| The prerequisites for a successful breeding program are sources of genetic variability and an understanding of the inheritance patterns of traits of interest. Wild Solanum species and the cultivated relatives of potato (Solanum tuberosum L.) are valuable sources of desirable genes for potato breeding. The main concern is whether target genes can be transferred along with good tuberization. An understanding of the inheritance of tuberization in potato hybrids is vital to the success of potato breeding programs and can also maximize the use of wild species germplasm. Intensive phenotyping in 16 trials was conducted under eight different photoperiods (20, 18, 16, 14, 12, 11, 10, and 8 hours), three conditions (greenhouse, growth chamber, and the field), and in four years (2007--2010). The phenotypic evaluation showed results that can be applied to potato breeding. The parental background of haploid-wild species hybrids can cause significant variability in the degree of the tuberization response to the photoperiod stimulus. The degree to which stem cuttings are induced to tuberize under a 14-hr photoperiod in a greenhouse is correlated with tuberization of whole plants in the field. To simplify the definition of short and long day conditions in future studies, the designation of a short day condition could be a 12-hr and long day a 14-hr photoperiod. A major QTL was identified on chromosome 5 that accounts for 74% of the variation for tuberization at the 14-hr photoperiod in the greenhouse trial and 39% of the variation for tuber size in summer field trials. A collection of phenotypic data from multiple trials and environments is the key to success in characterizing the genetics of tuberization and developing molecular markers to identify hybrids that can tuberize in field conditions. |
