Crossover shortage in potato is caused by StMSH4 mutant alleles and leads to either highly uniform unreduced pollen or sterility

Corentin Clot, Dennis Klein, Joey Koopman, Cees Schuit, Christel Engelen, Ronald Hutten, Matthijs Brouwer, Richard Visser, Martina Juranić, Herman van Eck*

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review

Abstract

The balanced segregation of homologous chromosomes during meiosis is essential for fertility and is mediated by crossovers. A strong reduction of crossover (CO) number leads to the unpairing of homologous chromosomes after the withdrawal of the synaptonemal complex. This results in the random segregation of univalents during meiosis I and ultimately to the production of unbalanced and sterile gametes. However, if CO shortage is combined with another meiotic alteration that restitutes the first meiotic division, then uniform and balanced unreduced male gametes, essentially composed of non-recombinant homologs, are produced. This mitosis-like division is of interest to breeders because it transmits most of the parental heterozygosity to the gametes. In potato, CO shortage, a recessive trait previously referred to as desynapsis, was tentatively mapped to chromosome 8. In this article, we have fine-mapped the position of the CO shortage locus and identified StMSH4, an essential component of the class I crossover pathway, as the most likely candidate gene. A seven base-pair insertion in the second exon of StMSH4 was found to be associated with CO shortage in our mapping population. We also identified a second allele with a 3820 base-pair insertion and confirmed that both alleles cannot complement each other. Such non-functional alleles appear to be common in potato cultivars. More than half of the varieties we tested are carriers of mutational load at the StMSH4 locus. With this new information, breeders can choose to remove alleles associated with CO shortage from their germplasm to improve fertility or to use them to produce highly uniform unreduced male gametes in alternative breeding schemes.
Original languageEnglish
Article numberiyad194
JournalGenetics
Volume226
Issue number1
Early online date7 Nov 2023
DOIs
Publication statusPublished - 3 Jan 2024

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