Mapping of QTL Affecting Ascorbic Acid In Ananas Melon

Ascorbic acid, also known as vitamin C, is an important fruit quality trait in melon (Cucumis melo L.). Our objectives were to identify RAPD and andromonoecious (a) markers associated with QTL for ascorbic acid in an existing molecular linkage map constructed by means of an F2 greenhouse population from the Deltex (high ascorbic acid) x TGR1551 (low ascorbic acid) cross, and confirm the associations of RAPD and flower markers with QTL for the trait in an F2 field population from the same cross. Four markers on linkage groups 5 and 6 of the linkage map previously were reported to be associated with two Dulce-derived QTL for ascorbic acid. Thus, our additional goal was to determine the relationship of the Deltex- and Dulce-derived QTL to discern common and different QTL for ascorbic acid. A continuous distribution for ascorbic acid was observed in the greenhouse and field populations, indicating that the trait was quantitatively inherited. Ascorbic acid was positively correlated with sucrose and total soluble solids, whereas it was negatively correlated with glucose. A total of 29 RAPD and andromonoecious markers were found to be significantly associated with QTL affecting ascorbic acid in the greenhouse population based on simple linear regression. Fourteen markers were amplified from Deltex, while fifteen markers were obtained from TGR1551. Six markers associated with QTL on five linkage groups of the map were significant in a stepwise multiple regression analysis, and accounted for 30% of the total ascorbic acid variation. Sixteen RAPD markers were confirmed in the field population to be consistently associated with QTL for ascorbic acid. We found only one common Deltex- and Dulce-derived QTL for ascorbic acid on linkage group 5. These markers, along with an additional four Deltex- and three TGR1551-derived markers on linkage group 5, could be useful for marker-assisted selection to increase levels of ascorbic acid in new melon cultivars.