17The influence of irrigation doses on standard and high lycopene tomato varieties has

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)....

Tomato yellow leaf curl virus (TYLCV) is a virus species causing epidemics in tomato (Solanum lycopersicum) worldwide. Many efforts have been focused on identification of resistance sources by screening wild tomato species. In many cases, the accession numbers were either not provided in publications or not provided in a consistent manner, which led to redundant screenings. In the current study, we summarized efforts on the screenings of wild tomato species for TYLCV resistance from various publications. In addition, we screened 708 accessions from 13 wild tomato species using different inoculation assays (i.e., whitefly natural infection and Agrobacterium-mediated inoculation) from which 138 accessions exhibited no tomato yellow leaf curl disease (TYLCD) symptoms. These symptomless accessions include 14 accessions from S. arcanum, 43 from S. chilense, 1 from S. chmielewskii, 28 from S. corneliomulleri, 5 from S. habrochaites, 4 from S. huaylasense, 2 from S. neorickii, 1 from S. pennellii, 39 from S. peruvianum, and 1 from S. pimpinellifolium. Most of the screened S. chilense accessions remained symptomless. Many symptomless accessions were also identified in S. arcanum, S. corneliomulleri, and S. peruvianum. A large number of S. pimpinellifolium accessions were screened. However, almost all of the tested accessions showed TYLCD symptoms. Further, we studied allelic variation of the Ty-1/Ty-3 gene in few S. chilense accessions by applying virus-induced gene silencing and allele mining, leading to identification of a number of allele-specific polymorphisms. Taken together, we present a comprehensive overview on TYLCV resistance and susceptibility in wild tomato germplasm, and demonstrate how to study allelic variants of the cloned Ty-genes in TYLCV-resistant accessions.

Since 1998 collapse of tomato plants has been producing significant losses in protected tomato crops along the Spanish Mediterranean coast. Affected plants show sudden and progressive wilt followed by total collapse and death. Analysis of the distribution and accumulation of Pepino mosaic virus (PepMV) in collapsed and non-collapsed plants and the presence of the virus in all analysed collapsed plants suggests a relationship of this Potexvirus with tomato collapse. The fact that collapse does not occur on PepMV-free farms reinforces this hypothesis. PepMV-infected plants showed a necrotic area in the vascular system, mainly in the basal area of the stem. This necrosis was more pronounced in collapsed plants and in the areas with higher viral concentration. Our hypothesis is that tomato collapse would be associated with necrosis of the vascular system caused by PepMV accumulation. Materials and Methods Analysis and incidence of collapsed plantsPlant analyses were carried out on the commercial hybrids cultivated in the south-eastern area of Spain, mainly Rambo F1, Durinta F1, Daniela F1 and Gabriela F1, which are resistant to some of the most www.blackwell-synergy.com

Tomato yellow leaf curl virus (TYLCV) hampers tomato production worldwide. Our previous studies have focussed on mapping and ultimately cloning of the TYLCV resistance genes Ty-1 and Ty-3. Both genes are derived from Solanum chilense and were shown to be allelic. They code for an RNA-dependent RNA polymerase (RDR) belonging to the RDRγ type defined by a DFDGD catalytic domain. In this study, we first fine-mapped the TYLCV resistance in S. chilense LA1932, LA1960 and LA1971. Results showed that chromosomal intervals of the causal genes in these TYLCV-resistant accessions overlap and cover the region where Ty-1/Ty-3 is located. Further, virus-induced gene silencing was used to silence Ty-1/Ty-3 in tomato lines carrying TYLCV resistance introgressed from S. chilense LA1932, LA1938 and LA1971. Results showed that silencing Ty-1/Ty-3 compromised the resistance in lines derived from S. chilense LA1932 and LA1938. The LA1971-derived material remained resistant upon silencing Ty-1/Ty-3. Further, we studied the allelic variation of the Ty-1/Ty-3 gene by examining cDNA sequences from nine S. chilense-derived lines/accessions and more than 80 tomato cultivars, landraces and accessions of related wild species. The DFDGD catalytic domain of the Ty-1/Ty-3 gene is conserved among all tomato lines and species analysed. In addition, the 12 base pair insertion at the 5-prime part of the Ty-1/Ty-3 gene was found not to be specific for the TYLCV resistance allele. However, compared with the susceptible ty-1 allele, the Ty-1/Ty-3 allele is characterized by three specific amino acids shared by seven TYLCV-resistant S. chilense accessions or derived lines. Thus, Ty-1/Ty-3-specific markers can be developed based on these polymorphisms. Elevated transcript levels were observed for all tested S. chilenseRDR alleles (both Ty-1 and ty-1 alleles), demonstrating that elevated expression level is not a good selection criterion for a functional Ty-1/Ty-3 allele.Electronic supplementary materialThe online version of this article (doi:10.1007/s11032-015-0329-y) contains supplementary material, which is available to authorized users.