A reference map of Cucumis melo based on two recombinant inbred line populations

Abstract

A composite genetic melon map was generated based on two recombinant inbred line (RI) populations. By analyzing the segregation of 346 AFLPs, 113 IMAs and phenotypic characters on a RI population of 163 individuals derived from the cross Védrantais x PI 161375, a first map was constructed. About 20% of the molecular markers were skewed, and the residual heterozygosity was estimated at 4.43% which was not significantly different from the theoretical value of 4.2%. The genome distribution of molecular markers among the 12 linkage groups was not different from a random distribution with the exception of linkage group XII which was found significantly less populated. The genome distributions of IMAs and AFLPs were complementary. AFLPs were found mainly in the middle of each linkage group and sometimes clustered, whereas IMAs were found mainly at the end. A total of 318 molecular markers, mainly AFLP and IMA markers, were mapped on 63 RIs of the second population, Védrantais x PI 414723. Comparison of the maps enables one to conclude that AFLPs and IMAs of like molecular size, amplified with the same primer combination, correspond to the same genetic locus. Both maps were joined through 116 common markers comprising 106 comigrating AFLPs/IMAs, plus five SSRs and five phenotypic markers. The integrated melon map contained 668 loci issuing from the segregation of 1,093 molecular markers in the two RI populations. The composite map spanned 1,654 cM on 12 linkage groups which is the haploid number of chromosomes in melon. Thirty two known-function probes, i.e. known-function genes (9) and morphological traits (23), were included in this map. In addition, the composite map was anchored to previously published maps through SSRs, RFLPs and phenotypic characters.

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

“…PØrin et al (2002b) reported six FS QTLs in two populations of recombinant inbred lines. Comparing the position of the QTLs reported by those authors with the position presented in the current report and taking into account the co-linearity between both genetic maps (PØrin et al 2002a), it can be deduced that four QTLs have been detected in common: fs1.1, fs.5.1, fs6.1or fs6.2 and fs11.1 may correspond to fs8.1 or fs8.2, fs11.1, fs1.1 and fs12. 1, respectively, in PØrin et al (2002b).…”

“…Altogether, these data confirm that C. melo is one of the most diverse species of the genus Cucumis, although the genetic control of its phenotypic variation is largely unknown. Over 100 genes involved on morphological traits and disease resistance have been reported (Pitrat 1998), and 20 of them have been recently mapped (PØrin et al 2002a). These mapped genes should represent only a very small fraction of the genes underlying the phenotypic variation observed in melon germplasm.…”

“…Most of the variation could be due to a multiple allelic variability at a large number of quantitative trait loci (QTLs). Thorough analysis of QTLs requires detailed molecular marker linkage maps (Tanksley 1993), which are now being developed (Oliver et al 2001;PØrin et al 2002a), allowing the first reports of QTL analysis in melon. For example, PØrin et al (2002b) identified QTLs involved in fruit and flower shape using two recombinant inbred populations of melon.…”

Genetic Mapping and Molecular Breeding in Cucurbits

“…While Baudarcco-Arnas and Pitrat (1996) produced the first genetic map of melon with 102 RAPD and RFLP markers, this was quickly followed by Wang et al (1997) using 188 predominantly AFLP markers (Table 5.1). Using two RIL populations sharing one common parent, Périn et al (2002a) constructed a high-density composite map using co-migrating AFLP and IMA markers as anchor points. The composite map consists of 668 AFLP, IMA, and phenotypic markers.…”

“…Since cucurbit breeding places great emphasis on disease resistance, mapping populations used often segregated for more than one disease resistance gene. For example, in melon, MR-1 used by Wang et al (1997) was resistant to fusarium wilt (Fom-1 and Fom-2), downy and powdery mildews; Vedrantais and PI 161375 used by Baudarcco-Arnas and Pitrat (1996) and Périn et al (1998Périn et al ( , 2002a were resistant to fusarium wilt (Fom-1 and Fom-2), and melon necortic spot virus (nsv), and aphid (Vat), respectively; PI 161375 × Pinyonet Piel de Sapo used by Oliver et al (2001) segregated for both nsv and Vat . Populations used by Liou et al (1998), Fukino et al (2002, and Silberstein et al (2003) also segregated for disease resistance in addition to other horticultural traits.…”