32 PNL Volume 18 1986 RESEARCH REPORTS
Kasperek, G.
Department of Genetics and Plant Breeding!
Academy of Agriculture, Poznan, Poland|
The plant materials used for po1yploidization were genetic lines
derived from hybrids obtained through crossing of local populations of
Polish and Russian pea. After treating seeds and plants in different
stages of development with various C-mitotic agents (both physical and
chemical) it became evident that the only effective combinations involved
treating germinating seeds with water solutions of colchicine 0.005% x 12h
and 0.05% x 2 4h (1).
The obtained autotetraploids of pea (4x=28) were characterized by
changes in whole plant anatomy, morphology, and development in comparison
with the diploidal initial line (2x=14). For example:
(1) Polyploids showed gigantism, manifesting as enlarged leaves,
stomates, flowers, and pollen grains, thick stems, increased 1OOO-seed
weight, and seed protein content. These plants also had more intensive
pigmentation of green parts and flowers as well as a tendency toward
prolonged vegetative and reproductive development (especially evident in
years of great rainfall).
(2) Polyploid plants in comparison with diploid plants had fewer
stomates, a tendency toward bushy growth, fewer pods on branches, and fewer
two-podded nodes, as well as fewer seeds per plant and seeds per pod.
Polyploids, in spite of their luxuriant growth during the vegetative
period, were clearly inferior to the diploid initial form during the
reproductive phase.
A considerable reduction of fertility of autotetrap1oid plants
prompted us to search for the cause oi this phenomenon. There were no sig-
nificant differences between 2x and 4x plants in the number of ovules per
pod (2x=6.6-7.4; 4x=6.5-7.3). Examination of mitosis revealed certain
disorders (chromosomes beyond the equatorial plate in metaphase, chromosome
bridges and lagging chromosomes in anaphase), hut these disorders were
relatively rare (2.07% cells with disorders out of 5800 dividing cells
examined). A greater number of irregular configurations was observed
during the meiotic division, analyzed during microsporogenosis.
Polyvalents, multivalent chromosome associations, chromosome bridges,
metaphase II with an unequal number of chromosomes in the equatorial
plates, chromosomes remaining outside the daughter nuclei, tetrads with
micronuclel, and polyades appeared in 11.4% of the ceils in a total of 4696
analyzed. Thus, the number of irregularities observed during meiosis was
comparatively small. Pollen viability was also rather high and pollen
grain stainability, using the Belling agent, revealed only a slight reduc-
tion in vitality of the tetraploid lines (87.9%-94.6%) as compared with the
initial diploid line (98.4%). Therefore we may have to look to
megas por ogenes i s or to abnormalities in the zygotic phase or the emhryo-
forming stage for the reasons for low fertility in the autotetrap1oids.
The low percentage of irregularities observed in mitosis and meiosis
was the reason for the high stability of the mutant karyotype. In several
succeeding pedigreed generations no plants were found with an unbalanced
chromosome set; aLl plants examined were euploids of 4x=28 chromosomes.
Kasperak, G. 1974. Roczniki AR w Poznanin LXXIII:57-63.