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Tomato is a major crop suffering substantial yield losses from diseases, as fruit decay at a postharvest level can claim up to 50% of the total production worldwide. Due to the environmental risks of fungicides, there is an increasing interest in exploiting plant immunity through priming, which is an adaptive strategy that improves plant defensive capacity by stimulating induced mechanisms. Broad-spectrum defence priming can be triggered by the compound ß-aminobutyric acid (BABA). In tomato plants, BABA induces resistance against various fungal and bacterial pathogens and different methods of application result in durable protection. Here, we demonstrate that the treatment of tomato plants with BABA resulted in a durable induced resistance in tomato fruit against Botrytis cinerea, Phytophthora infestans and Pseudomonas syringae. Targeted and untargeted metabolomics were used to investigate the metabolic regulations that underpin the priming of tomato fruit against pathogenic microbes that present different infection strategies. Metabolomic analyses revealed major changes after BABA treatment and after inoculation. Remarkably, primed responses seemed specific to the type of infection, rather than showing a common fingerprint of BABA-induced priming. Furthermore, top-down modelling from the detected metabolic markers allowed for the accurate prediction of the measured resistance to fruit pathogens and demonstrated that soluble sugars are essential to predict resistance to fruit pathogens. Altogether, our results demonstrate that metabolomics is particularly insightful for a better understanding of defence priming in fruit. Further experiments are underway in order to identify key metabolites that mediate broad-spectrum BABA-induced priming in tomato fruit.

Abstract: There is an urgent need in low cost and fast technologies that enable the exploration of natural or induced biodiversity in plants. Biochemical phenotyping is often considered as particularly promising to identify given analytes that are linked to desirable plant phenotypes and that could be used as markers for plant performance. Over the past 15 years, metabolomics and other omics approaches have been intensively used to study plant phenotypes. Still, they do not enable routine screens of very large populations in breeding programs, probably because this would represent unaffordable financial investments for equipment and specialised engineers. Along the last century, biochemical phenotyping and -screening have nevertheless been successfully exploited in medicine, pharmaceutical research and agro-industry. In medicine, over 6000 biochemical procedures exploiting a large variety of concepts and equipment are available for routine diagnosis and therapeutic monitoring. Pharmaceutical companies have spent massive investments to screen for biologically active molecules, whereas in the agro-industry increasingly sophisticated biochemical analysis has been developed to control the quality of raw and transformed products. Microplate technology is a well-established technology, which originated from the medical field and benefited from huge investments by the pharmaceutical industry. It offers the possibility to operate a wide range of analyses at very low costs per sample in plant research. To illustrate the potential of microplate technology as a high-throughput phenotyping tool, a screen for tomato metabolic mutants is shown where 24 enzymatic traits have been measured in more than 1500 samples within only 1 month with a relatively small investment. [Copyright &y& Elsevier]

The purpose of this study was to describe an unreported entomopathogenic fungus that naturally infects the cattle tick Rhipicephalus (Boophilus) microplus (Acari: Ixodidae). Engorged female ticks, showed symptoms of fungal infection after controlled tick infestation of cattle. Infected ticks developed a distinctive dark colour, a pale mould grew over the cuticle and the ticks eventually died covered with fungal conidiophores. The responsible fungus was isolated and cultured on mycological medium and submitted to microscopic morphology, biochemical phenotyping and 18S rRNA ribotyping analyses, which identified it as aflatoxin-producing Aspergillus flavus. Spores from the cultured fungus were experimentally sprayed over healthy engorged female ticks, obtaining an 80% prevalence of experimental infection of healthy ticks and their egg masses, the larval progeny after incubation under laboratory conditions was also infected. These results demonstrate that A. flavus is the causative agent of the natural fungal disease of the cattle tick R. microplus described here. [ABSTRACT FROM AUTHOR]

Tomato is a major crop suffering substantial yield losses from diseases, as fruit decay at a postharvest level can claim up to 50% of the total production worldwide. Due to the environmental risks of fungicides, there is an increasing interest in exploiting plant immunity through priming, which is an adaptive strategy that improves plant defensive capacity by stimulating induced mechanisms. Broad-spectrum defence priming can be triggered by the compound ß-aminobutyric acid (BABA). In tomato plants, BABA induces resistance against various fungal and bacterial pathogens and different methods of application result in durable protection. Here, we demonstrate that the treatment of tomato plants with BABA resulted in a durable induced resistance in tomato fruit against Botrytis cinerea, Phytophthora infestans and Pseudomonas syringae. Targeted and untargeted metabolomics were used to investigate the metabolic regulations that underpin the priming of tomato fruit against pathogenic microbes that present different infection strategies. Metabolomic analyses revealed major changes after BABA treatment and after inoculation. Remarkably, primed responses seemed specific to the type of infection, rather than showing a common fingerprint of BABA-induced priming. Furthermore, top-down modelling from the detected metabolic markers allowed for the accurate prediction of the measured resistance to fruit pathogens and demonstrated that soluble sugars are essential to predict resistance to fruit pathogens. Altogether, our results demonstrate that metabolomics is particularly insightful for a better understanding of defence priming in fruit. Further experiments are underway in order to identify key metabolites that mediate broad-spectrum BABA-induced priming in tomato fruit. [ABSTRACT FROM AUTHOR]

In comparison to the exponential increase of genotyping methods, phenotyping strategies are lagging behind in agricultural sciences. Genetic improvement depends upon the abundance of quantitative phenotypic data and the statistical partitioning of variance into environmental, genetic, and random effects. A metabolic phenotyping strategy was adapted to increase sample throughput while saving reagents, reducing cost, and simplifying data analysis. The chemical profiles of stem extracts from maize plants grown under low nitrogen (LN) or control trial (CT) were analyzed using optimized protocols for direct-injection electrospray ionization mass spectrometry (DIESI-MS). Specific ions significantly decreased or increased because of environmental (LN versus CT) or genotypic effects. Biochemical profiling with DIESI-MS had a superior cost-benefit compared to other standard analytical technologies (e.g., ultraviolet, near-infrared reflectance spectroscopy, high-performance liquid chromatography, and gas chromatography with flame ionization detection) routinely used for plant breeding. The method can be successfully applied in maize, strawberry, coffee, and other crop species.