Cytogenetic and molecular characteristics of rye genome in octoploid triticale (× Triticosecale Wittmack)

Abstract

Alloploidization resulting from remote (interspecific or intergeneric) hybridization is one of the main factors in plant evolution, leading to the formation of new species. Triticale (× Triticosecale Wittmack, 1889) is the first artificial species created by crossing wheat (Triticum spp.) and rye (Secale cereale Linnaeus, 1753) and has a great potential as a grain and forage crop. Remote hybridization is a stress factor that causes a rapid reorganization of the parental genomes in hybrid progeny (“genomic shock”) and is accompanied by abnormalities in the chromosome set of hybrids. The formation of the hybrid genome and its subsequent stabilization are directly related to the normalization of meiosis and the correct chromosome segregation. The aim of this work was to cytogenetically characterize triticale (× Triticosecale rimpaui Wittmack, 1899, AABBDDRR) obtained by crossing Triticum aestivum Linnaeus, 1753. Triple Dirk D × Secale cereale L. Korotkostebel’naya 69 in F3–F6 generations of hybrids, and to trace the process of genetic stabilization of hybrid genomes. Also, a comparative analysis of the nucleotide sequences of the centromeric histone CENH3 genes was performed in wheat-rye allopolyploids of various ploidy as well as their parental forms. In the hybrid genomes of octoploid triticale an increased expression of the rye CENH3 variants was detected. The octoploid triticale plants contain complete chromosome sets of the parental subgenomes maintaining the chromosome balance and meiotic stability. For three generations the percentage of aneuploids in the progeny of such plants has been gradually decreasing, and they maintain a complete set of the paternal rye chromosomes. However, the emergence of hexaploid and new aneuploid plants in F5 and F6 generations indicates that stabilization of the hybrid genome is not complete yet. This conclusion was confirmed by the analysis of morphological features in hybrid plants: the progeny of one plant having the whole chromosome sets of parental subgenomes showed significant morphological variations in awn length and spike density. Thus, we expect that the results of our karyotyping of octoploid triticales obtained by crossing hexaploid wheat to diploid rye supplemented by comparative analysis of CENH3 sequences will be applicable to targeted breeding of stable octo- and hexaploid hybrids.

Karyotype Reorganization in Wheat–Rye Hybrids Obtained via Unreduced Gametes: Is There a Limit to the Chromosome Number in Triticale?

“…As such, in stable hybrids, the CENH3 produced by one parent must be able to support the functionality of the other parent's centromeres, despite differences in each parent's centromere sequences [83]. Thus, the conservation of chromosome sets of the parental subgenomes in octoploid triticale over generations may be associated with the increased expression of rye centromeric histone CENH3 variants in the new genomic environment [108] Unexpectedly, we detected the preservation of rye 4R chromosomes in a monosomic or disomic state up until generation F 5 . While in F 2 , the chromosome pair 4R4R only supplemented the wheat chromosome set [69], in F 5 , 4R4R was added to wheat chromosomes in 58.59% of plants and replaced chromosomes of the fourth homeologous group in 13.15% of plants, which implies its compensational and competitive activity in a new genomic environment.…”

Karyotype Analysis, Genomic and Fluorescence In Situ Hybridization (GISH and FISH) Reveal the Ploidy and Parental Origin of Chromosomes in Paeonia Itoh Hybrids

“…[ 7 , 8 ], hexaploid wheat ( Triticum aestivum L.) and chrysanthemum ( Chrysanthemum morifolium Ramat.) [ 9 , 10 ], and octoploid strawberry ( Fragaria × ananassa ) and triticale (× Triticosecale Wittmack) [ 11 , 12 ]. The odd polyploid varieties are also domesticated for special breeding purposes, such as triploid seedless watermelon [ 13 ].…”

Phylogenetic and Expression Analysis of CENH3 and APOLLO Genes in Sexual and Apomictic Boechera Species

“…Mutations at the N-terminal tail of CENH3 disturb chromosome segregation in meiosis and often lead to sterility [20,24]. Null mutations in CENH3 also cause chromosome elimination and were proposed as a tool to produce haploid plants [25][26][27][28].…”