Identification and validation of QTLs for salt tolerance during vegetative growth in tomato by selective genotyping

Abstract

The purpose of this study was to identify quantitative trait loci (QTLs) for salt tolerance (ST) during vegetative growth (VG) in tomato by distributional extreme analysis and compare them with the QTLs previously identified for this trait. A BC1 population (N = 792) of a cross between a moderately salt-sensitive Lycopersicon esculentum Mill. breeding line (NC84173, maternal and recurrent parent) and a salt-tolerant L. pimpinellifolium (Jusl.) Mill. accession (LA722) was evaluated for ST in solution cultures containing 700 mM NaCl + 70 mM CaCl2 (electrical conductivity, EC = 64 dS/m and phiw approximately -35.2 bars). Thirty-seven BC1 plants (4.7% of the total) that exhibited the highest ST were selected (referred to as the selected population), grown to maturity in greenhouse pots and self-pollinated to produce BC1S1 progeny seeds. The 37 selected BC1S1 progeny families were evaluated for ST and their average performance was compared with that of the parental BC1 population before selection. A realized heritability of 0.50 was obtained for ST in this population. The 37 selected BC1 plants were subjected to restriction fragment length polymorphism (RFLP) analysis using 115 markers, and marker allele frequencies were determined. Allele frequencies for the same markers were also determined in an unselected BC1 population (N = 119) of the same cross. A trait-based marker analysis (TBA), which measures differences in marker allele frequencies between selected and unselected populations, was used to identify marker-linked QTLs. Five genomic regions were detected on chromosomes 1, 3, 5, 6, and 11 bearing significant QTLs for ST. Except for the QTL on chromosome 3, all QTLs had positive alleles contributed from the salt tolerant parent LA722. Of the five QTLs, three (those on chromosomes 1, 3, and 5) were previously identified for this trait in another study, and thus were validated here. Only one of the major QTLs that was identified in our previous study was not detected here. This high level of conformity between the results of the two studies indicates the genuine nature of the identified QTLs and their potential usefulness for ST breeding using marker-assisted selection (MAS). A few BC1S1 families were identified with most or all of the QTLs and with a ST comparable to that of LA722. These families should be useful for the development of salt tolerant tomato lines via MAS.

The Alleviation of the Adverse Effects of Salt Stress in the Tomato Plant by Salicylic Acid Shows A Time- and Organ-Specific Antioxidant Response

“…(2005) found that the most tolerant genotypes of S. lycopersicum could be characterized by increased K + /Na + ratios, carotenoid and sucrose contents and a reduced level of lipid peroxidation in the leaves during salt stress, suggesting a central role of the photosynthetic performance in the selection and breeding of cultivars for salt tolerance, though many genes and QTLs have also been described (Foolad et al, 2001;Cuartero et al, 2002).…”

Seedling salt tolerance in tomato

“…Co-localization of some QTLs for salt tolerance during seed germination and the seedling stage would strengthen the evidence that the same genes might control the rate of seed germination and seedling growth. Crosstalk for response to adverse abiotic and biotic stressors may share the common pathway, in which secondary metabolisms make a significant contribution (Chinnusamy et al Foolad et al 2001). Gray vertical bar indicate the approximate locations of QTLs previously identified from S. pennellii LA716 population for salt tolerance during seed germination (renamed as Stsgq) .…”

Towards salinity tolerance in Brassica: an overview

“…Rapid progress in molecular marker technology over the past few years has led to the development of detailed molecular linkage maps for many plant species (Jain and Selvaraj, 1997). The most important development in this regard is the discovery of DNAbased marker technology referred to as Marker Assisted (Tanksley et al, 1996;Foolad et al, 2001). The approach of QTL mapping has become crucial to the use of DNA markers in the improvement of crops species (Ramchiary e al., 2007).…”