Erratum: Aegilops crassa Boiss. repeatome characterized using low-coverage NGS as a source of new FISH markers: application in phylogenetic studies of the Triticeae.

[This corrects the article DOI: 10.3389/fpls.2022.980764.].

Aegilops crassa Boiss. repeatome characterized using low-coverage NGS as a source of new FISH markers: Application in phylogenetic studies of the Triticeae.

Aegilops crassa Boiss. is polyploid grass species that grows in the eastern part of the Fertile Crescent, Afghanistan, and Middle Asia. It consists of tetraploid (4x) and hexaploid (6x) cytotypes (2n = 4x = 28, D1D (Abdolmalaki et al., 2019) XcrXcr and 2n = 6x = 42, D1D (Abdolmalaki et al., 2019) XcrXcrD2D (Adams and Wendel, 2005), respectively) that are similar morphologically. Although many Aegilops species were used in wheat breeding, the genetic potential of Ae. crassa has not yet been exploited due to its uncertain origin and significant genome modifications. Tetraploid Ae. crassa is thought to be the oldest polyploid Aegilops species, the subgenomes of which still retain some features of its ancient diploid progenitors. The D1 and D2 subgenomes of Ae. crassa were contributed by Aegilops tauschii (2n = 2x = 14, DD), while the Xcr subgenome donor is still unknown. Owing to its ancient origin, Ae. crassa can serve as model for studying genome evolution. Despite this, Ae. crassa is poorly studied genetically and no genome sequences were available for this species. We performed low-coverage genome sequencing of 4x and 6x cytotypes of Ae. crassa, and four Ae. tauschii accessions belonging to different subspecies; diploid wheatgrass Thinopyrum bessarabicum (Jb genome), which is phylogenetically close to D (sub)genome species, was taken as an outgroup. Subsequent data analysis using the pipeline RepeatExplorer2 allowed us to characterize the repeatomes of these species and identify several satellite sequences. Some of these sequences are novel, while others are found to be homologous to already known satellite sequences of Triticeae species. The copy number of satellite repeats in genomes of different species and their subgenome (D1 or Xcr) affinity in Ae. crassa were assessed by means of comparative bioinformatic analysis combined with quantitative PCR (qPCR). Fluorescence in situ hybridization (FISH) was performed to map newly identified satellite repeats on chromosomes of common wheat, Triticum aestivum, 4x and 6x Ae. crassa, Ae. tauschii, and Th. bessarabicum. The new FISH markers can be used in phylogenetic analyses of the Triticeae for chromosome identification and the assessment of their subgenome affinities and for evaluation of genome/chromosome constitution of wide hybrids or polyploid species.

The Association of Grain Yield and Agronomical Traits with Genes of Plant Height, Photoperiod Sensitivity and Plastid Glutamine Synthetase in Winter Bread Wheat (Triticum aestivum L.) Collection.

The reduction in plant height caused by mutations in Rht-B1 or Rht-D1 (Reduced height-1) genes in combination with day-length-independent early flowering associated with the Ppd-D1 (Photoperiod-D1) gene were the main factors of the drastic yield increase in bread wheat in the 1960s. Increasing nitrogen use efficiency as well as maintaining high yields under conditions of global climate change are the modern goals of wheat breeding. The glutamine synthetase (GS) enzyme plays a key role in ammonium assimilation in plants. In previous studies, the TaGS2-A1 gene, coding the plastid isoform of GS, was shown to be connected with nitrogen use efficiency in wheat. Using the polymerase chain reaction (PCR) markers, the association of yield and agronomical traits with haplotypes of Rht-B1, Rht-D1, Ppd-D1 and TaGS2-A1 genes was studied in a diverse collection of winter bread wheat cultivars grown in Krasnodar (Russia). In the three-year experiment, semidwarfism and photoperiod insensitivity were confirmed to be highly favorable for the grain yield. The TaGS2-A1b haplotype had a tendency for increased grain yield and lodging resistance, but mainly in plants not possessing the 'green revolution' alleles. Thus, TaGS2-A1b may have potential in breeding wheat cultivars with alternative dwarfing genes or tall cultivars, which may be optimal for growing under certain environments.

qPCR as a Selective Tool for Cytogenetics.

qPCR is widely used in quantitative studies of plant genomes and transcriptomes. In this article, this method is considered as an auxiliary step in the preparation and selection of markers for FISH analysis. Several cases from the authors' research on populations of the same species were reviewed, and a comparison of the closely related species, as well as the adaptation of the markers, based on satellite tandem repeats (TRs) using quantitative qPCR data was conducted. In the selected cases, TRs with contrast abundance were identified in the cases of the Dasypyrum, Thinopyrum and Aegilops species, and the transfer of TRs between the wheat and related species was demonstrated. TRs with intraspecific copy number variation were revealed in Thinopyrum ponticum and wheat-wheatgrass partial amphidiploids, and the TR showing predominant hybridization to the sea buckthorn Y chromosome was identified. Additionally, problems such as the absence of a reference gene for qPCR, and low-efficiency and self-complementary primers, were illustrated. In the cases considered here, the qPCR results clearly show high correlation with the subsequent results of the FISH analysis, which confirms the value of this method for cytogenetic studies.