20 RESEARCH REPORTS PNL Volume 12 1980
A DWARFY' PISUM GENOTYPE WITH AN EXCEPTIONALLY HIGH PHYSIOLOGICAL EFFICIENCY
Gottschalk, W. Institute of Genetics, University of Bonn, West Germany
The spontaneously arisen acacia mutant of Blixt's collection is homo-
zygous for gene tlw causing terminal leaflets instead of tendrils. It was
crossed with our X-ray induced fasciated mutant 489C homozygous for, among
other mutant genes, at least 4 genes responsible for different internode
lengths. In F2, a dwarfy non-fasciated recombinant with acacia leaves was
selected. It was crossed with recombinant R 46C homozygous for genes efr
(earliness) and bif-1 (stem bifurcation) giving rise to recombinant R 455.
The plants of this remarkable recombinant are only about 25 cm long
whereas the plant height of the mother variety 'Dippes gelbe Viktoria',
used for our treatments, is about 85 cm, that of R 46C about 70 cm. In
spite of their dwarfness and strongly reduced leaf area, the number of seeds
per plant was equal to Dippes gelbe Viktoria and surpassed that of R 46C
by more than 10% in 1979. This was due both to a high number of pods per
plant and a relatively high number of seeds per pod (although the seed size
is reduced). The plants of R 46C, used as one of the cross-parents for
producing R 455, flower 7-10 days earlier than the mother variety because
the lowest inflorescences are already formed at the 4th to 6th node
(Dippes gelbe Viktoria: 10th to 14th node). However, the plants do not
produce any seeds in the first 3-5 inflorescences although the meiotic
behavior and the pollen fertility are completely normal. This behavioró
together with certain structural anomalies of the lowest flowers which,
however, do not influence their fertility - appears regularly in each
generation and evidently is part of the pleiotropic action of the efr
gene. lor this reason, plants of R 46C did not exhibit an improved seed
yield. This disadvantage does not occur in the dwarfy plants of recombinant
R 455. They begin to flower even earlier than R 46C and ripen considerably
earlier and all flowers produce seeds. This behavior in comparison with
R 46C could be due to an alteration of the pleiotropic action of gene efr
under the influence of the gene for strong reduction of the internode length.
The surprisingly good seed production of the dwarfy plants of R 455,
equal to that of vigorous pea plants of normal stature, indicates a very
high physiological efficiency of the dwarfs. This will be analyzed in more
detail. However, the absence of tendrils reduces the standability of
this line leading to considerable seed damage in wet summers. We shall
therefore replace the tlw gene of R 455 by the af gene of the afila mutant.
Dwarfy recombinants homozygous for the genes efr, af and the gene for
strongly reduced plant height would have an excellent standing ability and
would thus be better suited than R 455 for cultivation in the field.