Genomic relationships among diploid and hexaploid species of Andropogons established through GISH

Abstract

Andropogon is a pantropical grass genus comprising 100–120 species and found mainly in the grasslands of Africa and the Americas. While the genomic relationships between many Andropogon species have been resolved by studying chromosome behavior in interspecific hybrids, relationships between the North and South American diploids have remained elusive. Further, the genome composition of two hexaploid species (including the important forage grass Andropogon lateralis Nees) has been unclear because of the strong hybridization barriers that exist between species. Consequently, genomic in situ hybridization was applied to shed light on these issues. The results confirmed that (i) both the South American (Andropogon selloanus (Hack.) Hack., Andropogon macrothrix Trin.) and North American (Andropogon gyrans Michx.) diploid species shared a common S genome and (ii) the S genome comprises just one of the three genomes in the hexaploids A. lateralis Nees and Andropogon bicornis L. The evolutionary and taxonomic implications of these findings are discussed.Key words: Andropogon, polyploidy evolution, Poaceae, genomic in situ hybridization, taxonomy.