Browsing by Author "Magro, Ana"
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- Antifungal Activity of Benzoquinones Produced by Tribolium castaneum in Maize-Associated FungiPublication . Duarte, Sónia; Magro, Ana; Tomás, Joanna; Hilário, Carolina; Ferreira, Ricardo Boavida; Carvalho, Maria OtiliaTribolium castaneum (Herbst) adults produce 1,4-benzoquinone (BQ), methyl-1,4-benzoquinone (MBQ), and ethyl-1,4-benzoquinone (EBQ). These components are chemical defenses used as repellents and irritants, and BQ has a negative impact on the growth of some fungal species. In this work, the inhibitory and/or lethal effects of these benzoquinones on the development of six fungi identified inmaize, namely Aspergillus flavus, A. fumigatus, A. niger, Fusarium sp., Penicillium sp., and Trichoderma sp., were evaluated. Ten-day-long disk diffusion trials were performed using benzoquinones. The experiments simulated the activity of BQ (B1) or “EBQ +MBQ” (B2) released by 40-day-old insect adults (n = 200), considering a total average release of 45 g per adult. Inhibition halos imposed by benzoquinones on fungal growth showed a significant effect when compared with the controls (water and solvent). Mycelial growth was decreased for all fungi, with the level of response depending on the fungal species. B1 and B2 displayed an inhibitory effect against all fungi, but Trichoderma sp. and A. niger showed rapid recoveries. B2 showed a lethal effect on Penicillium sp. The inhibitory and lethal activities of benzoquinones released by T. castaneum adults may contribute to regulate fungal growth, and understanding their interaction is important to develop innovative control strategies
- Novel approach for a controlled delivery of essential Oils during long-term maize storage: clove bud and pennyroyal oils efficacy to control sitophilus zeamais, reducing grain damage and post-harvest lossesPublication . Sousa, Pedro A. S.; Neto, Joana; Barbosa, Joana V.; Peres, Joana; Magro, Ana; Barros, Graça; Sousa, José M.; Magalhães, Fernão D.; Mexia, António; Aguiar, Ana A. R. M.; Bastos, Margarida M. S. M.Maize grains represent a significant contribution for assuring food safety all over the globe. Sitophilus zeamais (Motschulsky) (Coleoptera: Curculionidae), also known as the maize weevil, is one of the most destructive pests in stored maize, causing qualitative and quantitative losses. To control S. zeamais populations in maize storage sites, synthetical chemical insecticides are applied. However, these are often used wastefully, have environmental implications, and can induce the development of resistant populations. In this work, the insecticidal and grain protecting efficacy of an innovative macro-capsule delivery device, loaded with essential oils from Clove bud and Pennyroyal, as well as their combined solutions, was tested against naturally S. zeamais-infested maize grains. The blend of both compounds incorporated in a controlled release device reduced losses by more than 45% over a long storage period of twenty weeks, diminishing the survivability of maize weevils by over 90%. The usage of the blend at a concentration of 370 L L1 air with an antioxidant showed the best results, however, by halving the concentration 185 L L1 air , a significant control of S. zeamais populations was still achieved.
- Paddy rice stored under hermetic conditions: the effect of relative humidity, temperature and storage time in suppressing Sitophilus zeamais and impact on rice qualityPublication . Carvalho, Maria Otilia; Fradinho, Patrícia; Martins, M.João; Magro, Ana; Raymundo, Anabela; Sousa, IsabelThe aim of this study was to analyse the effect of relative humidity in suppressing Sitophilus zeamais, in paddy rice stored under hermetic conditions, during four and seven months, at different average temperatures, as well as the impact on rice quality. Hermetic bags, GrainPro® SuperGrainbag® Farm™, were used to store two rice varieties under three different relative humidities: 67%, 75% and 85% RH, and average temperatures of 14 C, 17 C and 24 C, both monitored by Hobo® Data loggers, with the probe placed inside the bags. CheckpointII Portable O2 and CO2 Gas Analyzer was used to assess gas contents on the top and bottom of each bag. At the end of the trials, paddy samples were collected to estimate water activity (aw). The rheology behaviour of rice pastes prepared with race flour obtained from the different treatments was also evaluated, using a controlled stress rheometer. The results showed that the response of the stored-product insects changes with environmental conditions, O2 and CO2 contents. Other parameters were considered; aw increased with relative humidity and temperature, but decreased with storage time. The relative humidity played an important role, together with the increase of temperature, in suppressing insect populations. A modified atmosphere was naturally produced inside the hermetic bag, under 85% RH, with low O2 and high CO2 contents, at different average temperatures, 14 C and 17 C. These results demonstrated that S. zeamais can survive, but has no progeny. Under the same conditions, but at the higher average temperature of 24 C, S. zeamais attained 100% mortality before producing progeny. The increase on respiration rate, registered by CO2 increase and O2 decrease, for higher RH values, reduced the viscoelastic functions and changed the starch gelatinization point of Indica and Japonica rice. The results obtained showed that storing paddy hermetically, at low relative humidity, did not change atmospheric content and maintained the viscoelastic functions of the rice pastes
- Paddy rice stored under hermetic conditions: The effect of relative humidity, temperature and storage time in suppressing Sitophilus zeamais and impact on rice qualityPublication . Carvalho, Maria Otilia; Fradinho, Patrícia; Martins, M.João; Magro, Ana; Raymundo, Anabela; Sousa, IsabelThe aim of this study was to analyse the effect of relative humidity in suppressing Sitophilus zeamais, in paddy rice stored under hermetic conditions, during four and seven months, at different average temperatures, as well as the impact on rice quality. Hermetic bags, GrainPro® SuperGrainbag® Farm™, were used to store two rice varieties under three different relative humidities: 67%, 75% and 85% RH, and average temperatures of 14 C, 17 C and 24 C, both monitored by Hobo® Data loggers, with the probe placed inside the bags. CheckpointII Portable O2 and CO2 Gas Analyzer was used to assess gas contents on the top and bottom of each bag. At the end of the trials, paddy samples were collected to estimate water activity (aw). The rheology behaviour of rice pastes prepared with race flour obtained from the different treatments was also evaluated, using a controlled stress rheometer. The results showed that the response of the stored-product insects changes with environmental conditions, O2 and CO2 contents. Other parameters were considered; aw increased with relative humidity and temperature, but decreased with storage time. The relative humidity played an important role, together with the increase of temperature, in suppressing insect populations. A modified atmosphere was naturally produced inside the hermetic bag, under 85% RH, with low O2 and high CO2 contents, at different average temperatures, 14 C and 17 C. These results demonstrated that S. zeamais can survive, but has no progeny. Under the same conditions, but at the higher average temperature of 24 C, S. zeamais attained 100% mortality before producing progeny. The increase on respiration rate, registered by CO2 increase and O2 decrease, for higher RH values, reduced the viscoelastic functions and changed the starch gelatinization point of Indica and Japonica rice. The results obtained showed that storing paddy hermetically, at low relative humidity, did not change atmospheric content and maintained the viscoelastic functions of the rice pastes
- Stored products insects in Portugal – New data and overviewPublication . Duarte, Sónia; Magro, Ana; Barros, Graça; Carvalho, Maria OtiliaThe introduction of stored product insect pests to new areas is facilitated by food trade among countries, and effective detection and monitoring programs are crucial for food security. The khapra beetle, Trogoderma granarium Everts is one of the most destructive insect species. In Portugal, T. granarium has been detected in 1988. However, no new data has been added to this information since that date. Floor traps with pheromones specific to T. granarium were used and placed inside ports, mills, and storage facilities, including warehouses and silos, between June and September in 2017, 2019, 2021, and 2022.Previous results from other sampling pro- grams conducted between 2002 and 2008 are also referred here to add more evidence for the presence or absence of T. granarium in Portugal. Here, various types of traps, including some generalists and others with pheromones (such as T. granarium), were used. The collected insects were identified to species, or genus.Surveys conducted identified approximately 40 insect species that are associated with stored products, in a total of 23.725 insects, and among them, the weevils belonging to the genus Sitophilus C.J.Schoenherr have been recognized as the main pests that affects stored cereals. Regarding the surveys made between 2017 and 2022 and previous surveys done in Portugal (between 2002 and 2008; n = 26.719 insects identified), no T. granarium individuals were detected in any of the entomological samples, and only a few Dermestidae specimens were found across all surveys, one of them belonging to the same genus, identified as Trogoderma inclusum LeConte. With the predicted changes in climate, there is a risk of introducing T. granarium and other destructive insect pests that could displace Sitophilus weevils as the key stored products pest in Portugal. Therefore, it is crucial to monitor and implement measures to prevent the spread of invasive pests for effective pest management and food security purposes, using proper trapping methods and accurate and rapid identification tools.
- The Interaction between Tribolium castaneum and Mycotoxigenic Aspergillus flavus in Maize FlourPublication . Duarte, Sónia; Magro, Ana; Tomás, Joanna; Hilário, Carolina; Alvito, Paula; Ferreira, Ricardo Boavida; Carvalho, Maria OtiliaTribolium castaneum is one of the most common insect pests of stored products. Its presence makes cereals more susceptible to the spread of the fungi Aspergillus flavus, which may produce mycotoxins. The aim of this work was to evaluate the influence of T. castaneum adults on the development of a mycotoxigenic A. flavus strain in maize flour as well as the influence of this fungus on the insects. Maize flour was exposed to T. castaneum, spores of A. flavus or to both. The results revealed an interaction between T. castaneum and A. flavus as the flour exposed to both organisms was totally colonized by the fungus whereas almost all the insects were killed. Aflatoxin B1 (AFB1) revealed a significantly higher concentration in the flour inoculated with both organisms (18.8 g/kg), being lower when exposed only to A. flavus, suggesting that the presence of insects may trigger fungal development and enhance mycotoxin production. The ability of these organisms to thrive under the same conditions and the chemical compounds they release makes the interaction between them a subject of great importance to maintain the safety of stored maize. This is the first work evaluating the interaction between T. castaneum and A. flavus mycotoxin production
- The use of Laurus nobilis and Mentha pulegium essential oils against Sitophilus zeamais (Coleoptera: Curculionidae) on stored maizePublication . Barros, Graça; Magro, Ana; Conceição, Carlos; Matos, Olívia; Barbosa, António; Bastos, M.M.S.M.; Mexia, AntónioLaboratory studies were carried out to evaluate the effects of some essential oils from Laurus nobilis and Mentha pulegium against Sitophilus zeamais on stored maize. The concentrated essential oils at different volumes of 0.5 μL, 1.5 μL, 2.5 μL, 5.0 μL and 10 μL, were poured on filter papers with 2 cm Ø each. For diluted oils, the fixed volume of 15 μL of different concentrations of 1:150v/v, 1:100 v/v, 1:75 v/v, 1:50 v/v and 1:10 v/v either in methanol or n-hexane were used to impregnate the filter papers. Treatments with the concentrated oils were more effective. All the concentrations used from M. pulegium provided 100% adult mortality and no progeny production were achieved. L. nobilis has revealed 100% adult mortality at 3.185 μL/cm2. Regarding the treatments with diluted oils once again the oil from M. pulegium provided 100% adult mortality at concentrations of 1:50 v/v and 1:10 v/v. L. nobilis was not effective at any of the concentrations used. There were no significant differences between the solvents used