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Introduction: Artemisinin is a secondary metabolite well-known for its use in the treatment of malaria. It also displays other antimicrobial activities which further increase its interest. At present, Artemisia annua is the sole commercial source of the substance, and its production is limited, leading to a global deficit in supply. Furthermore, the cultivation of A. annua is being threatened by climate change. Specifically, drought stress is a major concern for plant development and productivity, but, on the other hand, moderate stress levels can elicit the production of secondary metabolites, with a putative synergistic interaction with elicitors such as chitosan oligosaccharides (COS). Therefore, the development of strategies to increase yield has prompted much interest. With this aim, the effects on artemisinin production under drought stress and treatment with COS, as well as physiological changes in A. annua plants are presented in this study. Methods: Plants were separated into two groups, well-watered (WW) and drought-stressed (DS) plants, and in each group, four concentrations of COS were applied (0, 50,100 and 200 mg•L-1). Afterwards, water stress was imposed by withholding irrigation for 9 days. Results: Therefore, when A. annua was well watered, COS did not improve plant growth, and the upregulation of antioxidant enzymes hindered the production of artemisinin. On the other hand, during drought stress, COS treatment did not alleviate the decline in growth at any concentration tested. However, higher doses improved the water status since leaf water potential (YL) improved by 50.64% and relative water content (RWC) by 33.84% compared to DS plants without COS treatment. Moreover, the combination of COS and drought stress caused damage to the plant’s antioxidant enzyme defence, particularly APX and GR, and reduced the amount of phenols and flavonoids. This resulted in increased ROS production and enhanced artemisinin content by 34.40% in DS plants treated with 200 mg•L-1 COS, compared to control plants. Conclusion: These findings underscore the critical role of ROS in artemisinin biosynthesis and suggest that COS treatment may boost artemisinin yield in crop production, even under drought conditions., AG-G was recipient of a predoctoral contract from the Agencia Canaria de Investigación, Innovación y Sociedad de la Información (ACIISI) and European Social Found (ESF) (TESIS2019010072). The research was partially funded by INTERREG-MAC Project APOGEO (MAC2/1.1b/226) with FEDER funds and FCT-Foundation for Science and Technology through projects UIDB/04046/2020 and UIDP/04046/2020 of the Research Unit BioISI-Biosystems and Integrative Sciences Institute (Facultade de Ciências, Universidade de Lisboa).

BACKGROUND Botrytis cinerea, the causal agent of gray mold has a great economic impact on several important crops. This necrotrophic fungus causes disease symptoms during vegetative growth and also into postharvest stages. The current method to combat this disease is fungicide application, with high economic costs and environmentally unsustainable impacts. Moreover, there is an increasing general public health concern about these strategies of crop protection. We studied the protection of tomato plants against B. cinerea by previous root treatment with menadione sodium bisulfite (MSB), a known plant defense activator. RESULTS Root treatment 48 h before inoculation with MSB 0.6 mmol L−1 reduced leaf lesion diameter by 30% and notably cell deaths, compared to control plants 72 h after inoculation. We studied the expression level of several pathogenesis-related (PR) genes from different defense transduction pathways, and found that MSB primes higher PR1 expression against B. cinerea. However, this stronger induced resistance was impaired in transgenic salicylic acid-deficient NahG line. Additionally, in the absence of pathogen challenge, MSB increased tomato plant growth by 28% after 10 days. Our data provide evidence that MSB protects tomato plants against B. cinerea by priming defense responses through the salicylic acid (SA)-dependent signaling pathway and reducing oxidative stress. CONCLUSION This work confirms the efficacy of MSB as plant defense activator against B. cinerea and presents a novel alternative to combat gray mold in important crops., This work was financed by Project ProID202010082 (Programa de Subvenciones a la Realización I + D ‘Mª Carmen Betancourt y Molina’ from ACIISI-Gobierno de Canarias with European FEDER funds). FG-M and AG-G were recipients of a predoctoral contract from the Agencia Canaria de Investigación, Innovación y Sociedad de la Información (ACIISI) and European Social Found (ESF). The article was edited by Guido Jones, currently funded by the Cabildo de Tenerife, under the TFinnova Program supported by MEDI and FDCAN funds. The authors also thank Carmen González-Bosch (IATA-CSIC, Valencia, Spain) and G. Howe (Michigan State University) for providing tomato seeds of NahG and jai1-1 respectively.

Climate change has increased the severity of drought episodes by further reducing precipitation in vulnerable zones. Drought induces a substantial decrease in agricultural water, reducing crop yields. Consequently, addressing water consumption can increase farmers’ profits. This work describes lab-to-field research in Zea mays, using two biostimulants: glycine betaine (GB) and Lpyroglutamic acid (PG). The biostimulant optimal dosages were selected using a hydroponic system with 20% polyethylene glycol and nursery experiments under water-deficit irrigation. The established dosages were evaluated in field trials in which irrigation was reduced by 20%. Laboratory biostimulant optimisation showed in stressed treated seedlings (GB 0.1 mM; PG 1 mM) an increased dry weight, relative growth rate and water use efficiency, reducing seedling growth loss between 65 and 85%, respectively. Field trials using a GB-optimised dosage showed an increase in plants’ growth, grain yield and flour Ca content. In addition, grain flour carbohydrate content and protein remained similar to control well-watered plants. Finally, the economic aspects of biostimulant treatments, water consumption, water sources (ground vs. desalinated) and grain biomass were addressed. Overall, GB treatment demonstrated to be a valuable tool to reduce water consumption and improve farmers’ earnings., This work was financed by the project AHIDAGRO (MAC2/1.1b/279), Cooperation Programme INTERREG-MAC 2014–2020, with European Funds for Regional Development—FEDER. F.J.G.M. and A.G.G., PhD students at the University of La Laguna, were supported by research fellowship contracts from the Gobierno de Canarias. A.E.H is grateful for support from the project “Plants as a tool for sustainable global development” (CZ.02.1.01/0.0/0.0/16_019/0000827) and Erasmus + HE—2015 for her mobility grant. The authors thank Natalia Usenco for her technical support during field sample processing. The manuscript was revised by G. Jones, funded by Cabildo de Tenerife under the TFinnova Programme and supported by MEDI and FDCAN.

Among its other effects, climate change is driving humanity into water scarcity, especially in highly populated areas such as the Mediterranean. One of the best options to solve this problem is seawater desalination, but it has its environmental, social and economic impacts. The brine reject effluent from the process can be used as a rich mineral source for hydroponic culture. Indeed, stability in its composition was shown here during a one-year study. A compilation of analyses from desalination facilities located worldwide also demonstrates how reutilisation of this liquid waste can provide an opportunity to build a circular economy based on brine management. Potential profitable crops and an economic study of its implementation are discussed. Correct brine management channelled into an agricultural context can be an excellent way to improve the public and ecological reputation of desalination. It can also yield extra income beyond the fresh water yield from the proposed system., F.J.G.-M. and A.G.G., PhD students at the University of La Laguna, were supported by research fellowship contracts from the Gobierno de Canarias. The manuscript was revised by G. Jones, funded by Cabildo de Tenerife under the TFinnova Programme, supported by MEDI and FDCAN. We also thank TAGUA S.L. and the Mancomunidad de los Canales del Taibilla, (especially Luis González and Ruben Navarro Barrio respectively) for providing reject brine from their seawater desalination facilities.