QTL analysis of potato tuberization

Abstract

Quantitative trait loci (QTLs) affecting tuberization were detected in reciprocal backcrosses between Solanum tuberosum and S. berthaultii. Linkage analyses were performed between traits and RFLP alleles segregating from both the hybrid and the recurrent parent using a set of framework markers from the potato map. Eleven distinct loci on seven chromosomes were associated with variation in tuberization. Most of the loci had small effects, but a QTL explaining 27% of the variance was found on chromosome 5. More QTLs were detected while following alleles segregating from the recurrent S. tuberosum parent used to make the backcross than were detected by following alleles segregating from the hybrid parent. More than half of the alleles favoring tuberization were at least partly dominant. Tuberization was favored by an allele from S. berthaultii at 3 of the 5 QTLs detected by segregation from the hybrid parent. The additive effects of the QTLs for tuberization explained up to 53% of the phenotypic variance, and inclusion of epistatic effects increased this figure to 60%. The most common form of epistasis was that in which presence of an allele at each of 2 loci favoring tuberization was no more effective than the presence of a favorable allele at 1 of the 2 loci. The QTLs detected for tuberization traits are discussed in relationship to those previously detected for trichome-mediated insect resistance derived from the unadapted wild species.

Evidence from Polygene Mapping for a Causal Relationship between Potato Tuber Dormancy and Abscisic Acid Content

“…The population analyzed was not large enough to test for interactions involving more than two loci (Tanksley, 1993). The QTLs detected for ABA content were compared with QTLs previously detected for tuber dormancy (Van den Berg et al, 1996b) and for the ability to tuberize under long photoperiods (Van den Berg et al, 1996a). We determined the mean lengths (in days) of tuber dormancy for 2 successive years.…”

“…RFLP mapping of these populations has been carried out (Bonierbale et al, 1994). We have used the mapping information to identify 11 QTLs associated with the ability to tuberize under long days (Van den Berg et al, 1996a) and 9 QTLs for tuber dormancy (Van den Berg et al, 199613). Three of these QTLs coincide, raising the possibility that each of the 3 is the locus of a gene that controls a hormone or other substance affecting …”

“…The population had the mean genome ratio of 75% S. tuberosum, with a range from 50 to 87%. RFLP mapping was carried out on this population by Bonierbale et al (1994), and it is the same population of 155 progenies that was used to find QTLs for tuberization and dormancy (Van den Berg et al, 1996a, 1996b. Because of the heterozygous nature of the parenta1 clones used in these experiments, segregating alleles from both parents contributed to the genetic variation of progenies.…”

“…Statistical analyses of the linkage between RFLPs and ABA level segregating from the hybrid parent were performed by qGene software (Nelson, 1997) and by the MAPMAKER/QTL program (Lincoln and Lander, 1989 Polygene Mapping of ABA Content Related to Potato Dormancy 1455 ered significant for interaction. The population analyzed was not large enough to test for interactions involving more than two loci (Tanksley, 1993).The QTLs detected for ABA content were compared with QTLs previously detected for tuber dormancy (Van den Berg et al, 1996b) and for the ability to tuberize under long photoperiods (Van den Berg et al, 1996a). We determined the mean lengths (in days) of tuber dormancy for 2 successive years.…”

“…We determined the mean lengths (in days) of tuber dormancy for 2 successive years. Tuberization data were from the same population ( Van den Berg et al, 1996a) and consisted of ratings for tuberization on one-node cuttings the 1st and 2nd years and percentage of plants that tuberized early. …”