Mapping of QTL Controlling Ananas Melon Fruit Net Formation

Melon (Cucumis melo L.) net formation traits are composed of net height, net width, and overall net coverage. Our objective was to identify RAPD and phenotypic markers linked to QTL controlling net height, net width, and overall net coverage in an F2 population from the cross of Deltex (net presence) x TGR1551 (net absence) grown in a greenhouse. These markers linked to QTL for net formation traits could then be placed in a genetic linkage map constructed using the F2 population of the cross. Continuous distributions for fruit net formation were observed in the population indicating quantitative inheritance for the traits. Net height was positively correlated with net width and overall net coverage. We also found a positive correlation of net width with overall net coverage. A total of 42 RAPD markers, 25 obtained from Deltex and 17 obtained from TGR1551, were identified to be significantly associated with QTL controlling net height in the population in the greenhouse based on simple linear regression and interval mapping. These markers explained 4% to 19% of the net height variation. Six markers associated with QTL on four linkage groups of the map were significant in a stepwise multiple regression analysis, and accounted for 42% of the total net height variation. Thirteen Deltex-derived markers on five linkage groups were significantly associated with QTL affecting net width in this population. Markers associated with five QTL explaining 24% of the total variation for net width were significant in the stepwise multiple regression analysis. Fourteen Deltex- and 13 TGR1551-derived markers were associated with QTL for overall net coverage in the population. Six markers on four linkage groups associated with QTL for overall net coverage were significant in the stepwise multiple regression analysis where the full model explained 31% of the total variation. Particularly, Deltex-derived markers OC14.1400 and OA09.300 on linkage group 7 were associated with all three net traits. These markers are expected to be useful in melon breeding for controlling fruit net formation.