Genetic instability of a barley shrunken mutant

A putative transposable genetic instability in barley (Hordeum vulgare L.) has produced a shrunken mutation showing xenia, i.e., observable segregation in spikes of the heterozygotes. The enzymology of this mutant in a Bomi-like genetic background has previously been studied (SCHULMAN and AHOKAS 1990). Extracts of its immature shrunken endosperms show 14 % of the activity of soluble starch synthase of a normal Bomi cultivar, which may mean that the gene for soluble starch synthase has been mutated (SCHULMAN and AHOKAS 1990). Six shrunken endosperm, xenia or sex genes have been listed for barley in the review by SDGAARD and VON WETTSTEIN-KNOWLES (1 987). Typical sex/sex plants are viable. A special class of endospermal mutants called des causes defective endosperms, xenia, and lethality (RAMAGE and CRANDALL 1981). The present shrunken mutant displays reduced viability, and the suppressor mutant described below may fall into the dex category. In barley, WISE and ELLINGBOE (1985) understood the occurrence of the resistance gene recombination between M1u6 and Mla13 to be caused by a transposition. SIMONS and SOMERVILLE (1988 and erratum 1990), using the same barley accessions as WISE and ELLINGBOE (1983, obtained results which differed, however. While transposable elements are rare or undocumented for barley (ROHDE et al. 1987; MOORE et al. 1989; FUERSTENBERG and JOHNS 1990), in maize, a cross-pollinating species, they are dynamic factors creating new genetic material in populations where variation is chosen (GRIEL et al.