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).Meiotic 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.
Highlights
Polyploidization is a significant evolutionary mechanism in all organisms
Plants with the gametic chromosome number were used for cytological studies of first division restitution (FDR)-like restitution mechanisms
Unreduced gamete formation by interspecific hybrids is a mechanism which potentially plays a crucial role in evolution, but about which very little is known (Mason and Pires 2015)
Summary
Polyploidization (increase in the number of genomes present) is a significant evolutionary mechanism in all organisms. In comparison to natural meiosis, as a result of which four haploid cells (reduced gametes, “n”) are obtained, unreduced gametes are formed when meiosis results in only two cells with the somatic chromosome number (“2n”). This type of meiosis was named restitution, as it returns the same number of chromosomes in the gamete as are present in the parent organism (Ramanna and Jacobsen 2003). Omission of either the first or second meiotic division is commonly observed (Silkova et al 2011)
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