Detection of QTL Controlling Fruit Size and Shape in Cucumis melo L.

Abstract

Mature fruit size and shape are important traits of most melon types. Our objective was to identify RAPD markers associated with major QTL affecting fruit weight, length, diameter and shape by means of bulked segregant analysis in an F2 population from the ananas melon cross of Deltex (larger fruit size) × TGR1551 (smaller fruit size). Clear separations for fruit weight, length, diameter, and shape between Deltex and TGR1551 were observed. Continuous distributions for fruit weight, length, diameter and shape were found in the F2 population indicating quantitative inheritance for the fruit traits. Significant positive correlations were detected between fruit weight and shape traits (r = 0.73 to 0.80). A significant positive correlation was observed between fruit weight and glucose (r = 0.35) or fructose (r = 0.25), whereas no correlation was noted between fruit weight and sucrose or total soluble solids. Two small and large bulks for fruit weight and shape were developed from F2 plants. A total of 240 primers were used to simultaneously screen between the small and large bulks, and between Deltex and TGR1551. Twenty-six RAPD markers were polymorphic for the small and large bulks. Ten markers were found to be significantly and consistently associated with fruit size and shape traits on the basis of simple linear regression. Of the 10 markers associated, four displayed an amplified DNA fragment in the small bulk, while six showed an amplified DNA fragment in the large bulk. The associated marker OJ07.350 explained 15% to 27% of the phenotypic variation for the fruit traits. These markers associated with QTL for melon fruit size and shape are expected to be useful in melon breeding programs for modifying fruit size.