (3) In

relation to DGV, flowering and

ripening was delayed in the hybrids.

The difference between heterosis

in this case and that induced

by the fasciated mutants seems

to be simple: One IL, Wellensiek's

Dominant, already possesses the

dominant genes whose action is

partly suppressed by the coch

gene of the mutant. In the fas-

ciated mutants the respective

genes have mutated to the dominant

state. But in both cases the

full expression of the dominant

genes is hindered by deleterious

recessives and no heterozygosity

per se seems to be involved.

Fig. 1. Mean length, seeds per plant,

thousand seed weight, and mean

total dry weight of plants of

DGV, Wellensiek's coch, and

their F1.