Identification of QTLs controlling low‐temperature tolerance during the germination stage in cucumber (Cucumis sativus L.)

Poor seed germination of cucumber at suboptimal temperatures is a great concern for growers wishing to take advantage of the early market. The development of low‐temperature‐tolerant varieties would be aided by understanding the inheritance of the trait and mapping its locus. In this study, a set of 140 recombinant inbred lines (RILs) derived from a cross between 65G (low‐temperature‐tolerant) and 02245 (low‐temperature‐sensitive) was used to identify the QTLs linked with low‐temperature tolerance. A linkage map was developed using 135 simple sequence repeat (SSR) markers and five insertion–deletion (Indel) markers, and three QTLs were identified, qLTG1.1, qLTG2.1 and qLTG4.1. qLTG1.1, the major one for germination rate, germination energy and germination index, explained more than 50% of the observed phenotypic variability. The major QTL for radicle length, qLTG4.1, explained 13.8% of the phenotypic variability. The results showed that qLTG1.1 and qLTG4.1 play an important role in low‐temperature tolerance during seed germination of cucumber and provide a basis for further fine mapping to determine the molecular mechanism for this trait.