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Melon (Cucumis melo L.) production is often restricted by a plethora of pests and diseases, including powdery mildew and downy mildew caused respectively by the fungal species Podosphaera xanthii/Golovinomyces orontii and oomycete species Pseudoperonospora cubensis. Many efforts have been directed on identification of resistant sources by screening (wild) melon germplasm. In the current review, we summarized such efforts from various publications of the last 50 plus years. Resistance to powdery mildew has been identified in 239 melon accessions and downy mildew resistance in 452 accessions of both C. melo and the wild relative species C. figarei. Among the resistance sources, C. melo var. cantalupensis accessions PMR 45, PMR 5, PMR 6, and WMR 29 as well as C. melo var. momordica accessions PI 124111, PI 124112, and PI 414723 have been considered as the most valuable germplasm because multiple resistance genes have been identified from these accessions and are widely used in melon resistance breeding. Further genetic mapping in a number of resistant sources has enabled identification of 25 dominant genes, two recessive genes and seven QTLs conferring powdery mildew resistance, as well as eight dominant genes and 11 QTLs for downy mildew resistances. Based on the reported sequences of associated markers, we anchored physically (many of) these genes and QTLs to chromosomes of the melon cv. DHL92 genome. In addition to presenting a comprehensive overview on powdery mildew and downy mildew resistance in (wild) melon germplasm, we suggest strategies aiming at breeding melon with durable and broad-spectrum resistance to pathogens and pests.

Under field conditions, plants are often exposed to more than one stress factor at the same time, and therefore need to adapt to different combinations of stresses. Crosstalk between responses to abiotic and biotic stresses is known to occur, and the interaction between stress responses can be positive or negative. We studied the interaction of drought stress and powdery mildew (PM) infection in tomatoes using near-isogenic tomato lines (NILs) carrying the Ol-1, ol-2, or Ol-4 gene that confers resistance to tomato PM caused by Oidium neolycopersici. Our study demonstrated that drought-induced growth reduction was not further reduced by powdery mildew infection. Drought stress, however, decreased fungal infection in the susceptible genotype Moneymaker (MM) with fungal biomass tending to decrease further as the drought severity increased. Drought stress did not affect PM resistance levels of resistant NIL carrying ol-2 (a mutant of the tomato susceptibility Mlo gene) and Ol-4 an NLR (nucleotide-binding site-LRR) R gene associated with a fast hypersensitivity response (HR) but tended to slightly decrease disease levels of NIL-Ol-1 (no gene characterized yet, associated with a slow HR following PM infection). At the molecular level, genes involved in abscisic acid (ABA), salicylic acid (SA), and ethylene pathways were highly induced under combined stress indicating the involvement of ABA, SA, and ethylene in the crosstalk between abiotic and biotic stress. Messenger RNA expression of the ABA-responsive dehydrin SlTAS14 was induced under drought and combined stress with the highest induction under combined stress, and resistant NIL lines showed higher expression levels than MM. The expression of SlNCED (involved in ABA synthesis) was also upregulated under drought and highly induced under combined stress. Expression levels of pathogen responsive gene SlPR1 (an indicator of the SA pathway) and SlACS (involved in ethylene synthesis) were highly induced under powdery mildew infection in MM and the Ol-1 and were induced the most under combined stress in these lines. Taken together, these findings indicate that drought stress can interact with and influence PM infection in tomatoes in a resistance type-dependent manner. The role of hormonal signaling pathways in the crosstalk between drought stress and PM infection is further discussed.

Sterility of hybrids produced from interspecific hybridization in lilies (Lilium, Liliaceae) is a great limitation in the breeding program, especially for Lilium longiflorum, which only has white-flowered cultivars. Because modification of flower colour in L. longiflorum by conventional breeding is limited by pre- and post-fertilization barriers, we think genetic modification could be used as an alternative in the future. For this, we need to understand what determines white colouration in L. longiflorum and other species and identify the molecular mechanisms regulating flower colour. In this study, we determined the accumulation of anthocyanins and related compounds in flower tissues during flower developmental stages in L. longiflorum cultivar ‘Lincoln’ and in the Oriental hybrid lily cultivars ‘Rialto’, ‘Perth’ and ‘Gran Tourismo’, respectively with white, pink and red flowers. Furthermore, the presence/absence and the expression of eight structural genes (CHSa, CHSb, CHIa, CHIb, F3H, F3’H, DFR, ANS) and three transcription factor genes (MYB12, MYB15, bHLH2) in flower tissues were investigated. Two structural genes (LlLinF3’H and LlLinDFR) and one transcription factor gene (LlLinbHLH2) were not detected in ‘Lincoln’ flowers. In ‘Rialto’, an amino acid substitution in the R2 repeat of LhRiaMYB12 which was previously reported to be responsible for the white flower colour is also found in the LhPerMYB12 of the pink ‘Perth’ flowers. Moreover, LhRiaDFR is present but not expressed in ‘Rialto’ flowers. Accumulation of cyanidin was observed in the flowers of ‘Perth’ and ‘Gran Tourismo’. High amounts of dihydrokaempferol accumulated in flowers of all four lily cultivars confirming the expression and functionality of early structural genes in the pathway. The elevated expression of the structural genes is strongly correlated with the expression of LhMYB12 and LhMYB15. This information can be used in the future to generate new L. longiflorum or Oriental lily hybrid cultivars with novel flower colours.

We discuss options to reform the EU genetically modified organisms (GMO) regulatory framework, make risk assessment and decision-making more consistent with scientific principles, and lay the groundwork for international coherence. The first in a three-part series, this article focuses on reform options related to the scope of the legislation and the GMO definition.

The addition of far-red (FR, 700–800 nm) radiation to standard growth light triggers a set of photomorphogenic responses collectively termed shade avoidance syndrome. Recent research showed that additional FR increased fruit yield in greenhouse tomato production. However, the mechanism behind this increase is not clear; nor is it known whether there is a trade-off between growth and defense against plant diseases in tomato under additional FR. The aims of this study were 1) to quantify the effect of additional FR on tomato fruit growth, 2) to explain this effect based on underlying growth components and 3) to examine the FR effect on resistance against the necrotrophic fungus Botrytis cinerea. Tomato (Solanum lycopersicum ‘Moneymaker’) plants were grown for four months with 30 or 50 μmol m−2 s−1 of FR added to 150 μmol m−2 s−1 red + blue or white background LED lighting. Growth and development parameters were recorded, and a growth component analysis was conducted. Bioassays for resistance against B. cinerea were conducted on leaf samples collected from each light treatment. Additional FR increased total fruit dry mass per plant by 26–45%. FR affected multiple growth components, among which the fraction of dry mass partitioned to fruits was the most prominent with a 15–35% increase. Truss appearance rate was increased 11–14% by FR while instantaneous net photosynthesis rate was not affected. FR also resulted in more severe disease symptoms upon infection with B. cinerea. In conclusion, additional FR increases tomato fruit production mainly by increasing dry mass partitioning to fruits, rather than improving photosynthesis or increasing total plant biomass. However, FR also reduces resistance of tomato leaves against B. cinerea.

International audience; Is the European Union (EU) regulatory framework for genetically modified organisms (GMOs) adequate for emerging techniques, such as genome editing? This has been discussed extensively for more than 10 years. A recent proposal from The Netherlands offers a way to break the deadlock. Here, we discuss how the proposal would affect examples from public plant research.

In the original article, there was an incorrect formula. The formula appears in section 2.2.2, 'Linkage analysis in the presence of preferential chromosomal pairing', on page 3498. The correct formula is below in the context in which it appears. This gives rise to the likelihood function (Formula Presented) , which when solved leads to the following maximumlikelihood estimate for (Formula Presented). This has been corrected

Starch phosphate esters influence physiochemical properties of starch granules that are essential both for starch metabolism and industrial use of starches. To modify properties of potato starch and understand the effect of starch phosphorylation on starch metabolism in storage starch, the starch dikinases from Arabidopsis thaliana, glucan water dikinase 2 and 3 (AtGWD2 and AtGWD3), were heterologously expressed in potato tubers (Solanum tuberosum) from two genetic backgrounds: the amylose-containing clone Kardal and the amylose-free mutant amf. Modified starches showed altered granule morphology, but no significant changes in starch phosphate content were observed. Genes involved in starch metabolism did not show altered expression in the transgenic lines relatively to the control; however, sucrose synthase 4 (SUSY4) was upregulated in transgenic tubers with AtGWD2 expression. Taken together, these results demonstrated that expression of AtGWD2 and AtGWD3 are not suitable for engineering starch with a high phosphate content in potato tubers but can provide new insights in the process of starch phosphorylation in the amyloplast.

Unfortunately, in the original version of this article part of Fig. 1 was deleted in the final proofing step. The missing part of Fig. 1 with linkage groups 18–24.(Figure presented.).

In plants, tolerance to drought stress is a result of numerous minor effect loci in which transcriptional regulation contributes significantly to the observed phenotypes. Under severe drought conditions, a major expression quantitative trait loci hotspot was identified on chromosome five in potato. A putative Nuclear factor y subunit C4 was identified as key candidate in the regulatory cascade in response to drought. Further investigation of the eQTL hotspots suggests a role for a putative Homeobox leucine zipper protein 12 in relation to drought in potato. Genes strongly co-expressed with Homeobox leucine zipper protein 12 were plant growth regulators responsive to water deficit stress in Arabidopsis thaliana, implying a possible conserved mechanism. Integrative analysis of genetic, genomic, phenotypic and transcriptomic data provided insights in the downstream functional components of the drought response. The abscisic acid- and environmental stress-inducible protein TAS14 was highly induced by severe drought in potato and acts as a reliable biomarker for the level of stress perceived by the plant. The systems genetics approach supported a role for multiple genes responsive to severe drought stress of Solanum tuberosum. The combination of gene regulatory networks, expression quantitative trait loci mapping and phenotypic analysis proved useful for candidate gene selection.