A physical map covering the nsv locus that confers resistance to Melon necrotic spot virus in melon (Cucumis melo L.)

Melon necrotic spot virus (MNSV) is a member of the genus Carmovirus, which produces severe yield losses in melon and cucumber crops. The nsv gene is the only known natural source of resistance against MNSV in melon, and confers protection against all widespread strains of this virus. nsv has been previously mapped in melon linkage group 11, in a region spanning 5.9 cM, saturated with RAPD and AFLP markers. To identify the nsv gene by positional cloning, we started construction of a high-resolution map for this locus. On the basis of the two mapping populations, F2 and BC1, which share the same resistant parent PI 161375 (nsv/nsv), and using more than 3,000 offspring, a high-resolution genetic map has been constructed in the region around the nsv locus, spanning 3.2 cM between CAPS markers M29 and M132. The availability of two melon BAC libraries allowed for screening and the identification of new markers closer to the resistance gene, by means of BAC-end sequencing and mapping. We constructed a BAC contig in this region and identified the marker 52K20sp6, which co-segregates with nsv in 408 F2 and 2.727 BC1 individuals in both mapping populations. We also identified a single 100 kb BAC that physically contains the resistance gene and covers a genetic distance of 0.73 cM between both BAC ends. These are the basis for the isolation of the nsv recessive-resistance gene.This work was partly funded by grants GEN2003-20237-C06-02 and AGL2003-02739 from the Spanish ‘Ministerio de Ciencia y Tecnología’.Peer reviewe

A consensus linkage map for molecular markers and Quantitative Trait Loci associated with economically important traits in melon (Cucumis melo L.)

Background A number of molecular marker linkage maps have been developed for melon (Cucumis melo L.) over the last two decades. However, these maps were constructed using different marker sets, thus, making comparative analysis among maps difficult. In order to solve this problem, a consensus genetic map in melon was constructed using primarily highly transferable anchor markers that have broad potential use for mapping, synteny, and comparative quantitative trait loci (QTL) analysis, increasing breeding effectiveness and efficiency via marker-assisted selection (MAS). Results Under the framework of the International Cucurbit Genomics Initiative (ICuGI, http://www.icugi.org webcite), an integrated genetic map has been constructed by merging data from eight independent mapping experiments using a genetically diverse array of parental lines. The consensus map spans 1150 cM across the 12 melon linkage groups and is composed of 1592 markers (640 SSRs, 330 SNPs, 252 AFLPs, 239 RFLPs, 89 RAPDs, 15 IMAs, 16 indels and 11 morphological traits) with a mean marker density of 0.72 cM/marker. One hundred and ninety-six of these markers (157 SSRs, 32 SNPs, 6 indels and 1 RAPD) were newly developed, mapped or provided by industry representatives as released markers, including 27 SNPs and 5 indels from genes involved in the organic acid metabolism and transport, and 58 EST-SSRs. Additionally, 85 of 822 SSR markers contributed by Syngenta Seeds were included in the integrated map. In addition, 370 QTL controlling 62 traits from 18 previously reported mapping experiments using genetically diverse parental genotypes were also integrated into the consensus map. Some QTL associated with economically important traits detected in separate studies mapped to similar genomic positions. For example, independently identified QTL controlling fruit shape were mapped on similar genomic positions, suggesting that such QTL are possibly responsible for the phenotypic variability observed for this trait in a broad array of melon germplasm. Conclusions Even though relatively unsaturated genetic maps in a diverse set of melon market types have been published, the integrated saturated map presented herein should be considered the initial reference map for melon. Most of the mapped markers contained in the reference map are polymorphic in diverse collection of germplasm, and thus are potentially transferrable to a broad array of genetic experimentation (e.g., integration of physical and genetic maps, colinearity analysis, map-based gene cloning, epistasis dissection, and marker-assisted selection).This work was supported in part by SNC Laboratoire ASL, Ruiter Seeds B.V., Enza Zaden B.V., Gautier Semences S.A., Nunhems B.V., Rijk Zwaan B.V., Sakata Seed Inc, Semillas Fito S. A., Seminis Vegetable Seeds Inc, Syngenta Seeds B. V., Takii and Company Ltd, Vilmorin & Cie S. A., and Zeraim Gedera Ltd (all of them as part of the support to the ICuGI); the grants AGL2009-12698-C02-02 from the Spanish "Ministerio de Ciencia e Innovacion" to AJM. NK lab was supported in part by Research Grant Award No. IS-4223-09C from BARD, the United States - Israel Binational Agricultural Research and Development Fund, and in part by Israel Science Foundation Grant No. 38606, De Ruiter Seeds, Enza Zaden, Keygene, Rijk Zwaan, Sakata Seed Corporation, Semillas Fito, Syngenta Seeds and Vilmorin Clause & Cie. AD was supported by a JAE-Doc contract from "Consejo Superior de Investigaciones Cientificas" (CSIC-Spain). MF was supported by a postdoctoral contract from CRAG. The research carried out at YX's laboratory was supported by Chinese funds (Grant No. 2008-Z42(3), 5100001, 2010AA101907).Díaz Bermúdez, A.; Fergany, M.; Formisano, G.; Ziarsolo, P.; Blanca Postigo, JM.; Fei, Z.; Staub, JE.... (2011). A consensus linkage map for molecular markers and Quantitative Trait Loci associated with economically important traits in melon. BMC Plant Biology. 11. https://doi.org/10.1186/1471-2229-11-111S1

A comprehensive genome variation map of melon identifies multiple domestication events and loci influencing agronomic traits

Melon is an economically important fruit crop that has been cultivated for thousands of years; however, the genetic basis and history of its domestication still remain largely unknown. Here we report a comprehensive map of the genomic variation in melon derived from the resequencing of 1,175 accessions, which represent the global diversity of the species. Our results suggest that three independent domestication events occurred in melon, two in India and one in Africa. We detected two independent sets of domestication sweeps, resulting in diverse characteristics of the two subspecies melo and agrestis during melon breeding. Genome-wide association studies for 16 agronomic traits identified 208 loci significantly associated with fruit mass, quality and morphological characters. This study sheds light on the domestication history of melon and provides a valuable resource for genomics-assisted breeding of this important crop.info:eu-repo/semantics/acceptedVersio

A comprehensive genome variation map of melon identifies multiple domestication events and loci influencing agronomic traits

Melon is an economically important fruit crop that has been cultivated for thousands of years; however, the genetic basis and history of its domestication still remain largely unknown. Here we report a comprehensive map of the genomic variation in melon derived from the resequencing of 1,175 accessions, which represent the global diversity of the species. Our results suggest that three independent domestication events occurred in melon, two in India and one in Africa. We detected two independent sets of domestication sweeps, resulting in diverse characteristics of the two subspecies melo and agrestis during melon breeding. Genome-wide association studies for 16 agronomic traits identified 208 loci significantly associated with fruit mass, quality and morphological characters. This study sheds light on the domestication history of melon and provides a valuable resource for genomics-assisted breeding of this important crop.This work was supported by funding from the Agricultural Science and Technology Innovation Program (to Yongyang Xu, S.H., Z.Z. and H.W.), the China Agriculture Research System (CARS-25 to Yongyang Xu and H.W.), the Leading Talents of Guangdong Province Program (00201515 to S.H.), the Shenzhen Municipal (The Peacock Plan KQTD2016113010482651 to S.H.), the Dapeng district government, National Natural Science Foundation of China (31772304 to Z.Z.), the Science and Technology Program of Guangdong (2018B020202007 to S.H.), the National Natural Science Foundation of China (31530066 to S.H.), the National Key R&D Program of China (2016YFD0101007 to S.H.), USDA National Institute of Food and Agriculture Specialty Crop Research Initiative (2015-51181-24285 to Z.F.), the European Research Council (ERC-SEXYPARTH to A.B.), the Spanish Ministry of Economy and Competitiveness (AGL2015–64625-C2-1-R to J.G.-M.), Severo Ochoa Programme for Centres of Excellence in R&D 2016–2010 (SEV-2015–0533 to J.G.-M.), the CERCA Programme/Generalitat de Catalunya to J.G.-M. and the German Science Foundation (SPP1991 Taxon-OMICS to H.S.)

Engineering Melon Plants with Improved Fruit Shelf Life Using the TILLING Approach

Background: Fruit ripening and softening are key traits that have an effect on food supply, fruit nutritional value and consequently, human health. Since ethylene induces ripening of climacteric fruit, it is one of the main targets to control fruit over ripening that leads to fruit softening and deterioration. The characterization of the ethylene pathway in Arabidopsis and tomato identified key genes that control fruit ripening. [br/] Methodology/Principal Findings: To engineer melon fruit with improved shelf-life, we conducted a translational research experiment. We set up a TILLING platform in a monoecious and climacteric melon line, cloned genes that control ethylene production and screened for induced mutations that lead to fruits with enhanced shelf life. Two missense mutations, L124F and G194D, of the ethylene biosynthetic enzyme, ACC oxidase 1, were identified and the mutant plants were characterized with respect to fruit maturation. The L124F mutation is a conservative mutation occurring away from the enzyme active site and thus was predicted to not affect ethylene production and thus fruit ripening. In contrast, G194D modification occurs in a highly conserved amino acid position predicted, by crystallographic analysis, to affect the enzymatic activity. Phenotypic analysis of the G194D mutant fruit showed complete delayed ripening and yellowing with improved shelf life and, as predicted, the L124F mutation did not have an effect. [br/] Conclusions/Significance: We constructed a mutant collection of 4023 melon M2 families. Based on the TILLING of 11 genes, we calculated the overall mutation rate of one mutation every 573 kb and identified 8 alleles per tilled kilobase. We also identified a TILLING mutant with enhanced fruit shelf life. This work demonstrates the effectiveness of TILLING as a reverse genetics tool to improve crop species. As cucurbits are model species in different areas of plant biology, we anticipate that the developed tool will be widely exploited by the scientific community

The quasi-universality of nestedness in the structure of quantitative plant-parasite interactions

Understanding the relationships between host range and pathogenicity for parasites, and between the efficiency and scope of immunity for hosts are essential to implement efficient disease control strategies. In the case of plant parasites, most studies have focused on describing qualitative interactions and a variety of genetic and evolutionary models has been proposed in this context. Although plant quantitative resistance benefits from advantages in terms of durability, we presently lack models that account for quantitative interactions between plants and their parasites and the evolution of these interactions. Nestedness and modularity are important features to unravel the overall structure of host-parasite interaction matrices. Here, we analysed these two features on 32 matrices of quantitative pathogenicity trait data gathered from 15 plant-parasite pathosystems consisting of either annual or perennial plants along with fungi or oomycetes, bacteria, nematodes, insects and viruses. The performance of several nestedness and modularity algorithms was evaluated through a simulation approach, which helped interpretation of the results. We observed significant modularity in only six of the 32 matrices, with two or three modules detected. For three of these matrices, modules could be related to resistance quantitative trait loci present in the host. In contrast, we found high and significant nestedness in 30 of the 32 matrices. Nestedness was linked to other properties of plant-parasite interactions. First, pathogenicity trait values were explained in majority by a parasite strain effect and a plant accession effect, with no parasite-plant interaction term. Second, correlations between the efficiency and scope of the resistance of plant genotypes, and between the host range breadth and pathogenicity level of parasite strains were overall positive. This latter result questions the efficiency of strategies based on the deployment of several genetically-differentiated cultivars of a given crop species in the case of quantitative plant immunity

Insect resistance in melon and its modification by molecular breeding

absen

Association between Aphis gossypii genotype and phenotype on melon accessions

Development of molecular markers has allowed the characterization of several host–aphid interactions. We investigated the usefulness of microsatellite markers to characterize the plant resistance interaction in the model Aphis gossypii/Cucumis melo. Six aphid clones, collected in different localities and years and belonging to two multilocus genotypes (MLGs) based on eight microsatellite markers, were phenotyped on a set of 33 melon accessions, some of them known to carry the Vat gene. Three parameters were used: acceptance of plant, ability to colonize the plant and resistance to virus when inoculated by aphids. Concordance and correlation analyses showed that aphid clones sharing a same MLG exhibited a very agreeable phenotype on the set of accessions for acceptance of plant and resistance to virus when inoculated by aphids. From host point of view, melon accessions were grouped into four clear categories, resistant to aphids of both MLGs, only resistant to the NM1 MLG, only resistant to the C9 MLG, susceptible to both MLGs and another group of unclear characteristics. The four categories revealed different patterns of virulence for NM1 and C9 MLGs that are likely controlled by a single avirulence gene in accordance with a gene for gene interaction. In contrast, the ability to colonize the plant appeared slightly variable among clones sharing a same MLG. We hypothesize it is due to the putative polygenic control of this aphid trait. Because the phenotypic variability of A. gossypii matched the genetic variability revealed by eight microsatellite markers, these markers could be used to infer the frequency of biotypes in field experiments and help to elucidate the allele diversity of melon resistance gene

The battle for survival between viruses and their host plants

International audienceEvolution has equipped plants with defense mechanisms to counterattack virus infections. However, some viruses have acquired the capacity to escape these defense barriers. In their combats, plants use mechanisms such as antiviral RNA silencing that viruses fight against using silencing-repressors. Plants could also resist by mutating a host factor required by the virus to complete a particular step of its infectious cycle. Another successful mechanism of resistance is the hypersensitive response, where plants engineer R genes that recognize specifically their assailants. The recognition is followed by the triggering of a broad spectrum resistance. New understanding of such resistance mechanisms will probably helps to propose new means to enhance plant resistance against viruses