Genetic Control of Fruit Vitamin C Contents
Uploaded by kmayzinbo on Jun 20, 2012
AbstractAn F1 progeny derived from a cross between the apple (Malus x domestica) cultivars Telamon and Braeburn was used to identify quantitative trait loci (QTL) linked to the vitamin C (l-ascorbate [l-AA]) contents of fruit skin and flesh (cortex) tissues. We identified up to three highly significant QTLs for both the mean l-AA and the mean total l-AA contents of fruit flesh on both parental genetic linkage maps, confirming the quantitative nature of these traits. These QTLs account for up to a maximum of 60% of the total population variation observed in the progeny, and with a maximal individual contribution of 31% per QTL. QTLs common to both parents were identified on linkage groups (LGs) 6, 10, and 11 of the Malus reference map, while each parent also had additional unique QTLs on other LGs. Interestingly, one strong QTL on LG-17 of the Telamon linkage map colocalized with a highly significant QTL associated with flesh browning, and a minor QTL for dehydroascorbate content, supporting earlier work that links fruit l-AA contents with the susceptibility of hardfruit to postharvest browning. We also found significant minor QTLs for skin l-AA and total l-AA (l-AA + dehydroascorbate) contents in Telamon. Currently, little is known about the genetic determinants underlying tissue l-AA homeostasis, but the presence of major, highly significant QTL in both these apple genotypes under field conditions suggests the existence of common control mechanisms, allelic heterozygosity, and helps outline strategies and the potential for the molecular breeding of these traits.
Vitamin C (l-ascorbic acid [l-AA]) is essential for all living plant tissues. Apart from well-known functions in oxidative stress defense, associated with its antioxidant properties and its abilities to detoxify reactive oxygen species, it also has important roles in the regulation of plant cell growth and expansion, photosynthesis, as well as hormone functions (for review, see Davey et al., 2000; Smirnoff, 2000). Even though nutritional deficiencies are rare in modern western cultures, it is generally recognized that dietary l-AA also has important health benefits for the consumer, and an increased intake of vitamin C has been associated with a decreased incidence of several important human diseases and disorders (Carr and Frei, 1999; Demmig-Adams and Adams, 2002; Hancock and Viola, 2005). Furthermore, in meat-poor diets, dietary l-AA can contribute to the improved uptake of iron and zinc, which are the major micronutrient deficiencies worldwide (Frossard et al., 2000). In apple (Malus x domestica) and...