A Database for Triticeae and Avena
II. 30. Translocations and inversions in barley induced by fast neutrons
and N-nitroso-N-methylurea (MNUA).
I. Szarejko and M. Maluszynski, Department of Genetics, Silesian University,
ul. Jagiellonska 28, 40-032 Katowice, Poland.
The M2 generation resulting from a treatment of three varieties of spring
barley with fast neutrons (900 rads), with MNUA (1.4 mM) and with these
two mutagenic agents applied successively (neutrons 500 rads + MNUA 0.7
mM) partially sterile plants were harvested. Cytological observations of
76 lines in the M3 have segregated into fertile and partially sterile forms,
1:1. Observations were carried out on configuration of chromosomes during
metaphase and anaphase I of meiosis in PMC's.
During metaphase I of 22 M3 lines there occurred configurations which
characterize translocations. Nearly all of the observed translocation rings
contained four chromosomes: obviously the translocations affected a single
mutual exchange between two nonhomologous chromosomes. In only one case
there was found a ring composed of six chromosomes.
In addition to a four-chromosome ring and five bivalents, PMC's of the
translocation heterozygotes of one M3 line were found to contain a single
univalent during metaphase I. Cytological observations of mitosis in meristematic
cells of the root-tip meristem of the offspring of the examined plants
have borne out the assumption of its translocation trisomic character.
In 21 of the lines tested, occurrence of bridges and chromosome fragments
during anaphase I is indicative of inversions. In the majority of plants
with inversions, single bridges were seen; in only two cases double bridges.
Aberrations were most numerous after treatment with fast neutrons and
after joint action of the two mutagenic agents in question. MNUA alone
did not evoke translocations, yet at low frequencies it induced inversions.
There was noticed a differential susceptibility of the studied varieties
to the action of mutagenic agents inducing chromosomal aberrations in that
of the Salka variety, lines with translocations and inversions constitute
10.26% of semi-sterile M2's, whereas in the Menuette variety they constitute
Frequency of occurrence of translocations and inversions as depending
on the mutagenic agent in use and on the variety in question is represented
in tabular form.
Table 1. Frequency of translocations and of inversions
in spring barley as governed bv the mutagenic agent applied.
Table 2. Frequency of translocations and of inversions
in barley as governed by the variety examined.
BGN 10 toc
BGN Main Index