PNL Volume 16 1984

RESEARCH REPORTS

INFLUENCE OF TEMPERATURE ON THE FLOWERING BEHAVIOR OF EARLY FLOWERING

GENOTYPES

Gottschalk, W. Institute of Genetics, University of Bonn

Federal Republic of Germany

Eight pea genotypes, homozygous for genes efr for earliness, bif-1

for dichotomous stem bifurcation and for some other mutant genes, were

grown together with the late flowering mother variety 'Dippes Gelbe

Viktoria ' (DGV) under three different temperatures in the phytotron as

follows:

- 12.5°C constant

- 12.5°C night, 25.5°C day

- 25.5°C constant

Other environmental factors were identical in the three trials.

The plants were grown under long-day conditions with 18 hr light and

6 hr darkness; humidity was about 60%. The dots given in Fig. 1 repre-

sent the mean values of the trait "number of days from sowing to

beginning of flowering", based on 8 normally developed plants of each

genotype. Genes efr and bif-1 derive from recombinant R 46C. R 46C was

crossed with other genotypes of our collection and the following recom-

binants were used for the experiments:

- R 20D: efr, bif-1 with full penetrance, "long III", reduced

chlorophyll content

- R 20E: efr, bif-1 with full penetrance, "short II"

- R 427: efr, bif-1 with low penetrance, dim for reduced size of

all plant organs, "short I"

- R 831: possibly identical with R 427

- R 836: efr, bif-1 with extremely low penetrance, "wax 445" for

waxlessness, "short I"

- R 837: efr, bif-1 with reduced penetrance, "wax 423" for

waxlessness, "short I"

- R 879: efr, bif-1 with reduced penetrance, "short I"

As expected, most of the genotypes tested flowered earlier under

high temperature than low. This is exemplified by the first 6 recora-

binants shown in Fig. 1. At 12°C they flowered a month later than at

25°C. In DGV the delay was somewhat more. The difference in time to

flower between the plants grown under constant 25°C and those grown

under 12°C night/25°C day was small, demonstrating that the low night

temperature had a minimal effect on flowering time.

Plants of recombinants R 20D and R 20E showed a specific behavior

in that they formed tiny flower buds at very low nodes as does R 46C,

the donor of gene efr. Fully developed flowers, however, were produced

considerably later on higher nodes. In R 20D, grown under constant

25°C, they appeared more than 7 weeks after sowing, and in R 20C more

than 10 weeks after sowing. In both cases, only some of the plants

flowered at all, whereas the others did not produce fully developed

flowers until the trial was stopped. Therefore, the values for these

two genotypes, given in Fig. 1, are not true mean values. Under con-

stant low temperature of 12°C, plants of R 20D required more than 13

weeks to reach flowering, and those of R 20E more than 16 weeks. Some

plants of R 20E did not flower at all. Under alternating high and low



	12 PNL Volume 16 1984	RESEARCH REPORTS

	temperatures (i e. under approximately normal conditions), however these two recombinants flowered earlier than at constant 25°C.