Abstract
Genomic diversity of Portuguese accessions of Avena species—diploid A. strigosa and hexaploids A. sativa and A. sterilis—was evaluated through molecular and cytological analysis of 45S rDNA, and other repetitive sequences previously studied in cereal species—rye subtelomeric sequence (pSc200) and cereal centromeric sequence (CCS1). Additionally, retrotransposons and microsatellites targeting methodologies—IRAP (inter-retrotransposon amplified polymorphism) and REMAP (retrotransposon-microsatellite amplified polymorphism)—were performed. A very high homology was detected for ribosomal internal transcribed sequences (ITS1 and ITS2) between the species analyzed, although nucleolar organizing regions (NOR) fluorescent in situ hybridization (FISH) analysis revealed distinct number of Nor loci between diploid and hexaploid species. Moreover, morphological diversity, evidenced by FISH signals with different sizes, was observed between distinct accessions within each species. pSc200 sequences were for the first time isolated from Avena species but proven to be highly similar in all genotypes analyzed. The use of primers designed for CCS1 unraveled a sequence homologous to the Ty3/gypsy retrotransposon Cereba, that was mapped to centromeric regions of diploid and hexaploid species, being however restricted to the more related A and D haplomes. Retrotransposon-based methodologies disclosed species- and accessions-specific bands essential for the accurate discrimination of all genotypes studied. Centromeric, IRAP and REMAP profiles therefore allowed accurate assessment of inter and intraspecific variability, demonstrating the potential of these molecular markers on future oat breeding programs.
Highlights
Avena genus (2n = 2x = 14) comprises diploid (A and C genomes), tetraploid (AB and AC genomes) and hexaploid (ACD) species
To assess Avena diversity we analyzed distinct repetitive sequences such as 45S rDNA ITS1 and ITS2 and sequences previously mapped on subtelomeric and centromeric (CCS1) domains in other cereal species
Retrotransposons and microsatellites flancking sequences were analyzed through Inter-retrotransposon amplified polymorphism (IRAP) (Inter Retrotransposons Amplified Polymorphism) and retrotransposon-microsatellite amplified polymorphism (REMAP) (Retrotransposons Microsatellite Amplified Polymorphism) methodologies
Summary
Avena genus (2n = 2x = 14) comprises diploid (A and C genomes), tetraploid (AB and AC genomes) and hexaploid (ACD) species. Hexaploid species appear to have arisen by two rounds of hybridization followed by chromosome duplication whereas tetraploid species with AB genomes were suggested to result from an unrelated event involving an A diploid species autopolyploidization (for a review see [1]). Four of 27 Avena species [2] are cultivated and used for food, feed or forage, namely: diploid A. strigosa (A), tetraploid A. abyssinica (AB) and hexaploids. A. strigosa and A. sativa are the major Avena crops in Portugal, which is considered the center of diversity of the former one [1]. Natural hybrids between A. sativa and A. sterilis occur frequently and are widespread in Portugal [3]
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