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The global increasing demand of lettuce is pushing farmers to boost their production through several technical means, including mulching and nitrogen fertilization. However, from an environmental protection perspective, the role of scientific research is to limit the excessive use of some chemical approaches. This research aims to evaluate the possible effects of two mulching films (black polyethylene, PE, and brown photoselective film, BF) and two treatments with a plant growth-promoting product, containing Trichoderma spp., (non-treated, - Control and treated with RYZO PEP UP, - TR), on the productive and qualitative traits of lettuce grown under four regimes of nitrogen (0, 30, 60 and 90 kg ha&minus, 1, N0, N30, N60, and N90, respectively). The marketable yield increased at higher nitrogen levels, but without differences between the N60 and N90 doses. The photoselective film elicited marketable yield, with an 8% increase over PE. N fertilization also improved photochemical efficiency (higher Soil Plant Analysis Development and chlorophyllous pigments biosynthesis), as well as antioxidant activities (lipophilic&mdash, LAA and hydrophilic&mdash, HAA) and bioactive compounds (phenols and total ascorbic acid&mdash, TAA). Interestingly, Trichoderma spp. had a positive effect on these qualitative parameters, especially when combined with mulching films, where the increase generated by PE-TR treatment over the all other treatments was 16.3% and 16.8% for LAA and HHA, respectively. In all treatments, the nitrate leaves content was consistently always within the legal limit imposed by the European community. Overall, although Trichoderma spp. did not engender a marked effect on yield, probably due to the short crop cycle, its positive effect on some quality traits is an interesting starting point for further research.

Nitrogen is the primary technical means responsible for food production increase, but on the other hand, wise management is needed because its excessive use can have a negative impact on the environment and on green leafy vegetable quality, such as that rocket. Rocket has the characteristics of accumulating nitrate in leaves with possible impacts on human health. In order to overcome this issue, researchers are focusing their attention on the use of alternative means, such as plant biostimulant application. The scope of this study was to assess the effect of legume-derived protein hydrolysate(LDPH) and tropical plant extract(TPE), combined with various doses of nitrogen (0 kg ha&minus, 1 non-fertilized, N0), 60 kg ha&minus, 1 (sub-optimal, N1), 80 kg ha&minus, 1 (optimal, N2), and 100 kg ha&minus, 1 (supra-optimal, N3)), in order to reduce nitrogen use, boost yield, and enhance the chemical and nutritional value of leaves without significantly accumulating nitrate. Both vegetal-based plant biostimulants enhanced plant growth, boosted the marketable yield (especially at N0 and N1 levels, by 38.2% and 28.2%, respectively, compared to the non-treated control), and increased the SPAD (Soil Plant Analysis Development) index and leaf pigments content, such as chlorophyll and carotenoids, especially in treated-LDPH rocket. The plant-based biostimulants also produced a major amplification in lipophilic antioxidant activity (+ 48%) and total ascorbic acid content (average + 95.6%), especially at low nitrogen fertilization levels, and maintained nitrate content under the legal European Comission limits.

The present study investigated the transcriptomic and metabolomic changes elicited in tomato plants (Solanum lycopersicum cv. Micro-Tom) following treatments with the biocontrol agent T. harzianum strain M10 or its secondary metabolite harzianic acid (HA), in the presence or absence of the soil-borne pathogen Rhizoctonia solani. Transcriptomic analysis allowed the identification of differentially expressed genes (DEGs) that play a pivotal role in plant growth, development and resistance to biotic stress. Overall, the results support the ability of T. harzianum M10 to activate defense responses in infected tomato plants. We observed an induction of hormone-mediated signaling, as shown by the up-regulation of genes involved in the ethylene and jasmonate (ET/JA) biosynthesis. Further, the protective action of T. harzianum on the host was revealed by the over-expression of genes able to detoxify cells from reactive oxygen species (ROS). Moreover, the over-expression of genes involved in glycolysis, tricarboxylic acid cycle (TCA) and photosynthesis help to understand how this strain promotes plant growth and development. On the other hand, HA treatment also stimulated tomato response to the pathogen by inducing the expression of several genes involved in different defense mechanisms (including protease inhibitors, resistance proteins like CC-NBS-LRR) and activating ET/JA- and salicylic acid (SA)-mediated signaling pathways. The accumulation of steroidal glycoalkaloids caused by either T. harzianum or purified HA, as determined by metabolomic analysis, confirmed the complexity of the plant response to beneficial microbes in terms of secondary metabolism involved in defense mechanisms against pathogens.

Endophytic fungi have a great influence on plant health and growth, and are an important source of bioactive natural compounds. Organic extracts obtained from the culture filtrate of an endophytic strain of Talaromyces pinophilus isolated from strawberry tree (Arbutus unedo) were studied. Metabolomic analysis revealed the presence of three bioactive metabolites, the siderophore ferrirubin, the platelet-aggregation inhibitor herquline B and the antibiotic 3-O-methylfunicone. The latter was the major metabolite produced by this strain and displayed toxic effects against the pea aphid Acyrthosiphon pisum (Homoptera Aphidiidae). This toxicity represents an additional indication that the widespread endophytic occurrence of T. pinophilus may be related to a possible role in defensive mutualism. Moreover, the toxic activity on aphids could promote further study on 3-O-methylfunicone, or its derivatives, as an alternative to synthetic chemicals in agriculture.

Tomato is one of the most important vegetable crop worldwide with a total production of around 141 million tons on a cultivated area of around 5 million hectares (FAOSTAT, 2009, http://faostato.fao.org). Among the most representative countries, Italy contributes with more than 6 million tons to the world production, on a cultivated area of around 117.000 hectares, both in open fields and greenhouses (FAOSTAT, 2009). This crop represents also one of the major products of the food industry worldwide and Italy ranks first for processing tomato production among Countries of the Mediterranean Region (World Processing Tomato Council, 2009, www.wptc.to). Indeed, the high variability of tomato fruits, ranging from the cherry type to the big round or elongated berry, supplies both fresh market and processing products, such as paste, juice, sauce, powder or whole. In the last years, tomato consumption has further increased since it was demonstrated that tomato fruit could protect against diseases, such as cancer and cardiovascular disorders, due to its antioxidant properties (Rein et al., 2006). Tomato fruits are particularly rich of nutritional compounds such as lycopene and alfa-carotene, vitamin C, flavonoids and hydroxycinnamic acid derivatives whose intake would account for health benefits. The cultivated tomato (Solanum lycopersicum) belongs to the Solanaceae family that includes more than 3.000 species, among which 12 represent tomato wild relatives. These species exhibit a wide variety of adaptation to diverse habitats, plant morphology, fruit size and colour, the latter varying from green to white, yellow, pink, red, brown, depending mainly on the metabolites fruit content. The wild related tomato species represent a potential reservoir of useful genes that have been greatly used in breeding programs (Bai & Lindhout, 2007; Gur & Zamir, 2004). Indeed, this vegetable is one of the most investigated crop both at genetic and genomic level not only because of its economic importance but also because it is one of the best characterized plant systems. It has diploid genetics (24 somatic chromosomes), a small genome size (950 Mb per haploid nucleus), is self-pollinated, has a short generation time, is easily reproduced by seed and vegetative propagation and is crosscompatible with many wild species. All these characteristics make it amenable to genetic analysis.

In recent years, interest in tomato breeding for enhanced antioxidant content has increased as medical research has pointed to human health benefits from antioxidant dietary intake. Ascorbate is one of the major antioxidants present in tomato, and little is known about mechanisms governing ascorbate pool size in this fruit. In order to provide further insights into genetic mechanisms controlling ascorbate biosynthesis and accumulation in tomato, we investigated the fruit transcriptome profile of the Solanum pennellii introgression line 10-1 that exhibits a lower fruit ascorbate level than its cultivated parental genotype. Our results showed that this reduced ascorbate level is associated with an increased antioxidant demand arising from an accelerated oxidative metabolism mainly involving mitochondria, peroxisomes, and cytoplasm. Candidate genes for controlling ascorbate level in tomato fruit were identified, highlighting the role of glycolysis, glyoxylate metabolism, and purine breakdown in modulating the ascorbate pool size. Electronic supplementary material The online version of this article (doi:10.1007/s10528-012-9531-3) contains supplementary material, which is available to authorized users.

Background Tomato is an economically important crop with fruits that are a significant source of bioactive compounds such as ascorbic acid and phenolics. Nowadays, the majority of the enzymes of the biosynthetic pathways and of the structural genes controlling the production and the accumulation of antioxidants in plants are known; however, the mechanisms that regulate the expression of these genes are yet to be investigated. Here, we analyzed the transcriptomic changes occurring during ripening in the fruits of two tomato cultivars (E1 and E115), characterized by a different accumulation of antioxidants, in order to identify candidate genes potentially involved in the biosynthesis of ascorbic acid and phenylpropanoids. Results RNA sequencing analyses allowed identifying several structural and regulator genes putatively involved in ascorbate and phenylpropanoids biosynthesis in tomato fruits. Furthermore, transcription factors that may control antioxidants biosynthesis were identified through a weighted gene co-expression network analysis (WGCNA). Results obtained by RNA-seq and WGCNA analyses were further confirmed by RT-qPCR carried out at different ripening stages on ten cultivated tomato genotypes that accumulate different amount of bioactive compounds in the fruit. These analyses allowed us to identify one pectin methylesterase, which may affect the release of pectin-derived D-Galacturonic acid as metabolic precursor of ascorbate biosynthesis. Results reported in the present work allowed also identifying one L-ascorbate oxidase, which may favor the accumulation of reduced ascorbate in tomato fruits. Finally, the pivotal role of the enzymes chalcone synthases (CHS) in controlling the accumulation of phenolic compounds in cultivated tomato genotypes and the transcriptional control of the CHS genes exerted by Myb12 were confirmed. Conclusions By using transcriptomic analyses, candidate genes encoding transcription factors and structural genes were identified that may be involved in the accumulation of ascorbic acid and phenylpropanoids in tomato fruits of cultivated genotypes. These analyses provided novel insights into the molecular mechanisms controlling antioxidants accumulation in ripening tomato fruits. The structural genes and regulators here identified could also be used as efficient genetic markers for selecting high antioxidants tomato cultivars. Electronic supplementary material The online version of this article (10.1186/s12864-019-5428-4) contains supplementary material, which is available to authorized users.