Comparison of salt tolerance during seed germination and vegetative growth in tomato by QTL mapping

The purpose of this study was to determine the genetic relationship between salt tolerance during seed germination and vegetative growth in tomato by comparing quantitative trait loci (QTLs) which confer salt tolerance at these two developmental stages. A salt-sensitive Lycopersicon esculentum line (NC84173; maternal and recurrent parent) was hybridized with a salt-tolerant accession (LA722) of Lycopersicon pimpinellifolium, and BC1 and BC1S1 populations were developed. The BC1 population was used for RFLP mapping and the BC1S1 population for evaluation of salt tolerance during germination and vegetative growth. The results indicated the presence of a small but significant correlation (r = -0.22, p < 0.05) between rate of seed germination and the percentage of plant survival under salt stress. Seven and five QTLs were identified for salt tolerance during seed germination and vegetative growth, respectively. While in most cases the location of QTLs for germination was different from that for vegetative growth, there were some coincidences in QTL locations; this was consistent with the small phenotypic correlation observed between the two traits. The overall results indicated that, in these tomato genetic materials, salt tolerance during seed germination was independent of that during vegetative growth. However, simultaneous improvement of tolerance at the two developmental stages should be possible through marker-assisted selection and breeding.