Studies on biotic and abiotic elicitors inducing defense responses in tomato

Tomato (Lycopersicon esculentum Mill., Solanum lycopersicon L.) is one of the most popular vegetable throughout the world, and the importance of its cultivation is threatened by a wide array of pathogens. In the last twenty years this plant has been successfully used as a model plant to investigate the induction of defense pathways after exposure to fungal, bacterial and abiotic molecules, showing triggering of different mechanisms of resistance. Understanding these mechanisms in order to improve crop protection is a main goal for Plant Pathology. The aim of this study was to search for general or race-specific molecules able to determine in Solanum lycopersicon immune responses attributable to the main systems of plant defense: non-host, host-specific and induced resistance. Exopolysaccharides extracted by three fungal species (Aureobasidium pullulans, Cryphonectria parasitica and Epicoccum purpurascens), were able to induce transcription of pathogenesis-related (PR) proteins and accumulation of enzymes related to defense in tomato plants cv Money Maker,using the chemical inducer Bion® as a positive control. During the thesis, several Pseudomonas spp. strains were also isolated and tested for their antimicrobial activity and ability to produce antibiotics. Using as a positive control jasmonic acid, one of the selected strain was shown to induce a form of systemic resistance in tomato. Transcription of PRs and reduction of disease severity against the leaf pathogen Pseduomonas syringae pv. tomato was determined in tomato plants cv Money Maker and cv Perfect Peel, ensuring no direct contact between the selected rhizobacteria and the aerial part of the plant. To conclude this work, race-specific resistance of tomato against the leaf mold Cladosporium fulvum is also deepened, describing the project followed at the Phytopathology Laboratory of Wageningen (NL) in 2007, dealing with localization of a specific R-Avr interaction in transfected tomato protoplast cultures through fluorescence microscopy.

Diversified applications of supplemental LED light for greenhouse tomato production in the Mediterranean context

Among the various aspects to be investigated for a technological and productive upgrade of tomato greenhouse production in the Mediterranean area, the application of supplementary LED interlighting still shows limited interest. However, high-density tomato cultivation with intensive high-wire systems could lead to mutual shading and consequent reduction in photosynthesis and yield, even in case of appreciable amounts of external solar radiation, as in Southern Europe. Applications of interest could also involve off-season production or Building-Integrated Agriculture (BIA) such as rooftop greenhouses, where municipal regulations for structure and fire safety could limit the incoming radiation in the growing area. The aim of this research was to investigate diversified applications of supplemental LED interlighting for greenhouse tomato production (Solanum lycopersicum) in the Mediterranean countries. The diversified applications included: effects on post-harvest quality, shading reduction in BIA, tailored seedlings production, and off-season cultivation. The results showed that the application of supplemental LED light on greenhouse-grown tomato in Mediterranean countries (Italy and Spain) has potential to foster diverse applications. In particular, it can increase production in case of the limited solar radiation in rooftop greenhouses, maintain quality and reduce losses during post-harvest, help producing high quality and tailored seedlings, and increase yield during wintertime. Despite the positive results obtained, some aspects of the application of additional LED light in Southern Europe countries still need to be deepened and improved. In particular, given the current increase of electricity cost, future research should focus on more economically valuable methods of managing supplemental lighting, such as the application of shorter photoperiods or lower intensities, or techniques that can provide energy savings such as the pulsed light.