Genetic dissection of fruit quality components in melon (Cucumis melo L.) using a RIL population derived from exotic × elite US Western Shipping germplasm

Growing environment dramatically influences melon (Cucumis melo L.; 2n = 2x = 24) fruit development and quality. Consequently, the characterization of quantitative trait loci (QTL) controlling melon fruit quality for application in marker-assisted selection (MAS) requires an assessment of genotype by environmental interactions, trait correlations, and QTL efficacy. Therefore, fruit quality traits [soluble solids content (SSC), mesocarp pressure (MP), fruit diameter (mesocarp + exocarp; FD), seed cavity diameter (endocarp; SCD), seed cavity to FD ratio (C:D), fruit shape (FS), and percentage of exocarp netting (PN) at time of harvest] were examined in 81 recombinant inbred lines (RIL) at two growing locations (California. and Wisconsin, USA) to identify the map position and consistency of QTL for MAS in a Group Cantalupensis U.S. Western Shipping market type background. RIL developed from a cross between U.S. Department of Agriculture line USDA-846-1 and ‘Top Mark’ were used to identify 57 QTL in both location tested (SSC = 10, MP = 8, FD = 6, SCD = 9, C:D = 8, PN = 6, and FS = 10). The QTL were distributed across 12 linkage groups and explained a significant portion of the associated phenotypic variation (R2 = 4–29%). Twelve of such QTL were consistently identified in the two locations tested [SSC (ssc7.4 and ssc10.8), MP (mp7.2, mp10.3, and mplg7.5), SCD (scd1.1, scd5.4, and scd8.5), C:D (cd2.1), and PN (pn2.1), FS (fs1.1 and fs2.3)]. The map positions of 18 QTL (FS = 7, SSC = 6, C:D = 3, SCD = 1, and PN = 1) were in equivalent (i.e., collinear) genomic regions with previous studies in Group Inodorus-based maps. Six of the collinear QTL were detected in both locations in our study (ssc7.4, ssc10.8, fs1.1, fs2.3, pn2.1, and scd5.4). The collinearity of these QTL with those identified in other maps, and their consistency across diverse growing environments portends their broad applicability in melon MAS.