Biology subjects

Garriz, A.

Publications and source records attributed to Garriz, A..

5 recordsLinked to original sources

bioRxiv2026

Biocontrol potential of endophytic bacteria against a collection of Leptosphaeria maculans isolates causing blackleg in oilseed rape

BACKGROUNDBlackleg, caused by Leptosphaeria maculans, is a major disease limiting oilseed rape production worldwide, and its management increasingly requires sustainable alternatives to chemical fungicides. In this study, we evaluated the antagonistic activity and plant growth-promoting potential of three endophytic bacteria, Bacillus velezensis Bro5, Bacillus subtilis Bro11, and Pantoea agglomerans Bru13, against a geographically diverse collection of 139 L. maculans isolates from five oilseed rape-producing regions of Argentina. RESULTSDual culture assays revealed strong inhibitory activity by Bro5 and Bro11, with mean inhibition rates of [~]80% across isolates, while Bru13 showed variable inhibition (<75% for most isolates). Greenhouse and growth chamber assays confirmed the protective potential of these strains. At the cotyledon stage, Bro11 and Bro5 reduced lesion size by 47% and 28%, respectively, while their combination achieved a 51% reduction. In greenhouse trials, combined application of Bro5 and Bro11 reduced stem base necrosis by 45% and increased the proportion of plants with [≤]50% damage to 98%, compared to only 70% in controls. Key disease metrics, including disease index, incidence, and severity, decreased by 60%, 23%, and 26%, respectively. Beyond pathogen suppression, inoculation with the Bro5-Bro11 consortium enhanced plant growth, increasing shoot biomass by 89% at early stages, and improving stem dry weight and diameter by 10% and 35%, respectively, at maturity. CONCLUSIONThese findings highlight the robustness of Bacillus endophytes as biocontrol agents, their capacity to suppress diverse pathogen isolates, and their dual role in plant growth promotion, supporting their potential integration into sustainable blackleg management programs.

microbiology↗

bioRxiv2026

Sensitivity of Argentinean isolates of Leptosphaeria maculans to Azoxystrobin, Boscalid and Prothioconazole

Blackleg, caused by Leptosphaeria maculans, is a major disease affecting oilseed rape (Brassica napus) worldwide. The use of fungicides is an essential tool for disease management; however, limited information is available regarding L. maculans sensitivity to fungicides in Argentina. In this study, the sensitivity of L. maculans isolates collected from five oilseed rape-growing regions in Argentina was evaluated against three fungicides with different modes of action: prothioconazole (DMI), azoxystrobin (QoI), and boscalid (SDHI). The effective concentration required to inhibit mycelial growth by 50% (EC50) was determined using in vitro assays. Mean EC50 values for prothioconazole, azoxystrobin, and boscalid were 0.1545 {micro}g mL-1, 0.0349 {micro}g mL-1, and 0.1557 {micro}g mL-1, respectively. A wider variability in sensitivity was observed for azoxystrobin and boscalid compared to prothioconazole. Additionally, discriminatory dose assays revealed significant differences in growth inhibition among isolates, with some showing reduced sensitivity. Spearman correlation analysis indicated a significant positive association between azoxystrobin and boscalid sensitivity at both low and high doses, suggesting potential cross-resistance. However, no significant correlations were found between prothioconazole and the other fungicides. Furthermore, isolates with reduced sensitivity (RSI < 1) did not exhibit a consistent cross-resistance pattern between QoI and SDHI fungicides, indicating that the observed correlations may be influenced by the overall distribution of sensitive isolates rather than a shared resistance mechanism. These findings provide the first insights into L. maculans fungicide sensitivity in Argentina, highlighting the need for continued monitoring to prevent resistance development and ensure effective blackleg management.

microbiology↗

bioRxiv2024

Unveiling the Virulence Mechanism of Leptosphaeria maculans in the Brassica napus Interaction: The Key Role of Sirodesmin PL in Cell Death Induction

Leptosphaeria maculans is the causal agent of blackleg disease in Brassica napus, leading to substantial yield losses. Sirodesmin PL, the principal toxin produced by L. maculans, has been implicated in the infective process in plants. However, the precise molecular and physiological mechanisms governing its effects remain elusive. This study investigates the changes induced by Sirodesmin PL at the transcriptomic, physiological, and morphological levels in B. napus cotyledons. Sirodesmin PL treatment upregulates genes associated with plant defense processes, including response to chitin, sulfur compound biosynthesis, toxin metabolism, oxidative stress response, and jasmonic acid/ethylene synthesis and signaling. Validation of these transcriptomic changes is evidenced by several typical defense response processes, such as the accumulation of reactive oxygen species (ROS) and callose deposition. Concomitantly, oxidized Sirodesmin PL induces concentration- and exposure duration-dependent cell death. This cellular death is likely attributed to diminished activity of photosystem II and a reduction in the number of chloroplasts per cell. In agreement, a down-regulation of genes associated with the photosynthesis process is observed following Sirodesmin PL treatment. Thus, it is plausible that L. maculans exploits Sirodesmin PL as a virulence factor to instigate cell death in B. napus during its necrotrophic stage, favoring the infective process. HighlightSirodesmin PL, the principal toxin produced by Leptosphaeria maculans, induces cell death and defense mechanisms in Brassica napus, disrupting photosynthesis and facilitating the infective process

plant biology↗

bioRxiv2020

Modulation of polyamine metabolism in Arabidopsis thaliana by salicylic acid

Polyamines (PAs) play important roles in plant defense against pathogens, but the regulation of PA metabolism by hormone-mediated defense signaling pathways has not been studied in depth. In this study, the modulation of PA metabolism in Arabidopsis by salicylic acid (SA) was analyzed, by combining the exogenous application of this hormone with the use of PA biosynthesis and SA synthesis/signaling mutants. SA induced notable modifications of polyamine metabolism, mainly consisting in putrescine accumulation both in whole-plant extracts and apoplastic fluids. Put was accumulated at the expense of increased biosynthesis by arginine decarboxylase 2 and decreased oxidation by copper amine oxidase. Enhancement of Put levels by SA was independent of the regulatory protein Non-Expressor of Pathogenesis Related 1 (NPR1) and the signaling kinases MKK4 and MPK3, but depended on MPK6. On its part, plant infection by Pseudomonas syringae pv. tomato DC3000 elicited Put accumulation in a SA-dependent way. The present study demonstrates a clear connection between SA signaling and plant PA metabolism in Arabidopsis and contributes to understand the mechanisms by which SA modulates PA levels during plant-pathogen interactions. HighlightSalicylic acid modulates polyamine biosynthesis and catabolism in Arabidopsis. Regulatory effects of salicylic acid are independent of the master regulator NPR1 and are mediated by the MPK6 kinase.

plant biology↗

bioRxiv2019

The fungal endophyte Fusarium solani provokes differential effects on the energy balance of two Lotus species

Background and aimsThe interactions established between plants and endophytic fungi span a continuum from beneficial to pathogenic associations. The aim of this work was to explore the mechanisms underlying the potentially beneficial effects provoked by a fungal strain in legume species of the genus Lotus.\n\nMethodsThe ability to solubilise phosphorous was evaluated in nine fungal strains isolated from roots of L. tenuis. A selected strain was further assessed for its ability to colonize plant roots in different Lotus species. The effects of the two interactions were assessed by analysis of the photosynthesis, sugar amount, and macronutrient status of leaves and roots.\n\nResultsA fungal isolate identified as Fusarium solani shows the highest phosphate-solubilisation activity and grows endophytically in roots of L. japonicus and L. tenuis. Fungal invasion enhances plant growth in L. japonicus but provokes a contrasting effect in L. tenuis. Photosynthesis, sugars and K content showed a differential effect in both plant species.\n\nConclusionsOur results indicate neither of the plant species evaluated in this work were significantly stressed by F. solani. Thus, the differential responses observed are due to distinct mechanisms involving photosynthesis, potassium homeostasis, and carbohydrate metabolism that are employed by plants to maintain fitness during the endophytic interaction.

microbiology↗