LAUSR

Haploids have often been used to simplify the genetic complexity of potato due to its high heterozygosity and autotetraploidy. We maintained some haploid plants of wild potato species in vitro that were produced through anther culture almost a half century ago. Among them, a diploid Solanum bulbocastanum and its monohaploid, three monohaploids of S. verrucosum, a disomic tetraploid S. stoloniferum and its dihaploid (all Mexican species) and a dihaploid of the disomic tetraploid S. acaule (South American species) were analyzed morphologically, cytologically and by molecular markers. Their species identity and ploidy levels were confirmed to be correct except for those of a monoploid S. bulbocastanum, which had already experienced natural chromosome doubling. The monohaploids and chromosome-doubled monohaploid were all homozygous in 19,889 SNP loci surveyed. Two of three monohaploids of S. verrucosum were morphologically different but similar by SNP analysis. Most of the heterozygous loci of the tetraploid S. stoloniferum were in a duplex condition. The heterozygous loci of the dihaploid S. stoloniferum were mostly duplexed in the tetraploid S. stoloniferum, suggesting that the alleles are fixed in homoeologous loci. Therefore, each of these haploid-plant genomes is homozygous and is suitable for whole-genome sequencing.