Key words Lycopersicon esculentum
Restriction fragment length polymorphism (RFLP)
Quantitative trait loci (QTLs)
Springer Online Journal Archives 1860-2000
Abstract Quantitative trait loci (QTLs) contributing to salt tolerance during the vegetative stage in tomato were investigated using an interspecific backcross between a salt-sensitive Lycopersicon esculentum breeding line (NC84173, maternal and recurrent parent) and a salt-tolerant Lycopersicon pimpinellifolium accession (LA722). One hundred and nineteen BC1 individuals were genotyped for 151 RFLP markers and a linkage map was constructed. The parental lines and 119 BC1S1 families (self-pollinated progeny of the BC1 individuals) were evaluated for salt tolerance in aerated saline-solution cultures with the salt concentration gradually raised to 700 mM NaCl+70 mM CaCl2 (equivalent to an electrical conductivity of approximately 64 dS/m and a water potential of approximately −35.2 bars). The two parental lines were distinctly different in salt tolerance: 80% of the LA722 plants versus 25% of the NC84173 plants survived for at least 2 weeks after the final salt concentration was reached. The BC1S1 population exhibited a continuous variation, typical of quantitative traits, with the survival rate of the BC1S1 families ranging from 9% to 94% with a mean of 51%. Two QTL mapping techniques, interval mapping (using MAPMAKER/QTL) and single-marker analysis (using QGENE), were used to identify QTLs. The results of both methods were similar and five QTLs were identified on chromosomes 1 (two QTLs), 3, 5 and 9. Each QTL accounted for between 5.7% and 17.7%, with the combined effects (of all five QTLs) exceeding 46%, of the total phenotypic variation. All QTLs had the positive QTL alleles from the salt-tolerant parent. Across QTLs, the effects were mainly additive in nature. Digenic epistatic interactions were evident among several QTL-linked and QTL-unlinked markers. The overall results indicate that tomato salt tolerance during the vegetative stage could be improved by marker-assisted selection using interspecific variation.
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