Diploid strawberry and potato transformed with a transposon tagging construct exhibited either global (strawberry) or local transposition (potato). An activation tagged, compact-sized strawberry mutant overexpressed the gene adjacent to Ds. As major fruit and vegetable crops, respectively, strawberry and potato are among the first horticultural crops with draft genome sequences. To study gene function, we examined transposon-tagged mutant strategies in model populations for both species, Fragaria vesca and Solanum tuberosum Group Phureja, using the same Activation/Dissociation (Ac/Ds) construct. Early somatic transposition during tissue culture occurred at a frequency of 18.5% in strawberry but not in potato transformants. Green fluorescent protein under a monocot promoter was a more reliable selectable marker in strawberry compared to potato. BASTA (gluphosinate herbicide) resistance served as an effective selectable marker for both species (80 and 85% reliable in strawberry and potato, respectively), although the effective concentration differed (0.5% for strawberry and 0.03% for potato). Transposons preferentially reinserted within genes (exons and introns) in both species. Real-time quantitative PCR revealed enhanced gene expression (670 and 298-fold expression compared to wild type in petiole and leaf tissue, respectively) for an activation tagged strawberry mutant with Ds inserted about 0.6 kb upstream from a gene coding for an epidermis-specific secreted glycoprotein EP1. Our data also suggested that endopolyploid (diploid) cells occurring in leaf explants of monoploid potato were the favored targets of T-DNA integration during transformation. Mutants obtained in these studies provide a useful resource for future genetic studies.

Solanum phureja clone 1-3 and S. chacoense clone 80-1 have a zero and high leptine content in their foliage, respectively. An F(1) hybrid (CP2) was intermediate for the trait, but self-incompatible. Two reciprocal backcross families, PBCp ( phu 1-3 x CP2) and PBCc (CP2 x phu 1-3), and a family of monoploids derived by anther culture of CP2, were characterized for leptine as the aglycon, acetylleptinidine (ALD), content in leaves by gas chromatography. ALD was present in 43 of 87 genotypes in the PBCp backcross, implying simple genetic control by a dominant gene. However, the ALD levels were low compared to CP2. In the PBCc backcross, only 7 of 42 genotypes expressed ALD at a level generally higher than in PBCp. This ratio was significantly different from the 1:1 segregation observed in the reciprocal backcross and suggests a cytoplasmic influence. ALD levels in the CP2 monoploids ranged from 0 to 8,968 &mgr;g.g(-1) of dry weight (dw) with 18 individuals expressing ALD and five with 0 ALD content. Ten high (mean ALD = 546 &mgr;g.g(-1) of dw) and ten low (mean ALD = 0) individual plants within PBCp and seven high (mean ALD = 3,037 &mgr;g.g(-1) of dw) and eight low (mean ALD = 0) individual plants within PBCc were used for bulk segregant analysis (BSA) using 214 RAPD (randomly amplified polymorphic DNA) primers. Three RAPD primers (OPQ-2, OPT-16 and OPT-20) amplified bands exclusively in bulks containing DNA mixes of high ALD producers in both PBCp and PBCc populations. These results suggest that these markers were associated in coupling to ALD content. ANOVAs for ALD content verified association between the markers and the trait. A CAPS (cleaved amplified polymorphic sequence) marker, GP82A, was also significantly associated with ALD production in both the monoploid and the PBCp populations. None of the RAPD markers was associated to ALD in the monoploids but one was associated in repulsion. The monoploid data indicate the likelihood of a recessive gene(s) that controls leptine production, but the backcross data indicate the action of modifying loci.