Comparison of salt tolerance during seed germination and vegetative growthin 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 the se two developmental stages. A salt-sensitive Lycopersicon esculentum line (NC84173; maternal and recurrent parent) was hybridized with a salt-toleran t accession (LA722) of Lycopersicon pimpinellifolium, and BC1 and BC1S1 pop ulations were developed. The BC1 population was used for RFLP mapping and t he BC1S1 population for evaluation of salt tolerance during germination and vegetative growth. The results indicated the presence of a small but signi ficant correlation (r = -0.22, p < 0.05) between rate of seed germination a nd the percentage of plant survival under salt stress. Seven and five QTLs were identified for salt tolerance during seed germination and vegetative g rowth, respectively. While in most cases the location of QTLs for germinati on was different from that for vegetative growth, there were some coinciden ces in QTL locations; this was consistent with the small phenotypic correla tion observed between the two traits. The overall results indicated that, i n these tomato genetic materials, salt tolerance during seed germination wa s independent of that during vegetative growth. However, simultaneous impro vement of tolerance at the two developmental stages should be possible thro ugh marker-assisted selection and breeding.