Pseudogamic production of dihaploids and monoploids in Solanum tuberosum and some related species

Attempts were made to maximize frequencies of dihaploids from Solanum tuberosum, obtained through pseudogamy after pollination with S.phureja. Factors influencing dihaploid frequencies were studied: genetics of the pollinator effect, genetics of the seed parent effect and interaction between the two effects on dihaploid frequencies. Temperature influences were determined in a growth chamber experiment. The mechanism of dihaploid formation was studied with the aid of cytological techniques. The pollinator effect was confirmed. Five or more loci were involved and the within-locus interaction was intermediate. High numbers of hybrids had a negative but small effect on numbers of dihaploids. The seed parent effect was also confirmed. The frequency of dihaploids was determined by the sporophyte rather than by the gametophyte of the seed parent. No interaction was found between the pollinator and seed parent effect on the dihaploid frequency. Low temperature had a positive effect on the dihaploid frequency via the pollinator, but no effect was found via the seed parent. Not the 2n-pollen but the n-pollen proved to be instrumental in dihaploid induction. Monoploids were produced from diploid S. tuberosum and S. verrucosum using several S. phureja genotypes as pollinator. The n-pollen induced the haploids in this case as well. Doubled monoploids were obtained with good female fertility.