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- Chitosan-Enclosed Menadione Sodium Bisulfite as an Environmentally Friendly Alternative to Enhance Biostimulant Properties against DroughtPublication . Jiménez-Arias, David; Bonardd, Sebastian; Morales-Sierra, Sarai; Carvalho, Miguel Â. Almeida Pinheiro de; Díaz Díaz, DavidBiostimulants are an interesting strategy to increase crop tolerance to water deficits, and there is an extensive bibliography on them. However, most of them need to be treated continuously to increase protection throughout the growth cycle. In this context, we chose menadione sodium bisulfite, whose protective effect against water deficit has been previously demonstrated but only for a short period of time. Nanoencapsulation seems to be an interesting way to improve the properties of biostimulants. Our results show that menadione sodium bisulfite (MSB) encapsulated in chitosan/tripolyphosphate nanoparticles can increase the system’s tolerance against an imposed water deficit and delay the need for retreatment by at least 1 week, accelerating plant recovery after rehydration. This highlights the positive properties of nanoencapsulation and shows how a simple encapsulation process can significantly improve the biostimulant protective properties, opening up new possibilities to be explored under field conditions to cope with water-deficit stress.
- Development of Retrotransposon-Based Molecular Markers for Characterization of Persea americana (Avocado) Cultivars and Horticultural RacesPublication . González Carracedo, Mario; Alonso, Samuel Bello; Cabrera, Rahil Salomé Brito; Jiménez-Arias, David; Pérez Pérez, José AntonioPersea americana (avocado) represents one of the most demanded food products worldwide, with an important impact in several agronomy-based economies. The avocado is one of the most salt sensitive and valuable crops. It is therefore necessary to use salt-tolerant varieties, such as the West Indian, for cultivation in locations with soil salinity problems, such as the Canary Islands. Therefore, characterization of avocado cultivars is in demand, as well as development of molecular tools able to easily identify the main avocado cultivars and horticultural races. In the present work, inter-Primer Binding Site (iPBS) and Inter-Retrotransposon Amplified Polymorphism (IRAP) techniques, which are based on retrotransposon with Long Terminal Repeats (LTR), have been implemented for the first time in P. americana, allowing the characterization of genetic variation among cultivars from the three main horticultural races and the identification of potential P. americana LTR sequences. The iPBS approach showed clear advantages over its technical implementation, and allowed a better delimitation of horticultural races, especially when focused on West Indian cultivars. However, both techniques generated reproducible genetic fingerprints that not only allowed genetic characterization of each cultivar analyzed, but also revealed potential molecular markers for the identification of avocado cultivars and horticultural races.
- Encapsulation with Natural Polymers to Improve the Properties of Biostimulants in AgriculturePublication . Jiménez-Arias, David; Morales-Sierra, Sarai; Silva, Patrícia; Carrêlo, Henrique; Gonçalves, Adriana; Ganança, José Filipe Teixeira; Nunes, Nuno; Gouveia, Carla S. S.; Alves, Sónia; Borges, João Paulo; Carvalho, Miguel Â. A. Pinheiro deEncapsulation in agriculture today is practically focused on agrochemicals such as pes ticides, herbicides, fungicides, or fertilizers to enhance the protective or nutritive aspects of the entrapped active ingredients. However, one of the most promising and environmentally friendly technologies, biostimulants, is hardly explored in this field. Encapsulation of biostimulants could indeed be an excellent means of counteracting the problems posed by their nature: they are easily biodegradable, and most of them run off through the soil, losing most of the compounds, thus becoming inaccessible to plants. In this respect, encapsulation seems to be a practical and profitable way to increase the stability and durability of biostimulants under field conditions. This review paper aims to provide researchers working on plant biostimulants with a quick overview of how to get started with encapsulation. Here we describe different techniques and offer protocols and suggestions for introduction to polymer science to improve the properties of biostimulants for future agricultural applications.
- The use of chitosan oligosaccharide to improve artemisinin yield in well-watered and drought-stressed plantsPublication . García-García, Ana L.; Matos, Ana Rita; Feijão, Eduardo; Carvalho, Ricardo Cruz de; Boto, Alicia; Silva, Jorge Marques da; Jiménez-Arias, DavidIntroduction: 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.
- Addressing the contribution of small molecule-based biostimulants to the biofortification of maize in a water restriction scenarioPublication . Hernandiz, Alba E.; Jiménez-Arias, David; Morales-Sierra, Sarai; Borges, Andres A.; De Diego, NuriaBiostimulants have become an asset for agriculture since they are a greener alternative to traditionally used plant protection products. Also, they have gained the farmers’ acceptance due to their effect on enhancing the plant’s natural defense system against abiotic stresses. Besides commercially available complex products, small molecule-based biostimulants are useful for industry and research. Among them, polyamines (PAs) are well-studied natural compounds that can elicit numerous positive responses in drought stressed plants. However, the studies are merely focused on the vegetative development of the plant. Therefore, we aimed to evaluate how drenching with putrescine (Put) and spermidine (Spd) modified the maize production and the yield quality parameters. First, a dosage optimization was performed, and then the best PA concentrations were applied by drenching the maize plants grown under well-watered (WW) conditions or water deficit (WD). Different mechanisms of action were observed for Put and Spd regarding maize production, including when both PAs similarly improved the water balance of the plants. The application of Put enhanced the quality and quantity of the yield under WW and Spd under WD. Regarding the nutritional quality of the grains, both PAs increased the carbohydrates content, whereas the contribution to the protein content changed by the interaction between compound and growth conditions. The mineral content of the grains was also greatly affected by the water condition and the PA application, with the most relevant results observed when Spd was applied, ending with flour richer in Zn, Cu, and Ca minerals that are considered important for human health. We showed that the exogenous PA application could be a highly efficient biofortification approach. Our findings open a new exciting use to be studied deep in the biostimulant research.
- Abscisic acid mimic-fluorine derivative 4 alleviates water deficit stress by regulating ABA-responsive genes, proline accumulation, CO2 assimilation, water use efficiency and better nutrient uptake in tomato plantsPublication . Jiménez-Arias, David; Morales-Sierra, Sarai; Suárez, Emma; Lozano-Juste, Jorge; Coego, Alberto; Estevez, Juan C.; Borges, Andrés A.; Rodriguez, Pedro L.Water deficit represents a serious limitation for agriculture and both genetic and chemical approaches are being used to cope with this stress and maintain plant yield. Next-generation agrochemicals that control stomatal aperture are promising for controlling water use efficiency. For example, chemical control of abscisic acid (ABA) signaling through ABA-receptor agonists is a powerful method to activate plant adaptation to water deficit. Such agonists are molecules able to bind and activate ABA receptors and, although their development has experienced significant advances in the last decade, few translational studies have been performed in crops. Here, we describe protection by the ABA mimic fluorine derivative 4 (AMF4) agonist of the vegetative growth in tomato plants subjected to water restriction. Photosynthesis in mock-treated plants is markedly impaired under water deficit conditions, whereas AMF4 treatment notably improves CO2 assimilation, the relative plant water content and growth. As expected for an antitranspirant molecule, AMF4 treatment diminishes stomatal conductance and transpiration in the first phase of the experiment; however, when photosynthesis declines in mock-treated plants as stress persists, higher photosynthetic and transpiration parameters are recorded in agonist-treated plants. Additionally, AMF4 increases proline levels over those achieved in mock treated plants in response to water deficit. Thus water deficit and AMF4 cooperate to upregulate P5CS1 through both ABA-independent and ABA dependent pathways, and therefore, higher proline levels are produced Finally, analysis of macronutrients reveals higher levels of Ca, K and Mg in AMF4-compared to mock-treated plants subjected to water deficit. Overall, these physiological analyses reveal a protective effect of AMF4 over photosynthesis under water deficit and enhanced water use efficiency after agonist treatment. In summary, AMF4 treatment is a promising approach for farmers to protect the vegetative growth of tomatoes under water deficit stress.