Wheat Evolution Revealed by the Nuclear and Organellar DNA Analyses1

Abstract

A genomic DNA library was constructed using nuclear DNA of a common wheat Chinese Spring, and the size and copy number per genome of about 320 clones were determined. Using these clones as probes, RFLP analysis of nuclear genomes of nine polyploidy wheats was carried out. From the results obtained, their phylogenetic rela-tionships were considered, and linkage maps of RFLP sites were constructed. Carrier chromosomes were derermined using Sears’ nulli-terasomics of Chinese Spring. RFLP analysis of chloroplast DNAs from all species of the two genera, Triticum and Aegi-lops, led to a classification of their chloroplast genomes into 17 types. A phylogenetic tree of those genomes was drawn based on the number of mutations disclosed between their all possible combinations. RFLP analyses of mitochondrial DNAs were carried out by comparing restriction fragment patterns between closely related species or accessions, and by comparing Southern hybridization patterns between 19 species representing the 16 chloroplast genomes. Mitochondrial genome probed higher evolu-tionary divergence than chloroplast genome. Phylogenetic trees of chloro;last and mitochondrial genomes constructed form the RFLP data had many features in com-mon, and provided critical information in determining maternal lineages of most poly-ploid species. RFLP analyses of nuclear and organellar DNAs demonstrated to be a useful mean s of clarifying different aspects of phylogenetic differentiation.