BGN 10: Translocations and inversions in barley induced by fast neutrons and N-nitroso-N-methylurea (MNUA) BARLEY GENETICS NEWSLETTER, VOL. 10, II. RESEARCH NOTES
Szarejko and Maluszynski, pp. 67-69

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 only 6.32%.

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.
 

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