Similarity of QTLs detected for in vitro and greenhouse development of potato plants

A relationship between quantitative trait loci (QTLs) detected for in vitro and greenhouse growing conditions was studied in a backcross population of 155 genotypes derived from a haploid potato (Solanum tuberosum) and a dipl oid wild species (S. berthaultii). Both plant height and tuberization earli ness were characterized under two growing conditions. Main-effect QTLs and QTLs identified only through interaction were detected for each of the trai ts. For traits associated with plant height as well as for traits associate d with early tuberization, the most significant QTL detected for greenhouse cultivated plants was also found when the population was grown in vitro. T he most significant QTL for earliness of tuberization in vitro, which was l ocated on chromosome 8, coincides with that detected for sucrose concentrat ion in leaf exudate. The absence of a S. berthaultii allele was associated both with a higher amount of sucrose in the exudate and with earlier in vit ro tuber formation. Epistasis was found to have a significant effect on all traits investigated. The QTL model that included main-effect QTLs and all significant interactions explained 83-88% of the total genetic variance for each of the developmental traits. The possibility of using an in vitro sys tem combined with marker-assisted selection for preliminary selection of ea rly tuberizing clones is discussed.