Interaction between QTLs induces an advance in ethylene biosynthesis during melon fruit ripening

The coexistence of both climacteric and non-climacteric genotypes and the availability of a set of genetic and genomic resources make melon a suitable model for genetic studies of fruit ripening. We have previously described a QTL, ETHQB3.5, which induces climacteric fruit ripening in the near-isogenic line (NIL) SC3-5 that harbors an introgression on linkage group (LG) III from the non-climacteric melon accession PI 161375 in the, also non-climacteric cultivar, "Piel de Sapo" genetic background. In the current study, a new major QTL, ETHQV6.3, on LG VI was detected on an additional introgression in the same NIL. These QTLs are capable, individually, of inducing climacteric ripening in the non-climacteric background, the effects of ETHQV6.3 being greater than that of ETHQB3.5. The QTLs interact epistatically, advancing the timing of ethylene biosynthesis during ripening and, therefore, the climacteric responses. ETHQV6.3 was fine-mapped to a 4.5 Mb physical region of the melon genome, probably in the centromeric region of LG VI. The results presented will be of value in the molecular identification of the gene underlying ETHQV6.3.