The production of aneudihaploids in Solanum tuberosum L. group Tuberosum (the common potato)

Summary

Trisomic cytotypes were produced in dihaploid (diploid) plants of Solanum tuberosum L. Group Tuberosum, the common potato, according to two methods. Firstly, the aberrant types were selected, through chromosome counting, from parthenogenic dihaploid offspring of tetraploid-diploid crosses. In dihaploid populations from twelve tetraploid potato varieties the frequencies of aneuploids ranged from 3.5 to 11.0%. About 95% of these aneuploids had only one, and the others not more than two extra chromosomes. Secondly, the aneuploids were produced from triploid-diploid crosses. Seedset strongly depended on the crossability of the parental plant material, and the best results were obtained when the motherplants were grafted onto tomato. On avarage the three most successful cross combinations resulted in approximately 0.7 berries per pollination and 6 seeds per berry. With regard to seedsize the seed could be divided in two groups, viz, normal and small seeds. Half of the seed did not germinate or produced inviable seedlings, especially among the small seed group. About 93% of the plants was neuploid, with 25, 26 and 27 being the predominant chromosome number. It was concluded that the production of trisomics was the most successful through triploid-diploid crosses. The results were discussed with reference to the chromosomal behaviour in the meiosis in triploid plants (Lange & Wagenvoort, 1973a). It thus was possible to relate the low seedset to the distribution of chromosomes in the meiotic anaphases. On the one side this distribution resulted in a limitation of the avalability of gametes with monohaploid and near-monohaploid chromosome numbers, while on the other side the macrospores with higher chromosome numbers seemed to be inviable. Finally a crossing scheme was presented for transmitting the trisomic condition into a genetic background with better homogeneity and more homozygosity.