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The production of extra virgin olive oil generates significant amounts of olive mill waste, whose disposal leads to severe environmental impacts, especially due to the high content of phenolic compounds. In this study, a pomace phenolic extract composed of hydroxytyrosol, tyrosol, verbascoside, and oleuropein was obtained from the liquid fraction of two-phase olive pomace and explored for its antimicrobial properties and potential as plant immunostimulants. The olive pomace extract exhibited a broad range of antimicrobial activity against important phytopathogens, including the bacteria Xylella fastidiosa, Pseudomonas syringae, and Pectobacterium carotovorum, as well as the fungi Colletotrichum graminicola, Fusarium graminearum, and Botrytis cinerea. The extract induced key features of plant innate immunity in Arabidopsis seedlings, including hydrogen peroxide production, phosphorylation of mitogen-activated protein kinase MAPK6, and upregulation of defence genes, such as CYP81F2, FRK1, and WRKY53, suggesting the activation of early signalling cascades leading to the production of indole glucosinolates and salicylic acid. The immune activation pathways induced by the phenolic extract did not always match those triggered by well-known oligogalacturonide elicitors. Notably, pretreatment of adult Arabidopsis and tomato plants with the phenolic compounds-enriched extract primed responses and enhanced their resistance against B. cinerea and P. syringae. Our findings demonstrate the potential to upcycle two-phase olive pomace into plant protectants, offering a promising alternative to reduce reliance on chemically synthesized pesticides in integrated pest management programs.

Grafting is a horticultural technique that involves a healing process that requires grafted plants to develop physiological responses to overcome oxidative stress. In this study, oxidative damage, total antioxidant capacity and antioxidant enzymatic activities were analysed in functional and non-functional tomato autografts for eight days after grafting, considering scion and rootstock tissues separately. The results showed that oxidative damage, measured as lipid peroxidation, was controlled, especially in functional grafts. Scion tissues showed significant increases in total antioxidant capacity and activities of key antioxidant enzymes, including superoxide dismutase and catalase. Non-functional grafts showed elevated levels of class III peroxidase, potentially related to defensive suberisation and lignification. Principal component analysis revealed that antioxidant activities correlated dynamically with grafting stages, highlighting their critical role in stress mitigation. These results suggest that an efficient and asymmetric antioxidant response is essential for successful graft healing in tomato plants. Furthermore, different patterns in non-functional grafts underline the importance of redox balance in determining graft success.

Cell walls play essential roles in cell recognition, tissue adhesion, and wound response. In particular, pectins as cell-adhesive agents are expected to play a key role in the early stages of grafting. To test this premise, this study focused on examining the dynamics of the accumulation and degree of methyl-esterification of pectic polysaccharides at the graft junctions using tomato autografts as an experimental model. Monosaccharide analysis showed a marked increase in homogalacturonan from 25% to 32 or 34% at the junction zones early after grafting. In addition, a decrease in the degree of homogalacturonan methyl-esterification up to 38% in the scion and 64% in the rootstock was observed in the first few days after grafting, accompanied by an increase in pectin methyl-esterase activity of up to 20–30% in the tissues surrounding the graft junction. These results shed light on the role of homogalacturonan in grafting and reinforce the key function of pectin as one of the most relevant cell wall components during the grafting process.

Grafting is a technique applied to a considerable number of crops, with tomato standing out. However, this technique is limited by the obtaining of unfunctional grafts, which decrease the success rate and therefore the benefits achieved. The aim of this work was to analyze the failure in intraspecific grafting of tomato plants, focusing on tissue development, cell wall defense reactions, and the distribution of starch and soluble sugars at the graft junction. The success rate in autografts was higher than that of homografts and heterografts. Unfunctional homografts and heterografts showed similar responses: absence of vascular reconnections and lack of adhesion between scion and rootstock, even though callus cell clusters and differentiation of new vasculature were produced. The scions of unfunctional grafts accumulated more starch and soluble sugars than the rootstocks, showing a strong asymmetry in the response. In addition, three types of deposits were observed in the cell walls of unfunctional grafts: lignin, suberin, and callose, with the combined accumulation of more than one of them being frequent, particularly lignin and suberin. These deposits apparently prevent adhesion and seem to be a major cause of graft failure.

Despite the importance of grafting in horticultural crops such as tomato (Solanum lycopersicum L.), the structural changes that occur during the graft establishment are little understood. Using histological techniques, the present work examines the time course of changes on the anatomical structure of the graft junction in functional tomato homografts and compares it to that of heterografts and non-functional grafts. No apparent differences were detected between homo- and heterografts, showing similar tissue development. At 10 days after grafting, the cell walls of the scion and rootstock in the area of the graft junction were thicker than usual. Undifferentiated cells and new vascular tissue emerged from the pre-existing vasculature. Adventitious roots appeared mainly on the scion, arising from the pre-existing vasculature. At 20 days, more pronounced vascular tissue was visible, along with large areas showing vascular connection. At 210 days, vestiges of the changes undergone in graft development were still visible. Generally, non-functional grafts presented layers of necrotic remains and deposition of cell wall material in the cut edges, impeding the suitable scion-rootstock connection. Our results show that accurate changes in pre-existing vasculature and the cell walls of the adhesion line are crucial to the development of functional grafts.

El objetivo de este estudio fue determinar la seroprevalencia de anticuerpos contra SARS-CoV-2. Para ello, entre el 21 de noviembre y el 12 de diciembre del año 2020, se desarrolló un estudio transversal en 1182 muestras de residentes de un municipio bonaerense en la Provincia de Buenos Aires, Argentina. Se midió IgG por ELISA en muestras obtenidas vía digitopunción. La prevalencia general fue del 12,2 % (n = 144; IC95 %: 10,3 – 14,0) con un cociente 1:3,8 entre la incidencia acumulada y la observación en nuestro estudio; en mujeres fue del 13,0 % (IC95 %: 10,2 – 15,7) y en hombres, del 10,5 % (IC95 %: 7,6 – 13,3) (p = 0.21). Las prevalencias en grupos etarios fueron las siguientes: 18 a 30 años, del 17,8 % (IC95 %: 12,0 – 23,6); 31 a 60 años, del 12,2 % (IC95 %: 9,3 – 15,1) y 61 años o más, del 9.9 % (IC95 %: 6.9 - 13.9) (p = 0.02). Las prevalencias según los terciles socioeconómicos (por Necesidades Básicas Insatisfechas) fueron para el Tercil I (mejor tercil): 7,7 % (IC95 %: 4,7 – 10,7); el Tercil II: 12.5 % (IC95 %: 8,7 – 16,4); y el Tercil III: 15,2 % (IC95 %: 11,6 – 18,8) (p = 0.002). También hubo diferencias entre las localidades de dicho municipio y entre variables clínicas autorrefenciadas. Se detectaron 12 muestras positivas para IgM: el 1 % del total y el 8,3 % respecto de los casos IgG-positivos. Los estudios de seroprevalencia resultan útiles y podrían contribuir a modelizaciones matemáticas más ajustadas.