Repetitive DNA, Genome and Species Relationships in Avena and Arrhenatherum(Poaceae)

Repetitive sequences have been widely used for examining genomeand species relationships by in situ and Southern hybridization.In the present study, double-stranded DNA sequences, from denaturedDNA reannealed to Cot = 1, from Avena strigosa(2 n = 2x = 14;A genome; referred to as CotA) and Avena sativa(2n = 6 x =42; ACD genome; referred to as CotACD) were isolated with ahydroxyapatite column, and were used for in situ hybridizationon hexaploid A. sativa chromosomes. Probe CotACD labelled allchromosomes evenly throughout their length at the same intensity.Probe CotA labelled the 28 A and D genome chromosomes stronglyand the 14 C genome chromosomes weakly. Three cloned repetitivesequences, pAvKB9 (126 bp), pAvKB26 (223 bp) and pAvKB32 (721bp) were characterized in the A, B, C and D Avena genomes andthe genus Arrhenatherum using molecular and cytological methods.Clones pAvKB9 and pAvKB26 were absent from the Avena C genome,while both could identify the presence of the D genome by Southernhybridization. In situ hybridization to diploid and tetraploidAvena species revealed that the probes showed a dispersed genomicorganization and that they are present on both arms of all chromosomes.These sequences were excluded from areas where tandem repeats,such as rRNA genes and telomeres, are present. These resultsindicate the close relationship between A and D genomes andthe presence of common DNA sequences between A and C Avena genomes.All three clones hybridized to Southern blots containingArrhenatherumdigested genomic DNA, indicating Arrhenatherum’s closeaffinity to A, B and D Avena genomes. Copyright 2000 Annalsof Botany Company Cereals, DNA, hydroxyapatite, in situ hybridization, oats, reassociation kinetics, repetitive DNA