Dynamics of the evolution of the genus of agrostis revealed by GISH/FISH
Genomic changes in related species undergoing human-driven and natural selection are important and biologically interesting. The genus Agrostis is an ideal model for studying the evolution of plants since it has not undergone artificial selection for the past thousands of years. Fluorescence in situ hybridization (FISH) or genomic in situ hybridization (GISH) technology is an effective method for analyzing genome homology and organization, detecting genomic rearrangements, and karyotyping based on visual features. In this study, GISH was performed on two tetraploid species, A. capillaris (2n = 4x = 28, A1A1 A2A2) and A. stolonifera (2n = 4x = 28, A2A2 A3A3), using genomic DNA from a putative ancestral diploid species A. canina (2n = 2x = 14, A1A1) as a probe. Genomic in situ hybridization results revealed that the two tetraploid species underwent intergenomic translocations and genomic rearrangements and demonstrated that the A1 genome is highly homologous to the A2 genome. We discovered the phenomenon of concentric parental genome separation in the nucleus of A. stolonifera in which the two parental genomes (A2 and A3) were spatially separated with limited intermixing and were of concentric arrangements. The FISH results showed that the distribution of 45S rDNA loci varied among the three species. The results of our study suggest that substantial genomic alterations occurred during the evolution of the genus of Agrostis.