GENETIC-VARIATION AT STORAGE PROTEIN-CODING LOCI OF COMMON WHEAT (CV CHINESE-SPRING) INDUCED BY NITROSOETHYLUREA AND BY THE CULTIVATION OF IMMATURE EMBRYOS IN-VITRO

Electrophoretic patterns of seed storage proteins, the high-molecular- weight glutenins and gliadins, were studied in 468 plants of the commo n wheat cultivar 'Chinese Spring' regenerated from callus culture of i mmature embryos, in 115 plants grown from seeds treated with nitrosoet hylurea and in 260 control plants. From 5 to 21 single grains were ana lysed from each plant. In these three groups, the frequency of inherit ed mutations causing the loss of all proteins controlled by a locus (n ull-mutations, probably caused by a chromosomal deficiency) was 0.69%, 2.07%, and 0.05% per locus (the differences were statistically signif icant), respectively, while that of mutations causing: the loss of a s ingle protein band was 0.11%, 0.33%, and 0.05%, respectively. The loss of all of the gliadins controlled by Gli-B1 or Gli-B2 (mutations were probably caused by a deletion of satellites of the corresponding chro mosomes), was significantly higher than the loss of gliadins controlle d by genomes A and D. Gene mutations altering the electrophoretic mobi lity of a single protein band in the pattern were found only in the se cond group of plants (0.44%). Therefore, chemical mutagenesis which pr oduced not only more mutations than cultivation of immature wheat embr yos in vitro, but also a higher ratio of mutations that altered DNA se quences, can be considered as an easier and comparatively more promisi ng way for obtaining new improved variants of loci controlling biochem ical characteristics in wheat. Somaclonal variation, on the other hand , was probably mainly caused by chromosomal abnormalities and could th erefore hardly be considered as a useful tool in wheat breeding.