Chromosome studies in barley (Hordeum vulgare L.)

Abstract

The effects of the major pre-treatments on the characteristics of the morphology of barley (Hordeum vulgare L.) were compared and evaluated. Colchicine and ice water were found to be particularly effective for basic karyological analysis, such as a chromosome count. 1-bromonaphthalene, 8-hydroxyquinoline and paradichlorobenzene produced satisfactory chromosomes suitable for all levels of karyological analysis, including differential staining. Paradichlorobenzene, which had not previously been used on barley, was found to be a suitable pre-treatment for barley chromosomes. Reducing the temperature at which chromosomes were pre-treated had the effect of reducing the variation within treatments.

The use of DMSO (dimethyl sulfoxide) was evaluated and it was generally found to be of no advantage in the pre-treatment of barley chromosomes. However, DMSO did improve features of the morphology of colchicine treated chromosomes.

Chromosome identification was attempted from measurements and observations of conventionally stained chromosomes. Although chromosomes 5. 6 and 7 could be readily identified, the remaining chromosomes could not be. Errors in karyotype construction were found to be due to 'arm reversal’, 'reversal of order' and differential chromosome contraction.

Differential staining was attempted with limited success. Chromosomes banding in barley was found to be both difficult to obtain and inconsistent. Suggested improvements in the techniques may yield successful results. Chromosome breakage was observed to be random and suggestions were made for improvements in the technique used. These would allow for the study of more localized bands and may contribute to the study of the nature of heterochromatin.