A quantitative method of karyotypic analysis applied to the soybean, Glycine max.

Abstract

Karyotypic analysis is difficult in the soybean which has numerous small chromosomes, not readily recognizable morphologically. Investigation is complicated by the technical problems of spreading and staining the chromosomes. A quantitative approach to karyotypic analysis is described using data from six cells selected on the basis of degree of contraction of the chromosomes and which were shown to be homogeneous statistically. Scatter diagrams were prepared from data on total length and arm ratios of the chromosomes to determine the homologous pairs of chromosomes. These data from the haploid complement values of the six cells were then plotted to identify as far as possible the individual chromosomes. Nine of the 20 chromosomes of the haploid complement were identified and described individually and the remaining 11 were characterized into classes based on length and arm ratio. A standard karyotype of the soybean is proposed. The method should be useful for karyotypic analysis of other species with problems similar to those of the soybean. The procedure should also prove useful for further work in the soybean itself, such as identification of chromosomes involved in monosomic, trisomic or other aneuploid conditions. This work is the first to provide a standard karyotype of the soybean.