A maternally inherited DNA marker, descended from Solanum demissum (2n = 6x = 72) to S. tuberosum (2n = 4x = 48)

Abstract

A Mexican hexaploid wild potato species, Solanum demissum (dms), was only used as a female in previous breeding programs. The resulting clones with dms cytoplasm produced abundant, but non-functional pollen. A 170 bp DNA fragment, named Band 1, was originally detected in the F(1) hybrid between dms and S. tuberosum. In this study, the sequenced region was extended to 1,032 bp; nevertheless, it did not show any homology to known sequences. This extended region harboring Band 1 was, without introns, all transcribed to mRNA and was maternally inherited from dms to S. tuberosum through backcrosses. Three dms accessions, 168 accessions of 38 cultivated and closely related wild species, and 158 varieties and breeding lines were surveyed, which demonstrated that Band 1 was specific to dms and varieties and breeding lines with dms cytoplasm. Thus, Band 1 is a useful marker to distinguish dms cytoplasm, which enables us to design efficient mating combinations in breeding programs.

Keywords: DNA marker; Solanum demissum; W/α cytoplasm; backcrossing; cytoplasmic male sterility; transcribed region; unknown sequence.

Fig. 1

A DNA fragment of 1,032 bp harboring Band 1 (underlined in A). Three pairs of primer sequences for amplification of Region 1, 2 and 3 are shown in (A) and the schematic representation in (B).

Fig. 2

Amplification of Region 1 (A), Region 2 (B) and Region 3 (C) from T, D, 5 reciprocal F₁ plants of TD and DT, and 5 BC₁ plants of (TD)T and (DT)T. M denotes λDNA HindIII digests.

Fig. 3

Southern hybridization of MspI (A), HindIII (B) and EcoRI (C) digests of T and D probed with Band 1. Arrows indicate hybridization signals. M denotes λDNA HindIII digests.

Fig. 4

Leaf cDNA and genomic DNA of T, TD, DT and D were amplified for Region 1 (B), Region 2 (C) and Region 3 (D). A β-tubulin gene amplified from leaf cDNA samples exhibited only 525 bp band (A), demonstrating no contamination with genomic DNA. M denotes λ DNA HindIII digests.

Fig. 5

Amplification of Region 2 together with GBSS as a positive control from randomly chosen varieties. Chloroplast DNA types are shown below. 1. Early Rose, 2. Irish Cobbler, 3. May Queen, 4. Desiree, 5. Russet Burbank, 6. Kennebec, 7. Atlantic, 8. Shepody, 9. Snowden, 10. Norking Russet, 11. Tunika, 12. Astarte, 13. Norin 1, 14. Rishiri, 15. Chijiwa, 16. Toyoshiro, 17. Nishiyutaka, 18. Hokkaikogane, 19. Konafubuki, 20. Kita-akari, 21. Touya, 22. Inca-no-mezame. M denotes λDNA HindIII digests.