EVIDENCE FROM POLYGENE MAPPING FOR A CAUSAL RELATIONSHIP BETWEEN POTATO-TUBER DORMANCY AND ABSCISIC-ACID CONTENT

In previous studies polygene mapping of a backcross population derived from haploid potato (Solanum tuberosum) and a diploid wild species (S olanum berthaultii) showed at least eight quantitative trait loci (QTL s) associated with tuber dormancy. The same population was mapped for abscisic acid (ABA) content in tubers so that any QTLs identified coul d be compared with those detected previously. At least three distinct loci on three chromosomes (2, 4, and 7) were associated with variation in ABA content. One of the QTLs was detected only as a main (single l ocus) effect, and two QTLs were found through two-locus interaction an alysis (epistasis). Interaction between QTLs at markers TG234 (chromos ome 2) and TG155 (chromosome 4) explained 20% of total phenotypic vari ance for this trait. The interaction closely resembled one previously detected for dormancy, suggesting an association between high ABA cont ent and long tuber dormancy. Although relationships between ABA level and dormancy could be demonstrated through polygene mapping, there was no indication of a relationship between these traits when they were s ubjected to a conventional correlation test. This illustrates the usef ulness of polygene mapping as a tool to identify possible associations between hormone levels and plant development.