Daño al Proyecto de Vida

Youry Pii, Hannes Graf, Fabio Valentinuzzi, Stefano Cesco, Tanja Mimmo Faculty of Science and Technology, Free University of Bozen-Bolzano, Italy

Several studies have shown the benefits of plant growth-promoting rhizobacteria (PGPR) on plant mineral nutrition suggesting their application as biofertilizers. PGPR can stimulate plant growth, increase plant resistance to abiotic and biotic stresses and might thus have a positive effect also on fruit quality.

The aim of this work was therefore to evaluate and compare the effects of beneficial microorganisms, supplied either as pure culture (Azospirillum brasilense) or as a commercial mixture (Effective Microorganisms – EMTM_),

on the growth and quality of strawberry (Fragaria ananassa cv. Elsanta) fruits. Strawberries are in fact among the most popular fruits, because of their unique taste and health benefits for humans, due to a high content of micronutrients, phytochemicals and antioxidants.

Strawberry frigo-plants were hydroponically grown either in a complete nutrient solution, or in a nutrient solution inoculated with A. brasilense or with EM for 10 weeks (Pii et al., 2016). At harvest, biometric parameters, as shoot fresh weght, root fresh weight, and yield parameters, like number of fruits per plant and fruit weight, were recorded.

Growth parameter (e.g. biomass, leaf area) were not affected by the rhizoacteria. Even though PGPR- inoculated plants showed slightly reduced fruit yields in terms of average number of fruits/plant they delivered larger fruits as compared to controls. Fruits obtained from PGPR-inoculated plants had also a higher sweetness index in comparison to control fruits. The content of total phenols showed no significant difference between the different samples, whereas the concentration of flavonoids and flavonols was higher in fruits harvested from A. brasilense-inoculated plants. In addition, PGPRs also influenced the uptake and allocation of nutrients in fruits, in particular increasing the concentration of micronutrients (e.g. Fe).

In conclusion, our results demonstrate that the application of PGPR as biofertilizers might represent a sustainable agricultural practice to improve the nutraceutical value of strawberries, particularly concerning the content of flavonoids and micronutrients.

This work has been financially supported by the Free University of Bolzano (TN2023).

PT-PU-25 Ecological role of maytansine is revealed by in situ MALDI-HRMS-

imaging of Maytenus senegalensis during the germination process

Souvik Kusari, Dennis Eckelmann, Michael Spiteller

INFU, Department of Chemistry and Chemical Biology, Technische Universität Dortmund, Germany

MALDI-HRMS-imaging (matrix assisted laser desorption ionization high-resolution mass spectrometry imaging) is an important tool for visualizing, both spatially and temporally, metabolites at the interface of plants and microbes (e.g., endophytes and/or pathogens). Furthermore, the chemical communication between plant- associated microbes can be elucidated at the cellular level. We employed MALDI-HRMS imaging to study the ecological role of maytansine, an important anticancer drug used against breast cancer [1,2]. Since the discovery of maytansine in the 1970s in Celastraceae plants such as Maytenus and Putterlickia species, its role as a chemical defense compound was hypothesized [3]. After more than four decades of discovery of this important antineoplastic drug, we provide a proof-of-concept of ecospecific and tissue-specific production and

in situ spatial/temporal distribution of maytansine in Maytenus senegalensis plants. We have used MALDI- HRMS-imaging to visualize the occurrence and spatial/temporal distribution of maytansine in the leaves, stems, and roots of M. senegalensis plants, seeds obtained from the mother plants, through the germination process, and finally to the establishment of new seedlings or daughter plants. The mother plant was devoid of maytansine in all tissues. However, maytansine was produced and distributed in the cotyledons and the endosperm of the seeds with an augmented accretion towards the seed coat. Furthermore, maytansine was always detected in the emerging seedlings, particularly the cortex encompassing the radicle, hypocotyl, and epicotyl. The typical pattern of production and accumulation of maytansine not only in the seeds but also during germination provides evidence that M. senegalensis is ecologically primed to trigger the production of maytansine in vulnerable tissues such as seeds during plant reproduction. By utilizing maytansine as chemical defense compound against predators and/or pathogens, the plant can ensure viability of the seeds and successful germination, thus leading to the next generation of daughter plants with an evolutionary advantage of survival [4].

References: [1] Kusari et al. J. Nat. Prod., 2014, 77, 2577-2584; [2] Kusari et al. RSC Adv., 2016, 6, 10011-10016; [3] Kupchan et al. J. Am. Chem. Soc., 1972, 94, 1354-1356; [4] Eckelmann et al. Fitoterapia, 2017, 119, 51-56.

Poster Session 2: Plant understanding and improvement of beneficial interactions with microbes

PT-PU-26 Effects of structural and functional analogues of IAA in triggering

biological nitrogen fixation in non-legume plants

Anna Andrteozzi, Silvia Romano, Roberto Defez, Carmen Bianco

CNR, IBBR, Italy

We have verified that the endogenous overproduction of the main auxin indole-3-acetic acid (IAA) in diazotrophic endophytes isolated from rice plants led to a significant up-regulation of nitrogen fixation: the nifH

gene expression and the nitrogenase enzyme activity increased in both bacterial cultures and inoculated host plants as compared to the wild-type ones. When rice plants inoculated with wild type and IAA-overproducing nitrogen-fixing endophytes were compared significant changes in root morphology were observed: rice plants inoculate with the IAA-overproducing strains showed a more branched root system with abundant lateral root and significant changes in the primary root length. The aim of this work was to test the specificity of IAA effects on nitrogen-fixing apparatus in diazotrophic endophytes. Chemically or functionally similar molecules, such as indole (IND), indole-3-carboxylic acid (ICA), and 2,4-dichlorophenoxyacetic acid (2,4-D) were selected and exogenously added as purified substances into both liquid cultures and hydroponic systems of inoculated rice plants. Acetylene reduction assay (ARA) was carried out after treatment with the selected molecules. A significant increase of nitrogenase activity was measured only after the exogenous IAA-treatment in both conditions above described. This result leads us to say that the observed effect was specifically due to the hormonal activity of IAA. Studies to see if a similar effect can be obtained through co-infection of rice plants with nitrogen-fixing and IAA-producer endophytes are still underway. Selecting the best endophytic bacterial consortium could offer new perspectives to enhance nitrogen-fixation in non-legume crops.

PT-PU-27 How do phytohormones influence the composition of fungal endophyte

communities in tomato roots?

Andrea Manzotti, David B. Collinge, Hans Jørgen Lyngs Jørgensen, Birgit Jensen Plant and Environmental Sciences, University of Copenhagen, Denmark

Endophytes are microbes capable of colonizing the inner part of different plant tissues without causing disease symptoms. In some cases, they have beneficial effects for the host plant such as biotic and abiotic stress resistance and plant growth promotion. For this reason, the use of these microbes could have a major impact on agriculture worldwide. However, the plant-endophyte interaction involves very complex mechanisms starting from the recruitment of the microorganisms to the colonization of the surface of the plant tissue and then the inner part, with the need to escape the plant immune system. All these processes are regulated by different plant and endophyte signalling molecules necessary for the establishment of the plant-endophyte interaction. Phytohormones are among the signalling compounds known to play a significant role in this interaction, but little is known about the specific ways by which they influence recruitment and colonization of the host tissues. The aim of the current project is to go deeper into the role of these signalling compounds in plant-endophyte interactions.

A community analysis (endophyte isolation and amplicon sequencing) of endophytic fungi was conducted on roots of tomato (Solanum lycopersicum) mutants impaired in synthesis of specific phytohormones (specifically ethylene and jasmonic acid) in order to understand how these compounds influence the composition of the endophytic communities. After the characterization of the endophytic communities, fungal isolates whose root- colonization frequency appears to be influenced by the presence/absence of specific phytohormones were selected. In order to obtain a deeper understanding of the role of these compounds in the plant-endophyte interaction, the selected isolates are currently being screened by confocal microscopy and qPCR in order to identify candidates whose colonization rate is critically affected by the phytohormones of interest.

A transcriptomic analysis of tomato plants inoculated with the isolates selected from the screening will provide further clues as to which physiological mechanisms, associated with endophyte recruitment, are influenced by phytohormones.

Poster Session 2: Plant understanding and improvement of beneficial interactions with microbes

PT-PU-28 Effects of plant-growth-promoting rhizobacteria on barley under global

warming-associated environmental factors

Olga C. Calvo Alegre, Nwabufo Ndubuisi Chimelue, Andreas Fangmeier Institute of Landscape and Plant Ecology, Universität Hohenheim, Germany

Atmospheric concentration of CO2 is continuously increasing since the industrial revolution and may reach 550

ppm by the year 2050. Furthermore, given that environmental factors like CO2, temperature, and water

availability will likely change simultaneously, it is difficult to make accurate predictions about crop production under elevated CO2, reaching implications for food security. Plant-growth-promoting rhizobacteria (PGPR)

colonize the rhizosphere of many plant species and confer beneficial effects under environmental stresses. Furthermore, root exudates play a role in interactions between plant roots and other organisms present in the rhizosphere.

Only few reports have been published on PGPR as elicitors of tolerance to abiotic stresses, such as drought. Furthermore, little is known about the influence of environmental factors on root exudation patterns. Therefore, this study was conducted in order to investigate the effect of two commercially available PGPRs on the growth and root exudation of barley (Hordeum vulgare L.) under different CO2 and water treatments.

In a growth chamber experiment climatic conditions of a field site close to Stuttgart were simulated. Barley plants were grown in pots filled with sand and exposed to ambient (380 ppm) or elevated (550 ppm) CO2.

Plants received the normal daily amount of rainfall in the region of Stuttgart or 33% less. Plants were harvested at the stem elongation growth stage and when the inflorescences emerged. At both dates, data were collected on above and belowground variables. In addition, analyses of water use efficiency and composition of root exudates were performed. Preliminary results showed significant effects of the factors and their interactions on some of the measured variables.

In the context of climate change and agricultural sustainability, further studies with other crop plants are needed to demonstrate whether PGPR cause a range of crops to be tolerant to environmental stresses improving crop production.