Random amplified polymorphic DNA markers detected in a segregating hybrid population of Solanum chacoense*S. phureja

Development of SCAR markers to the PVY resistance gene Ryadg based on a common feature of plant disease resistance genes

Sequence-characterized amplified regions (SCARs) were developed, based on nucleotide differences within resistance gene-like fragments isolated from a potato plant carrying the Ryadg gene, which confers extreme resistance to potato Y potyvirus (PVY). It originates from Solanum tuberosum subsp. andigena, and a susceptible potato plant. SCARs were tested using 103 potato breeding lines and cultivars with diverse genetic backgrounds derived from Europe, North America, and Japan. Two markers showed high accuracy for detection of the Ryadg gene. The SCAR marker RYSC3 was generated only in genotypes carrying Ryadg. The SCAR marker RYSC4 was detected in all genotypes carrying Ryadg but also in four PVY-susceptible genotypes. Neither marker was detected in genotypes carrying other Ry genes originating from different species than S. tuberosum subsp. andigena. Therefore, these SCAR markers should be powerful tools in marker-assisted selection for Ryadg in potato breeding programs, and should also be useful for cloning of the Ryadg gene. Key words: SCAR, potato virus Y, extreme resistance gene, Solanum.

Analysis of the genetic composition of anther-derived potato by randomly amplified polymorphic DNA and simple sequence repeats

Randomly amplified polymorphic DNA (RAPD) and simple sequence repeat (SSR) analyses were used to characterize the genetic composition of anther-derived plants of a diploid potato clone, CP2 (Solanum chacoense 80-1 x S. phureja 1-3). The ploidy of anther-derived plants was first determined by flow cytometry. A total of 44 decamer primers was screened for RAPD polymorphism. The loci that segregated were selected and scored. The monoploids had less than half as many loci carrying RAPD markers compared with the anther donor. Among 14 anther-derived diploids, 5 were identified as homozygous by marker frequency similar to monoploids and 9 as heterozygous. Five of seven SSRs obtained from published potato sequences were polymorphic in CP2. CP2 was found to be heterozygous with two alleles at four SSR loci (TC/TA, AAG, AGA, CTT) and three alleles at a ACTC locus. Primer pairs flanking each of the five polymorphic SSRs revealed that monoploids had only the allele contributed by S. chacoense 80-1. Homozygous diploids had only one band per SSR locus, whereas heterozygous diploids displayed more than one allele for at least one SSR locus. Results of the SSR analysis supported the findings based on RAPD markers; the same five diploid clones were characterized as homozygous by both SSR and RAPD markers.