Abstract
Fluorescence in situ hybridization karyotypes have been widely used for evolutionary analysis on chromosome organization and genetic/genomic diversity in the wheat alliance (tribe Triticeae of Poaceae). The karyotpic diversity of Aegilops umbellulata, Ae. markgrafii, Ae. comosa subsp. comosa and subsp. subventricosa, and Ae. uniaristata was evaluated by the fluorescence in situ hybridization (FISH) probes oligo-pSc119.2 and pTa71 in combination with (AAC)5, (ACT)7, and (CTT)12, respectively. Abundant intra- and interspecific genetic variation was discovered in Ae. umbellulata, Ae. markgrafii, and Ae. comosa, but not Ae. uniaristata. Chromosome 7 of Ae. umbellulata had more variants (six variants) than the other six U chromosomes (2–3 variants) as revealed by probes oligo-pSc119.2 and (AAC)5. Intraspecific variation in Ae. markgrafii and Ae. comosa was revealed by oligo-pSc119.2 in combination with (ACT)7 and (CTT)12, respectively. At least five variants were found in every chromosome of Ae. markgrafii and Ae. comosa, and up to 18, 10, and 15 variants were identified for chromosomes 2 of Ae. markgrafii, 4 of Ae. comosa subsp. comosa, and 6 of Ae. comosa subsp. subventricosa. The six Ae. uniaristata accessions showed identical FISH signal patterns. A large number of intra-specific polymorphic FISH signals were observed between the homologous chromosomes of Ae. markgrafii and Ae. comosa, especially chromosomes 1, 2, 4, and 7 of Ae. markgrafii, chromosome 4 of Ae. comosa subsp. comosa, and chromosome 6 of Ae. comosa subsp. subventricosa. Twelve Ae. comosa and 24 Ae. markgrafii accessions showed heteromorphism between homologous chromosomes. Additionally, a translocation between the short arms of chromosomes 1 and 7 of Ae. comosa PI 551038 was identified. The FISH karyotypes can be used to clearly identify the chromosome variations of each chromosome in these Aegilops species and also provide valuable information for understanding the evolutionary relationships and structural genomic variation among Aegilops species.
Highlights
The genus Aegilops serves as a valuable genetic resource for expanding the genetic basis of cultivated bread wheat, as it is closely related to Triticum and has played a pivotal role in the evolution of bread wheat (Schneider et al, 2008)
Six probes were initially screened for one accession each from four diploid species, namely Ae. umbellulata, Ae. markgrafii (PI 542197), Ae. comosa subsp. subventricosa (PI 551068), and Ae. uniaristata (PI 554418) (Figure 1)
It is generally accepted that tandem repeats play a pivotal role in chromosome organization, stabilization, and recombination as well as DNA replication (Heslop-Harrison, 2000; Li et al, 2002; Gemayel et al, 2012)
Summary
The genus Aegilops serves as a valuable genetic resource for expanding the genetic basis of cultivated bread wheat, as it is closely related to Triticum and has played a pivotal role in the evolution of bread wheat (Schneider et al, 2008). Aegilops contains 11 diploid species that harbor different nuclear and cytoplasmic genomes (Van Slageren, 1994). Ae. umbellulata, Ae. markgrafii, Ae. comosa, and Ae. uniaristata are diploid donor species of polyploid Aegilops harboring the U, C, M, and N genomes, respectively. Several methods, including morphological observation (Kawahara, 2002; Tahernezhad et al, 2010), C-banding karyotype (Badaeva et al, 1996a), biochemical markers (Rodríguez-Quijano et al, 2001; Dai et al, 2015), and molecular markers (Sasanuma et al, 2004; Tahernezhad et al, 2010; Thomas and Bebeli, 2010), have been adopted to assess the genetic diversity and evolutionary relationships of Aegilops species. Some cloned repeats and oligonucleotide sequences have been used as probes to establish fluorescence in situ hybridization (FISH) karyotypes rather than C-banding karyotypes due to improved efficiency and easier operation
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