In Vitro Osmotic Stress Tolerance in Potato and Identification of Major QTLs

Identification of quantitative trait loci (QTL) responsible for stress tolerance could help to develop new tolerant potato cultivars through markers-assisted selection. The objective of the research was to identify and map loci that may play major role in the control of osmotic stress tolerance in potato under in vitro vegetative growth conditions. Mannitol-induced osmotic stress response of cv. White Lady and breeding line S440 as well as their 85F(1) progeny for root number and root length under in vitro conditions was investigated. Interval mapping based on 200 informative markers produced a molecular marker map comprising 13 linkage groups for White Lady and 14 for S440. In total, 14 QTLs with LOD > 2 were identified from which 6 were confirmed as major QTLs. Of those six, three were associated with root length and three with root number. For root length, one major QTL was identified on chromosome XII (LOD = 4.8), which explained 52.3 % of the phenotypic variance. Two other major QTLs from an unidentified chromosome explained 64.9 and 51 % of the phenotypic variance with LODs of 5.34 and 4.8, respectively. For root number, one QTL with 19.2 % of the phenotypic variance (LOD of 2.9) was tentatively identified on chromosome IX, while another was putatively identified on chromosome XII (LOD of 2.4), together explaining 26.8 % of the phenotypic variance.