Identification of quantitative trait loci involved in fruit quality traits in melon (Cucumis melo L.)

Abstract

Two populations [an F(2) and a set of 77 double haploid lines (DHLs)] developed from a cross between a 'Piel de Sapo' cultivar (PS) and the exotic Korean accession PI 161375 were used to detect QTLs involved in melon fruit quality traits: earliness (EA), fruit shape (FS), fruit weight (FW) and sugar content (SSC); and loci involved in the colour traits: external colour (ECOL) and flesh colour (FC). High variation was found, showing transgressive segregations for all traits. The highest correlation among experiments was observed for FS and the lowest for FW and SSC. Correlations among traits within experiments were, in general, not significant. QTL analysis, performed by Composite Interval Mapping, allowed the detection of nine QTLs for EA, eight for FS, six for FW and five for SSC. Major QTLs ( R(2)>25%) were detected for all traits. QTLs for different traits were no clearly co-localised, suggesting low pleiotropic effects at QTLs. Sixty-one per cent of them were detected in two or more experiments. QTLs for FS were detected in more trials than QTLs for FW and SSC, confirming that FS is under highly hereditable polygenic control. ECOL segregated as yellow:green in both experimental populations. The genetic control of ECOL was found to be complex, probably involving more than two loci with epistatic interactions. One of these loci was mapped on linkage group 9, but the other loci could not be clearly resolved. FC segregated as white:green:orange. The locus responsible for the green FC was mapped on linkage group 1, and it was proposed to correspond to the previously described locus gf. The genetic control of orange FC was complex: two loci in linkage groups 2 and 12 were associated with orange flesh, but larger population sizes would be necessary to elucidate completely the genetic control of orange flesh in this cross. Exotic alleles from PI161375 showed beneficial effects on EA, FW and SSC, indicating the usefulness of PI 161375 as a new source of genetic variability to improve European and American cultivars.

Analysis of the melon genome in regions encompassing TIR-NBS-LRR resistance genes

“…The double haploid lines (DHLs) from the melon genetic mapping population (Monforte et al 2004) were genotyped with these markers, allowing us to place the new markers on the melon genetic map.…”

Inheritance mode of fruit traits in melon: Heterosis for fruit shape and its correlation with genetic distance

“…Ovary and fruit shape are under a complex genetic control, sex type may be one of the factors affecting these traits. A number of QTLs independent from the sex type have been described recently (Périn et al, 2002;Monforte et al, 2004). The discrepancies between fruit shape and sex type may be due to different allelic combinations at several of these QTLs.…”

Genetic Mapping and Molecular Breeding in Cucurbits

“…Périn et al (2002c) also mapped QTLs for ethylene production in melon fruit (Table 5.3) and found one to be tightly linked to the melon ethylene receptor gene ERS1. Monforte et al (2004) evaluated F 2 cuttings and double-haploid lines from PI 161375 × Pinyonet Piel de Sapo in replicated field trials for earliness, fruit shape, fruit weight, sugar content, external color, and flesh color (Table 5.3). In agreement with Périn et al (2002b), they also found that fruit shape had the highest and fruit weight and sugar content the lowest heritability.…”