Candidate Genes and Quantitative Trait Loci Affecting Fruit Ascorbic Acid Content in Three Tomato Populations

Abstract

Fresh fruit and vegetables are a major source of ascorbic acid (vitamin C), an important antioxidant for the human diet and also for plants. Ascorbic acid content in fruit exhibits a quantitative inheritance. Quantitative trait loci (QTL) for ascorbic acid content have been mapped in three tomato populations derived from crosses between cultivated tomato varieties (Solanum lycopersicum accessions) and three related wild species or subspecies. The first population consists of a set of introgression lines derived from Solanum pennellii, each containing a unique fragment of the wild species genome. The second population is an advanced backcross population derived from a cross between a cultivated tomato and a Solanum habrochaites (formerly Lycopersicum hirsutum) accession. The third population is a recombinant inbred line population derived from the cross between a cherry tomato line and a large fruited line. Common regions controlling ascorbic acid content have been identified on chromosomes 2, 8, 9, 10, and 12. In general, the wild alleles increased ascorbic acid content, but some improvement could also be provided by S. lycopersicum. Most QTLs appeared relatively stable over years and in different environments. Mapping of candidate genes involved in the metabolism of ascorbic acid has revealed a few colocations between genes and QTLs, notably in the case of a monodehydroascorbate reductase gene and a QTL present in two of the populations on chromosome 9 (bin 9-D), and a previously mapped GDP-mannose epimerase and a QTL on chromosome 9 (bin 9-J).

Genome-Wide Association in Tomato Reveals 44 Candidate Loci for Fruit Metabolic Traits

“…For example, the most significant differences (P , 1 3 10 29 ) were observed for ascorbate and dehydroascorbate levels or SSC with higher levels in S.P compared with S.C and S.L. This was previously observed through the detection of QTLs related to ascorbate levels (Stevens et al, 2007) and related to SSC (Prudent et al, 2009) as well as through GWA for SSC (Xu et al, 2013).…”

“…Over the last two decades, numerous QTLs have been identified for traits such as fresh weight using linkage approaches (Frary et al, 2000;Zhang et al, 2012;Chakrabarti et al, 2013) but also for other fruit-related traits such as fruit ascorbic acid levels (Stevens et al, 2007), sensory and instrumental quality traits (Causse et al, 2002), sugar and organic acids (Fulton et al, 2002), and metabolic components (Schauer et al, 2008). Large tomato germplasm collections have been characterized at the molecular level using simple sequence repeat (Ranc et al, 2008) and single-nucleotide polymorphism (SNP) markers (Blanca et al, 2012;Shirasawa et al, 2013), giving insights into population structure, tomato evolutionary history, and the genetic architecture of traits of agronomic interest.…”

Allelic Variation in Paralogs of GDP-l-Galactose Phosphorylase Is a Major Determinant of Vitamin C Concentrations in Apple Fruit

“…In tomato, an ortholog of MDHAR (SlMDHAR3) has been found to colocate with a stable QTL for fruit AsA contents (Stevens et al, 2007), and MDHAR enzyme activity has been associated with elevated AsA concentrations under chilling stress (Stevens et al, 2008). In apple, we found no colocation between MdMDHARs and any antioxidant QTL.…”

“…In tomato (Ioannidi et al, 2009) and kiwifruit (Bulley et al, 2009), fruit AsA concentrations were also not correlated with GMP expression. GME has been proposed to be critical for the regulation of plant AsA concentrations by several groups (Wolucka and Van Montagu, 2007;Gilbert et al, 2009), and in tomato, SlGME1 colocates with a cluster of stable fruit AsA-QTL (Stevens et al, 2007), while in apple, MdGME transcript levels are highly correlated with AsA concentrations during apple fruit development (Li et al, 2011). However, the data presented here support the results obtained in peach (Prunus persica; Imai et al, 2009) and tomato (Ioannidi et al, 2009), which suggest that this step is not a major point of control in mature apple fruit, at least under our field conditions.…”

“…Genes involved in several of these mechanisms have been proposed to be key regulators of fruit AsA concentrations, including GDP-L-Gal phosphorylase (GGP) or vitamin c defective2 (VTC2) in kiwifruit (Actinidia deliciosa; Bulley et al, 2009Bulley et al, , 2012 as well as GDP-Man-3,5-epimerase (GME; Gilbert et al, 2009), L-Gal-1-Pphosphatase (GPP or VTC4; Ioannidi et al, 2009), and MDHAR (Stevens et al, 2007) in tomato. However, apart from GGP (Bulley et al, 2012), overexpression of these structural genes has to date had limited success in altering the fruit AsA pool (Agius et al, 2003;Bulley et al, 2009;Haroldsen et al, 2011).…”