Corentin R. Clot, Lea Vexler, Maria de La O Leyva-Perez, Peter M. Bourke, Christel J. M. Engelen, Ronald C. B. Hutten, José van de Belt, Erik Wijnker, Dan Milbourne, Richard G. F. Visser, Martina Juranić & Herman J. van Eck

Theoretical and Applied Genetics; April 2024; vol. 137; article 79

Key message

Multiple QTLs control unreduced pollen production in potato. Two major-effect QTLs co-locate with mutant alleles of genes with homology to AtJAS, a known regulator of meiotic spindle orientation.

Abstract

In diploid potato the production of unreduced gametes with a diploid (2n) rather than a haploid (n) number of chromosomes has been widely reported. Besides their evolutionary important role in sexual polyploidisation, unreduced gametes also have a practical value for potato breeding as a bridge between diploid and tetraploid germplasm. Although early articles argued for a monogenic recessive inheritance, the genetic basis of unreduced pollen production in potato has remained elusive. Here, three diploid full-sib populations were genotyped with an amplicon sequencing approach and phenotyped for unreduced pollen production across two growing seasons. We identified two minor-effect and three major-effect QTLs regulating this trait. The two QTLs with the largest effect displayed a recessive inheritance and an additive interaction. Both QTLs co-localised with genes encoding for putative AtJAS homologs, a key regulator of meiosis II spindle orientation in Arabidopsis thaliana. The function of these candidate genes is consistent with the cytological phenotype of mis-oriented metaphase II plates observed in the parental clones. The alleles associated with elevated levels of unreduced pollen showed deleterious mutation events: an exonic transposon insert causing a premature stop, and an amino acid change within a highly conserved domain. Taken together, our findings shed light on the natural variation underlying unreduced pollen production in potato and will facilitate interploidy breeding by enabling marker-assisted selection for this trait.

See https://link.springer.com/article/10.1007/s00122-024-04563-7

Fig.1: Distinctive metaphase II orientation phenotypes in parental clones. a–c DAPI-stained chromosome spreads of male meiocytes at metaphase II. a Normal and b parallel orientation of metaphase II plates, c fused metaphase II plates. (d) Proportion of meiocytes with normally oriented (left), parallel (middle), or fused metaphase II plates (right) for the parental clones of population FRW19-112 in pink and IVP16-560 in blue. Median values per orientation and per clone are indicated by vertical bars. Significantly different median values between clones for a given orientation are indicated by different letters. Scale bars = 10 µm