Identification and Confirmation of RAPD Markers and Andromonoecious Associated with Quantitative Trait Loci for Sugars in Melon

Abstract

<jats:p>Our objectives were to identify randomly amplified polymorphic DNA (RAPD) markers associated with quantitative trait loci (QTL) for sucrose, total soluble solids (TSS), and sucrose percentage of total sugars (SPTS) using bulked segregant analysis in an F<jats:sub>2</jats:sub> population from the melon (<jats:italic>Cucumis melo</jats:italic> L.) cross of `TAM Dulce' (high sugars) × TGR1551 (low sugars) in a greenhouse experiment, and confirm the associations of RAPD markers with QTL for these sugar traits in an F<jats:sub>2</jats:sub> population from the different cross of `Deltex' (high sugars) × TGR1551 in a field experiment. Continuous distributions for sucrose, TSS, and SPTS were observed in the F<jats:sub>2</jats:sub> populations indicating quantitative inheritance for the traits. Significant positive correlations were found between sucrose and TSS or SPTS. Nine RAPD markers were detected to be significantly associated with QTL for sucrose in the F<jats:sub>2</jats:sub> population of the `TAM Dulce' × TGR1551 cross in the greenhouse based on simple linear regression. Five unlinked markers associated with QTL were significant in a stepwise multiple regression analysis where the full model explained 39% of the total phenotypic variation for sucrose. Five and seven of the nine RAPD markers associated with QTL for sucrose were also observed to be significantly associated with QTL for TSS and SPTS, respectively, suggesting that in this cross three sugar traits are controlled by the same QTL. Five RAPD markers were confirmed in the F<jats:sub>2</jats:sub> population of the `Deltex' × TGR1551 cross in the field to be consistently associated with QTL for three sugar traits. Significant associations of andromonoecious (<jats:italic>a</jats:italic>) with both sucrose and TSS were consistently expressed in our populations under greenhouse and field environments. These RAPD and floral markers associated with the sugar synthesis QTL identified and confirmed here could be useful in melon breeding for improving the mature fruit sweetness.</jats:p>

The Contribution of Sucrose Metabolism Enzymes to Sucrose Accumulation in Cucumis melo

“…Burger et al (2002) studied the inheritance of sucrose accumulation between the extreme low-sucrose genotype FAQ and the high-sucrose genotype NY, and reported that a major gene may determine the trait of sucrose accumulation. Other studies have generally indicated that sugar levels are a quantitative genetic trait (Sinclair et al, 2006). The difference may be explained by the choice of genetic material used.…”

A Genetic Linkage Map including Loci for Male Sterility, Sugars, and Ascorbic Acid in Melon

“…Five primers were tested in the three genotypes to survey the presence or absence of six markers to determine if the remaining LGs could be joined into regions of the composite map (Perin et al, 2002b). We also tested an additional nine primers in our population based on the conditions of Park et al (2004b) and Sinclair et al (2006) to map previously identified QTL for fruit quality traits and the ms-3 locus on the map.…”

“…Park et al (2004b) identified three RAPD and sequence characterized amplified region (SCAR) markers linked to the ms-3 locus for male sterility by means of bulked segregant analysis in an ms-3 • 'TAM Dulce' F 2 population. Eleven RAPD and andromonoecious (a) markers associated with muskmelon QTL for sugars were detected (Sinclair et al, 2006). They also reported nine RAPD markers associated with QTL for ascorbic acid.…”

“…Because consumers prefer sweet-tasting melons (Lester and Shellie, 1992), high soluble sugars (sucrose, fructose, and glucose) determine marketable grades (U.S. Government Printing Office, 1990). Therefore, improving sugar content is a significant goal in breeding programs worldwide (Sinclair et al, 2006).…”

“…An F 2 population of a 'Deltex' • TGR 1551 cross segregated for economically important traits including sugars, ascorbic acid, fruit size and shape, flesh and seed cavity size, seed size and quantity, and viral and fungal disease resistance (Alvarez et al, 2005;Lopez-Sese and Gomez-Guillamon, 2000;Park et al, 2007aPark et al, , 2007bPark et al, , 2007cSinclair et al, 2006). Some of these traits are not mapped on published linkage maps (Pitrat, 2005(Pitrat, -2006.…”