Figure 5.

Rate of Tuberization of Full-Length St BEL5 Transgenic Lines.

Previous work on the analysis of transgenic lines that overexpressed St BEL5 was done with the coding sequence only (A) (Chen et al., 2003). In this experiment, transgenic lines overexpressing the full-length St BEL5 transcript (A), including ∼650 nucleotides of the UTRs (accession number AF406697) were tested. Line 7540 is nontransformed S. tuberosum ssp andigena. Evaluations were performed on 10 plants per line cultured on Murashige and Skoog (MS) medium with 6% sucrose (B). Plants were scored for time to tuber formation under LDs (earliness), number of tubers after 14 LDs, and total tuber yield after 56 d under SD conditions in vitro. The greenhouse LD experiment was with soil-grown plants. The top five lines (asterisks) tuberized as soil-grown plants in 10-cm pots after 8 weeks under LD conditions in the greenhouse. Most of these tubers ranged from 1.5 to 2.5 cm in diameter (C). Overexpression lines of the coding sequence only (Chen et al., 2003) did not form tubers under LDs even after 6 months in the greenhouse. The means of the St BEL5-FL lines for earliness, tuber number, and yield were significantly greater than the 7540 control plants at P = 0.05 (Fisher's test), and this difference is designated by the letters a or b. ND, not detected.