Melon (Cucumis melo) is one of the principal vegetable crops for fresh market, for which a large number of breeding programs, oriented to generate inbred pure lines and hybrids, is established worldwide. The process to obtain and select these lines has been highly accelerated by the use of biotechnological techniques such as the generation of doubled haploid line (DHL) populations and molecular markers. Moreover, the use of DHLs in genetic studies is a useful tool because of their complete homozygosity and the permanent availability of plant material perpetuated by seed. In this work, the parthenogenetic response of 17 melon genotypes and the F1 hybrid PI 161375 × Spanish cultivar Piel de Sapo (PS) was studied considering three stages along the in vitro DHL generation process. The response of the analyzed melon cultivars was heterogeneous through the DHL generation with different limiting steps for each genotype. The response of the PI 161375 × PS hybrid was more similar to the male (PS) than the female parent (PI 161375), although the response of the maternal genotype was higher for some stages. This points to the important role of alleles from both parents in the different steps of the DHL generation process, and it could explain the identification of six genomic regions with distorted allelic segregation skewed toward PS or PI 161375. This hybrid was used to generate a population of 109 DHLs, the gametophytic origin of which was confirmed by flow cytometry and molecular markers.
Maria Jose Gonzalo, Elisabet Claveria, Antonio J. Monforte, and Ramon Dolcet-Sanjuan
Mónica Morales, Marisol Luís-Arteaga, José María Álvarez, Ramon Dolcet-Sanjuan, Amparo Monfort, Pere Arús, and Jordi Garcia-Mas
The recessive allele (nsv) of the NSV gene confers resistance to the Carmovirus melon necrotic spot virus (MNSV) in melon (Cucumis melo L.). Using an F2 population obtained from the cross between the resistant Korean accession PI 161375 and a susceptible line of `Piel de Sapo', we have mapped the NSV locus to linkage group 11 (G11) of the melon genome. Additional markers closely linked to NSV were developed by bulked segregant analysis (BSA) using a doubled haploid progeny population derived from the same cross. A detailed map of the NSV region was constructed containing 10 markers spanning a distance of 17.7 cM. The nearest flanking markers to NSV were two amplified fragment length polymorphisms (AFLPs) (CTA/ACG-115 and CTA/ACG-120) and one random amplified polymorphic DNA (RAPD) (OPD08-0.80) separated by 5.9 cM. Two more markers, ACC/ACC-110 and OPX15-1.06, cosegregated with NSV.