Cucurbits are major crop species, including fruits and vegetables cultivated worldwide that supply essential vitamins and minerals to current diets in developed and developing countries. Viral diseases are main factors affecting cucurbits cultivation. The most widespread and damaging have been aphidborne viruses belonging to the Potyviridae family. Whitefly-transmitted begomoviruses (Geminiviridae) have been identified more recently in different cucurbit species. A severe outbreak of Tomato leaf curl New Delhi virus (ToLCNDV) occurred in pumpkins and melons in the main production area of Southern Spain in 2012-2014. We developed a mechanical inoculation method to facilitate the screening of germplasm against this virus. Mechanical transmission with this method was confirmed in 4 genera and 13 species of the family, including the main crops, cucumber, melon, watermelon and pumpkins, and also croprelated exotic germplasm (landraces and wild species) used for cucurbits breeding. Diversity in the response was observed within and among species. Tolerance to mechanical transmission of ToLCNDV was identified in melon, within Cucumis melo subsp. agrestis var. momordica and in wild agrestis accessions. All the tolerant accessions came from India, the country in which this virus was firstly reported. Some of these accessions have been previously reported to be tolerant or resistant to other viruses and as they are fully crossable to commercial melons, they are good sources to develop new melon varieties with tolerance to ToLCNDV.

Background: There are few genomic tools available in melon (Cucumis melo L.), a member of the Cucurbitaceae, despite its importance as a crop. Among these tools, genetic maps have been constructed mainly using marker types such as simple sequence repeats (SSR), restriction fragment length polymorphisms (RFLP) and amplified fragment length polymorphisms (AFLP) in different mapping populations. There is a growing need for saturating the genetic map with single nucleotide polymorphisms (SNP), more amenable for high throughput analysis, especially if these markers are located in gene coding regions, to provide functional markers. Expressed sequence tags (ESTs) from melon are available in public databases, and resequencing ESTs or validating SNPs detected in silico are excellent ways to discover SNPs.

Our results highlight the huge amount of untapped aroma diversity of melon germplasm, especially of non-commercial types. Also, landraces with high nutritional value with regard to carotenoids have been identified. All this knowledge will encourage melon breeding, facilitating the selection of the genetic resources more appropriate to develop cultivars with new aromatic profiles or to minimize the impact of breeding on melon quality. The newly characterized sources provide the basis for further investigations into specific genes/alleles contributing to melon flesh quality. © 2018 Society of Chemical Industry.

BACKGROUNDThe grafting of watermelons (Citrullus lanatus) is a common technique that increases yields under stressful soil conditions. The most common rootstocks for watermelons are Cucurbita hybrids. However, they often have a negative impact on fruit quality.Exploiting novel Citrullus germplasm, such as citron melon (Citrullus lanatus var. citroides), is an alternative to avoid these quality problems. RESULTSCitron melon has been validated as watermelon rootstock, comparing its effects on watermelon quality to those of Cucurbita hybrids. Larger fruits with thicker rinds were observed in fruits from plants grafted onto both citron and Cucurbita rootstocks. The citron melon had no significant effect on flesh sugars or acid profiles compared to nongrafted watermelons, except for an increase in glucose and malic acid content, which also occurred in the Cucurbita rootstocks. The aroma profile of fruits produced onto citron melon was similar to that of the non-grafted and self-grafted controls. The citron rootstock didn't display the increased levels of (Z)-6-nonen-1-ol (a compound associated with pumpkin-like odors) found in fruits produced with Cucurbita hybrids. CONCLUSIONThe low impact of citron melon rootstock on fruit quality along with the enhanced resistance against nematodes, make the citron a promising alternative to Cucurbita rootstocks. KeywordsCitrullus lanatus; fruit quality; grafting; aroma profile This article is protected by copyright. All rights reserved. The most common commercial rootstocks for watermelons are Cucurbita interspecific hybrids (C. moschata Duchesne x C. maxima Duchesne) and bottle gourd accessions (Lagenaria siceraria Standl). These rootstocks confer resistance to most of the soilborne fungi affecting watermelon. However, they are susceptible to root-knot nematodes (RKN, Meloidogyne spp.). 4 These pathogens cause extensive damage to watermelon roots and increase the severity of Fusarium wilt in watermelon fields. RKNs used to be controlled in watermelon by fumigation with methyl bromide. However, the removal of methyl bromide from the markets has resulted in an increase of the impact of RKNs on watermelon and other cucurbit crops, as the alternative treatments are less effective than this fumigant. 5This situation has caused a spike in the search for resistances in other Cucurbitaceae genera that could lead to the development of alternative rootstock suitable for managing root-knot nematodes in watermelon crops. Some species belonging to the Cucumis A 5-cm cross section was obtained from the equatorial plane of each of four fruits per replication (sixteen fruits per treatment). Pericarp and approximately 2 mm of flesh and seeds were discarded. The remaining flesh was homogenized (KRUPS KB720, Groupe Seb Iberica, Barcelona, Spain) and kept frozen at -80ºC until metabolite analysis. Reagents for metabolite analysisOrganic acid standards were prepared from their sodium salts or free acids. The chemicals used were of analytical grade and were purchased from Sigma (St. Louis, MO, USA)....

Melon (Cucumis melo L.) ranks among the highest-valued fruit crops worldwide. Some genomic tools are available for this crop, including a Sanger transcriptome. We report the generation of 689,054 C. melo high-quality expressed sequence tags (ESTs) from two 454 sequencing runs, using normalized and nonnormalized complementary DNA (cDNA) libraries prepared from four genotypes belonging to the two C. melo subspecies and the main commercial types. 454 ESTs were combined with the Sanger available ESTs and de novo assembled into 53,252 unigenes. Over 63% of the unigenes were functionally annotated with Gene Ontology (GO) terms and 21% had known orthologs of Arabidopsis thaliana (L.) Heynh. Annotation distribution followed similar tendencies than that reported for Arabidopsis thaliana, suggesting that the dataset represents a fairly complete melon transcriptome. Furthermore, we identifi ed a set of 3298 unigenes with microsatellite motifs and 14,417 sequences with single nucleotide variants of which 11,655 single nucleotide polymorphism met criteria for use with high-throughput genotyping platforms, and 453 could be detected as cleaved amplifi ed polymorphic sequence (CAPS). A set of markers were validated, 90% of them being polymorphic in a number of variable C. melo accessions. This transcriptome provides an invaluable new tool for biological research, more so when it includes transcripts not described previously. It is being used for genome annotation and has provided a large collection of markers that will allow speeding up the process of breeding new melon varieties.