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

Abstract

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.

Mapping and Introgression of QTL Involved in Fruit Shape Transgressive Segregation into ‘Piel de Sapo’ Melon (Cucucumis melo L.)

“…The effects of this allele seem to be masked by epistatic interactions with other gene(s) in the PI124112 background, and those effects were unveiled in the ‘PS’ background. A similar discovery has been reported recently with the obtaining of a climacteric line derived from the cross between two non-climateric melon accessions, ‘PS’ and ‘Shongwan Charmi’ [37]. This is a further indication of the richness of the melon gene pool that remains still largely unexplored.…”

“…In most cases, the strategy followed was the positional cloning, for what the availability of Near-Isogenic Lines (NILs) was essential, highlighting the importance of generating the appropriate genetic material to be successful. In this sense, the development of a collection of NILs in melon between the Korean cultivar ‘Songwhan Charmi’ and ‘PS’ [36] has allowed to dissect in single Mendelian factors economically important traits as fruit morphology [14], [17], climacteric ripening [37] and virus resistance [38].…”

Aroma volatiles obtained at harvest by HS‐SPME/GC‐MS and INDEX/MS‐E‐nose fingerprint discriminate climacteric behaviour in melon fruit

“…The different methodologies (GC‐MS or MS‐E‐nose) applied to analyse the headspace data revealed clear differences between aroma volatiles of the climacteric and aromatic NIL SC3‐5‐1 and those of the non‐climacteric and non‐aromatic PS parental. The NIL SC3‐5‐1 contains two QTLs of the climacteric behaviour in LG III and VI and, irrespective of the season, had a strong impact on the development of a full aroma (Fig. , and Table and Table ).…”

“…PS was tested as control. The introgressions of the PI 161375 in the genetic background of the parental line PS was located in two different linkage groups (LGs) (III and VI) by using molecular markers …”

“…The NIL SC3‐5‐1 is unique because it contains the two quantitative trait loci (QTLs) of the climacteric behaviour in melons . Knowing this, the main objective of this investigation was to compare two types of analytical method to characterise the most influential aroma volatile compounds responsible for the climacteric behaviour of SC3‐5‐1 compared with its non‐climacteric parental.…”