FASCIATION AND HETEROSIS IN PEA (III)

38 PNL Volume 14 1982 RESEARCH REPORTS

Loenning, W. E. Institute of Genetics, University of Bonn

Federal Republic of Germany

Another six thousand plants have been devoted to the problem of

fasciation and heterosis, leading to definitive results.

I. Six fasciated lines, each with a different stem length, were crossed

to a common line, 'Dippes Gelbe Viktoria' (non-fasciated):

a) 489 C x mother variety Dippes Gelbe Viktoria (DGV)

b) 251 A x DGV

c) R 710 x DGV

d) R 875 x DGV

e) Mutant 1/74 (of Vasileva's collection) x DGV

f) Mutant VI/10 (of Vasileva's collection) x DGV

Dominance for superior length was evidenced by 3:1 segregations in

F3 and backcrosses of long, nonfasciated recombinants, derived from the

heterotic hybrids, with Dippes Gelbe Viktoria (including segregations).

Since the degree of hybrid vigor varied with the fasciated lines used,

it can be concluded that the dominant genes for length were contributed

by the fasciated parents. The following facts show that the fasciata

genes themselves are responsible for the suppression of the dominant

genes in the fasciated lines:

a) Originally long lines are shortened by fasciation. The

original length can be regained by recombination. Example: F1

mutant 1/74 x R 46 C was as long as mutant's 1/74 mother

variety 'Ramonski', the length of which could be regained by

recombination.

b) The recessive fasciata genes cause growth anomalies, shortening

several internodes but never elongating them in comparison with

the long recombinants.

c) Heterozygotes segregating for only one fasciata gene are as

long as the related nonfasciated homozygous lines but the fas-

ciated lines are shorter.

d) Full length has only been regained in nonfasciated

recombinants.

No heterotic stimulus of heterozygous fasciata genes could be found

by the different methods applied (1).

II. Seed production, a polygenic trait, showed many interactions with

genes for other characters, leading to a more complicated situation.

There is no doubt, however, that seed production can also be affected

strongly by fasciation. Three different cases can be cited at present,

where the high seed production of the hybrids has been fixed in

recombinants: R 710 x DGV, Mut 1/74 x DGV, and, in part, 478 C x DGV.

For the latter, the results were contradictory during the last two

years. In 1980 a recombinant was as productive as the hybrid; in 1981

the latter surpassed the former. Crossing highly reproductive recom-

binants (derived from the heterotic hybrids) with DGV has led to hybrids

which compare favorably with the better parent.

All things considered, the investigation of some 15,500 plants

(including more than 40 different hybrid stocks with replication of a



	38 PNL Volume 14 1982 RESEARCH REPORTS

	FASCIATION AND HETEROSIS IN PEA (III) Loenning, W. E. Institute of Genetics, University of Bonn Federal Republic of Germany Another six thousand plants have been devoted to the problem of fasciation and heterosis, leading to definitive results. I. Six fasciated lines, each with a different stem length, were crossed to a common line, 'Dippes Gelbe Viktoria' (non-fasciated): a) 489 C x mother variety Dippes Gelbe Viktoria (DGV) b) 251 A x DGV c) R 710 x DGV d) R 875 x DGV e) Mutant 1/74 (of Vasileva's collection) x DGV f) Mutant VI/10 (of Vasileva's collection) x DGV Dominance for superior length was evidenced by 3:1 segregations in F3 and backcrosses of long, nonfasciated recombinants, derived from the heterotic hybrids, with Dippes Gelbe Viktoria (including segregations). Since the degree of hybrid vigor varied with the fasciated lines used, it can be concluded that the dominant genes for length were contributed by the fasciated parents. The following facts show that the fasciata genes themselves are responsible for the suppression of the dominant genes in the fasciated lines: a) Originally long lines are shortened by fasciation. The original length can be regained by recombination. Example: F1 mutant 1/74 x R 46 C was as long as mutant's 1/74 mother variety 'Ramonski', the length of which could be regained by recombination. b) The recessive fasciata genes cause growth anomalies, shortening several internodes but never elongating them in comparison with the long recombinants. c) Heterozygotes segregating for only one fasciata gene are as long as the related nonfasciated homozygous lines but the fas- ciated lines are shorter. d) Full length has only been regained in nonfasciated recombinants. No heterotic stimulus of heterozygous fasciata genes could be found by the different methods applied (1). II. Seed production, a polygenic trait, showed many interactions with genes for other characters, leading to a more complicated situation. There is no doubt, however, that seed production can also be affected strongly by fasciation. Three different cases can be cited at present, where the high seed production of the hybrids has been fixed in recombinants: R 710 x DGV, Mut 1/74 x DGV, and, in part, 478 C x DGV. For the latter, the results were contradictory during the last two years. In 1980 a recombinant was as productive as the hybrid; in 1981 the latter surpassed the former. Crossing highly reproductive recom- binants (derived from the heterotic hybrids) with DGV has led to hybrids which compare favorably with the better parent. All things considered, the investigation of some 15,500 plants (including more than 40 different hybrid stocks with replication of a



PNL Volume 14	1982	RESEARCH REPORTS 39

few outstanding cases and segregation and selection from F2 - F5, with backcrosses and their segregations) during the last three and a half years has clearly pointed to recessive epistasis and dominance as the main causes of the heterosis observed in crosses of fasciated with non- fasciated lines. 1. Loenning, W. E. 1982. Theor. Appl. Genet, (in press).