Heritability of meiotic restitution and fertility restoration in haploid triticale

Abstract

Key messageA single division meiosis mechanism of meiotic restitution is incompletely penetrant but significantly associated with restored fertility in triticale haploids (n = 21, genome formula ABR).AbstractMeiotic restitution, or failure of meiosis to produce gametes with a reduced chromosome number, can lead to the restoration of fertility in allohaploids. Meiotic restitution is of major interest for producing doubled haploids, as haploid plants undergoing meiotic restitution can often form seeds without the need to apply mitosis inhibitors to double chromosome number. We aimed to characterize meiotic restitution in a population of 183 haploids (n = 21, genome formula ABR) derived from an F1 wheat-rye hybrid where one parent was known to carry factors responsible for restoration of fertility in wide-cross haploids. Based on cytological analysis, approximately half of the plants analyzed were characterized by normal meiosis, while half showed at least some cytological evidence of meiotic restitution. However, this mechanism was incompletely penetrant in the population, with no individual plant showing 100% unreduced gamete formation: restitution occurred sectorially within each anther and was not observed in all the anthers of a given plant. Hence, the absence of meiotic restitution could not be confirmed conclusively for any individual plant, confounding this analysis. However, cytological observation of meiotic restitution was significantly associated with seed set, further confirming the role of meiotic restitution in fertility restoration. Our results provide insight into this mechanism of unreduced gamete formation, and provide a basis for future work identifying the genetic factors responsible for this trait.

A Review of Unreduced Gametes and Neopolyploids in Alfalfa: How to Fill the Gap between Well-Established Meiotic Mutants and Next-Generation Genomic Resources

“…Diploid meiotic mutants producing viable and unreduced ( n ≥ 2) gametes have been discovered in numerous plants [ 58 ], and although complete penetrance is extremely uncommon, it is thought to be an almost ubiquitous behavior across the entire plant kingdom [ 59 ]. Practically speaking, unreduced gametes are largely employed for polyploidization processes, and to boost the heterosis effect in several crops, including alfalfa [ 51 , 60 ].…”

“…Overall, male and female gamete production is controlled by a complex gene network, but usually n ≥ 2 eggs/pollen are the result of single gene mutations and, consequently, of a loss of protein function that may occur from early meiotic events (prophase I) to cytokinesis II [ 61 ]. In particular, when meiosis I fails to separate homologous chromosomes, we speak generally of “first division restitution” (FDR), while when meiosis II fails to separate sister chromatids, we refer to “second division restitution” (SDR) [ 59 ].…”

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

“…The heritability of meiotic restitution has been described in wheat hybrids [54,67,101]. The genes for meiotic restitution in those studies originated from various accessions of durum wheat T. turgidum [65][66][67][68].…”

“…Functional gametes in wheat-rye F 1 hybrids are formed via meiotic restitution, in which there is no pairing of chromosomes, and univalents are divided into sister chromatids in the first meiosis after which the meiosis ends [64][65][66]. It was found that meiotic restitution is genetically controlled in wheat-rye hybrids [64][65][66][67][68] and inherited in durum wheat-rye hybrids [54,66,67].…”

Understanding In Vitro Tissue Culture-Induced Variation Phenomenon in Microspore System

“…Its action relies on preventing the microtubule formation and chromosome segregation resulting in chromosome doubling [ 180 ]. The process may induce large chromosomal rearrangements [ 185 , 186 ] resulting in somaclonal variation.…”