Genetics of Salt and Cold Tolerance in Tomato: Quantitative Analysis and QTL Mapping.

Abstract

Quantitative genetic analysis of tomato response to salt or cold stress during seed germination and vegetative growth indicated that both salt and cold tolerance were complex traits, controlled by more than one gene and highly influenced by environmental variation. Molecular marker analyses indicated that at each stage of plant development salt tolerance or cold tolerance was generally controlled by the effects of a few major QTLs (quantitative trait loci) which acted in concert with a number of smallereffect QTLs. At the seed germination stage, two types of QTLs were identified: those which affected germination under both stress and nonstress conditions, and thus were called stress-nonspecific QTLs, and those which contributed to rapid seed germination only under specific stress conditions, and thus were called stress-specific QTLs. Generally, the stress-nonspecific QTLs exhibited larger effects than the stress-specific QTLs. Consistent with this observation, selection for either salt or cold tolerance during germination resulted in progeny with improved germination under salt and cold stress as well as nonstress conditions. Comparison of salt tolerance during germination and vegetative growth indicated that mostly different QTLs contributed to tolerance at these two developmental stages; furthermore, selection for salt tolerance during germination did not affect progeny salt tolerance during vegetative growth. Similar results were obtained when cold tolerance during germination and vegetative growth were compared. The overall results indicate that, in tomato, stress tolerance during germination is independent of stress tolerance during vegetative growth. However, simultaneous improvement of plants for stress tolerance at multiple stages of plant development should be feasible through marker-assisted selection and breeding.

Relationship Between Cold Tolerance during Seed Germination and Vegetative Growth in Tomato: Analysis of Response and Correlated Response to Selection

“…However, it should be validated in other tomato germplasm before an unequivocal conclusion regarding this relationship can be drawn. Previously, by examining the response and correlated response to selection (Foolad and Lin, 1997) and by the comparison of the contributing QTLs (Foolad, 1999;Foolad and Lin, 1999a) we determined that, in different intraand interspecific populations of tomato, salt tolerance during seed germination was genetically independent of salt tolerance during vegetative growth. It is likely that this is also true for CT.…”

SSR Mapping of QTLs Conferring Cold Tolerance in an Interspecific Cross of Tomato

“…Walker et al found cold tolerance segregation in the BC 1 F 2 population from the cross of cultivated tomato and S. habrochaites by investigating the chlorophyll fluorescence [ 6 ]. Foolad et al also discovered the segregation in the BC 1 S 1 population derived from cultivated tomato and S. pimpinellifolium by investigating seed germination under low temperature [ 7 , 8 ].…”

Transformation of tomato with the BADH gene from Atriplex improves salt tolerance

“…Most of its cultivars are moderately sensitive to salt, with yield being seriously limited by the salinity of the soil or irrigating water (Cuartero and Munoz 1999;Foolad 1999). Extensive work has been done on breeding for enhanced tolerance to salinity and identifying quantitative trait loci-associated markers to enhanced tolerance and yield under stress.…”