2017 ASHS Annual Conference

The improvement of the root system is crucial for tomato (Solanum lycopersicum) to resist abiotic stresses, such as drought, salinity, and nutrient deficiency. However, very few investigations have addressed root traits as a breeding objective. Also, little knowledge of genetic control of root development in tomato is available. The objectives of this study were to identify quantitative trait loci (QTL) controlling root morphology and related shoot traits, and to investigate the relationships among them. We evaluated thirteen root and shoot traits of 187 F2 progeny derived from an advanced breeding line RvT1 (Solanum lycopersicum) and a wild species Lche4 (Solanum cheesmaniae). 1002 informative single nucleotide polymorphism (SNP) markers between parental lines were discovered using genotyping by sequencing (GBS). Among them, 742 SNP markers were successfully mapped and a medium-density linkage map was created, covering 1319.47 centiMorgan (cM) with an averaged distance of 1.78 cM between adjacent markers. In total, we identified 31 QTLs for the root and related shoot traits on chromosomes 1, 2, 3, 4, 6, 8, 9 and 11. The cultivated parent RvT1 contributed favorable alleles at two QTL hotspot regions on chromosomes 1 and 4. The QTL region on chromosome 1 governed root mass traits (root dry weight, root fresh weight and root to shoot ratio) and shoot traits (shoot length and chlorophyll content), while the one on chromosome 4 controlled root traits (root length, root surface area, root volume, root fresh weight and root dry weight). These two QTL regions were found to control various root and shoot traits, which were consistent with phenotypic correlation analysis. The wild parent Lche4 contributed favorable alleles at three QTLs on chromosomes 1 and 8 for specific root length, a trait associated with higher resource uptake rates, explaining 25.77% of the phenotypic variance. Markers flanking these QTLs could be useful to initiate a tomato breeding program to improve root systems, and assist us to develop advanced breeding lines in the future.