Location: Corn Insects and Crop Genetics ResearchTitle: A Fluorescence In Situ Hybridization System for Karyotyping Soybean) Author
Submitted to: Genetics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/4/2010
Publication Date: 7/1/2010
Citation: Findley, S.D., Cannon, S.B., Varala, K., Du, J., Ma, J., Hudson, M.E., Birchler, J., Stacey, G. 2010. A Fluorescence In Situ Hybridization System for Karyotyping Soybean. Genetics. 185:727-744. Interpretive Summary: The chromosomes of a plant cell, which contain all the information needed to generate the whole plant, can be seen under a microscope. For many applications in genetic research, important chromosomal features or genetic abnormalities can be seen directly under a microscope if the individual chromosomes can be identified. However, in many organisms, including soybean, the chromosomes are small and difficult to distinguish. This paper describes a protocol that applies fluorescent labels to uniquely identify the 20 chromosomes of soybean. The paper also reports breakages and rearrangements of several chromosomes in comparison with a wild soybean variety. These techniques and findings are important because they provide a method to soybean researchers to directly study soybean chromosomes, and to visually identify chromosomal abnormalities that may prevent fertile crosses between some soybean varieties.
Technical Abstract: The development of a universal soybean (Glycine max [L.] Merr.) cytogenetic map that associates classical genetic linkage groups, molecular linkage groups and a sequence-based physical map with the karyotype has been impeded due to the soybean chromosomes themselves, which are tiny and morphologically homogeneous. To overcome this obstacle, we screened soybean repetitive DNA to develop a cocktail of fluorescent in situ hybridization probes that could differentially label mitotic chromosomes in root tip preparations. We used genetically-anchored BAC clones both to identify individual chromosomes in metaphase spreads and to complete a FISH-based karyotyping cocktail that permitted simultaneous identification of all 20 chromosome pairs. We applied these karyotyping tools to wild soybean, Glycine soja Sieb. and Zucc., which represents a large gene pool of potentially agronomically valuable traits. These studies led to the identification and characterization of a reciprocal chromosome translocation between chromosomes 11 and 13 in two accessions of wild soybean. The data confirm that this translocation is widespread in G. soja accessions and likely accounts for the semi-sterility found in G. soja by G. max crosses.