II. 33. Types of chromosomal aberrations induced by artificial seed aging in barley.
M. Murata, T. Tsuchiya, Department of Agronomy, Colorado State University, Fort Collins, Colorado 80523; and E.E. Roos, National Seed Storage Laboratory, USDA-SEA-AR, Fort Collins, Colorado 80523.
In our studies on artificially aged barley seeds (see preceding paper), various types of chromosomal aberrations were observed. Chromosomal aberrations at the first anaphases in roots from artificially aged (at 38 C 18% moisture content, 32 C - 18%, 38 C - 12%, and 32 C - 12%) seeds were classified into nine categories (Table 1). Single bridges (Fig. 1b, c), single fragments (Fig. 1e) and double bridges (Fig. 1d) comprised 80% of the aberrations. Frequencies of other types were low.
Table 1. Types of chromosomal aberrations induced by artificial seed aging and their frequencies.
Among bridges, the "sticky-end type" of aberration, which is thought to be induced by sister chromatid exchanges, was observed most frequently. Some fragments seemed to be produced by breaks on either or both sides of the point of the sticky bridge. A combination of double bridge and double fragment (Fig. 1f), thought to result from chromosome-type breaks, accounted for only two out of 578 aberrations (0.3%). Abdalla and Roberts (1968) and others indicated that most aberrations resulting from seed aging were caused by chromosome-type breaks. However, the present result suggests that the chromosomal aberrations induced by artificial seed aging are due to the chromosomes sticking at anaphase. Furthermore, it is suggested that the chromatid-type aberrations occurred more frequently than the chromosome-type in artificially aged seeds.
Reference:
Abdalla, F.H. and E.H. Roberts. 1968. Effects of temperature, moisture, and oxygen on the induction of chromosome damage in seeds of barley, broad beans, and peas during storage. Ann. Bot. N. S. 32:119-136.
