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In this study, we gathered data on Fusarium head blight (FHB) severity, deoxynivalenol (DON), and wheat yields from 19 cooperative fungicide trials conducted in Southern Brazil over five growing seasons (2017-2021). We tested three QoI + DMI premixes (PYRAclostrobin + METConazole, TEBUconazole + TriFLoXystrobin, and TriFLoXystrobin + PROThioconazole), one triple premix of QoI + DMI + SDHI (TriFLoXystrobin + PROThioconazole + BIXaFen), and two single active ingredients (METC and CARBendazim [MBC]) applied three times, beginning at the flowering stage and continuing every 7-12 days. We fitted a network meta-analysis model to the log of the means of FHB index and DON content data and to the non-transformed mean yield for each treatment, including the untreated control. Disease (FHB index) reduction estimates ranged from 41.5% (TEBU + TFLX) to 62.8% (METC); the latter did not differ from PYRA + METC (56.1%). Likewise, the mean estimates of percent DON reduction were higher for METC (65.1%) and PYRA + METC (58.3%). These two treatments were followed by TEBU + TFLX (50%), which was not statistically different from CARB (48%) and TFLX + PROT (45.2%), but differed from TFLX + PROT + BIXF (39.3%). Lastly, the yield response was higher for TFLX + PROT + BIXF (643 kg/ha), which differed from all other treatments, including METC (505.9 kg/ha), PYRA + METC (477.8 kg/ha), TFLX + PROT (455.3 kg/ha), CARB (453.2 kg/ha), and TEBU + TFLX (403.4 kg/ha). The results of this meta-analysis are crucial for informing decisions during the planning of fungicide programs aimed at controlling FHB and reducing DON in wheat.

The plant surface is one of the first sites of contact with microorganisms, where structures such as the cuticle and trichomes are responsible for interfering with this initial interaction. Trichomes, while protecting plants from microorganisms, can also facilitate infection by pathogens. The density of trichomes varies among species, and the amount and type of these structures in plant organs can confer resistance or susceptibility of plants to microorganisms. The trichomes, non-glandular and glandular, act as a barrier, preventing the adherence of the infective structures of the pathogens on the plant surface. In addition, glandular trichomes also secrete exudates (products of plant metabolism), which have antimicrobial properties, negatively interfering with the development of many bacterial and fungal diseases. However, both trichomes are favorable sites for the penetration and multiplication of plant pathogens, possibly because they provide a certain level of moisture and nutrients for the development of fungi and bacteria. Contrary to the view that trichomes only provide protection against plant pathogens, by hindering their adhesion, they can also become preferential sites for infection.

Olive (O. europaea L.) is an expanding crop in the south of Brazil. Blossom blight and typical anthracnose symptoms on fruit were observed in olive trees in an orchard in Rio Grande do Sul, Brazil. Fungi were isolated from symptomatic flowers. Fungal isolates were confirmed as pathogenic after Koch’s postulates were fulfilled. Blossom blight and typical anthracnose symptoms with salmon conidial masses were observed in flowers of cultivars Arbosana and Arbequina, at 96 h after inoculation (hai), and on fruits of cultivar Arbosana, at 120 hai. The identification of the pathogens was carried out using a polyphasic analysis approach, combining morphological and molecular characters of specific genomic regions (ITS, GAPDH, ACT, HIS3, and TUB2). Morphological characters and phylogenetic analyses revealed the isolates as Colletotrichum acutatum and Colletotrichum nymphaeae. Until now, the species C. nymphaeae had not been identified as causing anthracnose in olive trees in Brazil.

Leaf spot diseases caused by fungi pose a serious threat to forage crops due to the reduced photosynthetic area, which dramatically affects yields. Aiming to expand knowledge of fungi causing leaf spot diseases in ryegrass (Lolium multiflorum) from southern Brazil, a comprehensive survey was undertaken. Seven species of plant pathogenic fungi were encountered. All species were identified by using a polyphasic approach combining morphological, ecological, and molecular sequences of seven genomic loci (actin, calmodulin, glyceraldehyde 3-phosphate dehydrogenase, histone, ITS, LSU, and partial translation elongation factor 1-α). The pathogenicity of representative strains of each species was also tested after artificial inoculations. Cercospora sp. G, Colletotrichum plurivorum, and Exserohilum rostratum represent new-host associations, Bipolaris sorokiniana, Pyrenophora nobleae, and Pyricularia oryzae are newly reported for Brazil, and Curvularia lolii is newly described. These results form the basis to identify these diseases in the field, which in the future can help agronomists and farmers to design strategies for integrated control and management in crop-livestock production systems.

Our study aimed to assess the structure and distribution of plant-parasitic nematodes in soybean [Glycine max (L.) Merr] in the south of Brazil. High taxonomical diversity was found, with records of 10 genera of plant-parasitic nematodes (PPNs), including important pests, such as Meloidogyne (mostly M. javanica with small esterase variability), Pratylenchus (mostly P. brachyurus) and Helicotylenchus spp. The Shannon-Weaver index (H′) ranged from 0 to 1.23 (mean = 0.37), whereas Pielou’s evenness (J) ranged from 0 to 1 (mean = 0.51). The amount of PPNs (0 to 22,050 per 250 cm3 soil, and 0 to 15,500 per 10 g roots), incidence and abundance for Meloidogyne (28.6%; 50 to 19,250 per 250 cm3), Pratylenchus (45.1%; 50 to 550 per 250 cm3), Helicotylenchus (91.2%; 50 to 9,150 per 250 cm3), Tylenchus (34.1%; 50 to 550 per 250 cm3), Xiphinema (33%; 50 to 250 per 250 cm3), Mesocriconema (15.4%; 50 to 2,000 per 250 cm3), Rotylenchus (8.8%; 50 to 1,900 per 250 cm3), Hemicycliophora (1.1%; 50 per 250 cm3), Discocriconemella (1.1%; 950 per 250 cm3) and Tylenchorhynchus (1.1%; 50 per 250 cm3) were related differently to the bioclimatic variables under analysis. Our findings provide an update for the status of PPNs in the south of Brazil and suggest important epidemiological issues linked to the management of these pests in the near future.

O objetivo da pesquisa foi avaliar o efeito residual do tratamento das sementes de cevada com fungicida e fertilizante silicatado no controle da mancha marrom no estágio vegetativo da planta. O delineamento experimental utilizado foi inteiramente casualizado em esquema bifatorial 4 × 3, constituído por quatro tratamento de sementes (TS): testemunha (água destilada), fungicida (triadimenol), fertilizante silicatado e a mistura fungicida + fertilizante silicatado e plantas com 30, 45 e 60 dias após a emergência (DAE). Para avaliar o efeito residual (TS), as plantas foram inoculadas com uma suspensão de esporos de Bipolaris sorokiniana. A avaliação da severidade ao longo do tempo foi utilizada para calcular a área abaixo da curva de progresso da mancha marrom (AACPMM). Aos 30 DAE, o tratamento com fungicida foi o mais eficiente com a redução de 64% na AACPMM, seguido do fertilizante silicatado com 56%. A mistura também reduziu a AACPMM, mas com eficiência inferior aos produtos isolados.

Silicon (Si) efficiently controls Podosphaera xanthii in melon by affecting epidemic components related to the infection and colonization processes. Root amendments of Si prime melon defences, but its mode of action when sprayed on the leaves is unknown. The effects of potassium silicate (PS) on the development of the pathogen were observed by scanning electron microscopy. Both forms of PS application reduced conidial germination and delayed colony development. At 120 h after inoculation (hai), differentiation of the conidiophores was inhibited only by the root treatment and at 144 hai visual differences between PS treatments accentuated. Comparison of foliar PS with compounds of contrasting pH and ionic strength (KOH, KCl and PEG) showed that only PS and PEG inhibited conidial germination ruling out these variables as inhibitory factors. Alteration of the leaf surface tension was also excluded since it was affected by all compounds. The results indicate that foliar-applied PS affects P. xanthii conidial germination of and colony development by modifying the osmotic potential of the leaf surface.

This study aimed to develop and validate a standard area diagram set (SADs) to estimate the severity of eyespot of rice caused by Drechslera gigantea. For this purpose, a SADs with seven levels of severity (0.3; 1.0; 3.0; 5.0; 10; 15; and 21%) was established. The SADs was validated by 16 raters with no experience in evaluating plant diseases. Both accuracy and precision improved when they used the SADs. The statistical parameters for the 16 raters were: bias coefficient factor - Cb (no SADs = 0.404, with SADs = 0.994); correlation coefficient - r (no SADs = 0.884, with SADs = 0.953); and Lin’s concordance correlation coefficient - ρc (no SADs = 0.356, with SADs = 0.947). In addition, estimates were more reliable: inter-rater coefficient of determination - R2 (no SADs = 0.712, with SAD = 0.873); intra-class correlation coefficient - ρ (no SADs = 0.723, with SADs = 0.924). The SADs proposed here is a useful tool for improving visual assessments of eyespot severity of rice.

The leaf anatomy, photosynthetic system parameters and accumulation of carbohydrates were determined at different times for Bipolaris oryzae pathogenesis in two rice cultivars (BRS Querencia and Inov CL), grown in an environment with 400 ppm or 700 ppm of atmospheric CO2. The results demonstrated that the plants exposed to 700 ppm underwent changes in anatomical characteristics (reduction in parenchyma thickness and size of bulliform cells), photosynthetic parameters (increased carbon assimilation rate, leaf intercellular CO2 concentration and water use efficiency, and reduction of stomatal conductance to water vapor, transpiration rate and carboxylation efficiency), and carbohydrate accumulation (increased concentration of soluble sugars and starch), when compared to plants at 400 ppm. Therefore, the changes in morphological traits of the leaf and the accumulation of carbohydrates, which were stimulated in the rice plants by increased CO2 concentration (700 ppm), were associated with less severe brown spot, caused by B. oryzae.

The objective of this work was to assess the effect of acibenzolar-s-methyl, potassium phosphite, potassium silicate, and trifloxystrobin + prothioconazole products on curative control of powdery mildew (Microsphaera diffusa) in soybean. The experimental design was completely randomized, in a single factor scheme, containing five treatments with four replications. The products were applied on leaves at the V4 phenological stage, with disease severity of 5%. At 7, 14, and 21 days after the application of the products (DAA), the incidence and severity of the disease were assessed. The trifloxystrobin + prothioconazole reduced by 30% the disease incidence and 80% disease severity compared to the control. The inhibitory effect of the products on conidia production in vivo and its germination in vitro were also assessed. Trifloxystrobin + prothioconazole was more effective in the reduction of both conidia production and germination. Acibenzolar-s-methyl, potassium phosphite, and potassium silicate reduced conidia germination, but neither affected the disease severity nor the conidia production. Based on this, it can be concluded that the fungicide trifloxystrobin + prothioconazole reduced the production of conidia and inhibited its germination, showing curative and protective effect against soybean powdery mildew and that the resistance inducers tested interfered with pathogen germination, but without significant effect on the disease when applied after the onset of symptoms.

O arroz é um dos cereais mais cultivados no Brasil. O incremento de CO2 atmosférico é uma das principais variáveis ambientais que podem afetar a produtividade das plantas cultivadas. Assim, o objetivo neste estudo foi avaliar os efeitos da elevação da concentração do CO2 atmosférico sobre características morfofisiológicas e rendimento de grãos em dois genótipos de arroz no Sul do Brasil. Para tal, plantas de arroz das cultivares BRS Querência e Inov CL foram cultivadas sob duas concentrações de CO2 (400 ou 700 ppm). As variáveis avaliadas foram trocas gasosas, alterações morfológicas e componentes de rendimento de grãos. Plantas cultivadas a 700 ppm de CO2 apresentaram aumento na taxa fotossintética e na concentração interna de CO2 e redução na condutância estomática de vapores de água e na taxa transpiratória. Nestas plantas ocorreu incremento na estatura, comprimento de raiz e massa seca da parte aérea e de raiz, em estágio vegetativo. No estágio reprodutivo, plantas cultivadas a 700 ppm de CO2 apresentaram incremento na estatura e na massa seca de raiz. Em relação ao rendimento, ocorreu incremento no número de grãos por panícula, no peso de mil grãos, no peso por panícula e redução de grãos chochos. Assim, concluímos que o incremento na concentração de CO2 atmosférica influência no desempenho agronômico do arroz cultivado no Brasil através de alterações fisiológicas, ganho de biomassa e no incremento do rendimento de grãos.

RESUMO A mancha parda (Bipolaris oryzae) é uma das mais importantes doenças foliares do arroz. Nesse estudo, alguns componentes de resistência e algumas variáveis bioquímicas amplamente conhecidas como mecanismos de defesa de plantas contra patógenos foram avaliadas em genótipos de arroz classificados, segundo SOSBAI, como moderadamente suscetível, moderadamente resistente e resistente, buscando entender epidemiológica e bioquimicamente como ocorre a variação na resistência dos diferentes genótipos. Sete cultivares de arroz foram inoculadas com 1 × 104 conídios mL-1 de B. oryzae nas quais foram avaliados os seguintes componentes de resistência: eficiência relativa de infecção (ERI); número final de lesão (NFL); comprimento final de lesão (CFL); taxa de expansão de lesão (r) e a severidade final (SF). Além disso, também foram avaliadas variáveis bioquímicas, como atividade das enzimas superóxido dismutase (SOD), catalase (CAT), peroxidase (POX), quitinase (QUI) e fenilalanina amônia-liase (FAL). Os resultados demonstram diferenças significativas entre as cultivares para os componentes de resistência, bem como nas atividades enzimáticas. Todos os genótipos testados foram suscetíveis a B. oryzae, variando quanto ao nível de resistência parcial a mancha parda. As variáveis de r e CFL apresentaram maior correlação com a SF indicando serem as variáveis que mais influenciam a intensidade final da doença em cada genótipo. Os genótipos com maior resistência parcial a mancha parda apresentaram alterações caracterizadas como antecipação, potencialização e prorrogação da atividade das enzimas QUI, FAL, CAT e POX.

Contamination of foods by mycotoxins is a reality. However, emerging technologies such as ozonization can be used to reduce the levels of these contaminants. Thus, the aim of this study was to evaluate the effects of using ozone at different period and application times during the soaking step of parboiling process. Samples were analyzed for qualitative and quantitative analysis of mycotoxins, swelling power and solubility, head rice yield, protein solubility, cooking time, texturometric profile, colorimetric profile and defective grains. The results showed tha parboiled rice grains treated with ozone present significant reduction of mycotoxins contamination, regardless of the time and period of application and the mycotoxin evaluated. Regardig to technological properties, the samples treated with ozone in the final 3 h and for 5 h of soaking presented higher head rice yield, luminosity and hardness, with decreases in cooking time, percentage of defective grains and soluble protein.

Tan spot, caused by Pyrenophora tritici-repentis, and fusarium head blight (FHB), caused by the Fusarium graminearum species complex, are among the main wheat diseases worldwide. This 3-year field study evaluated the effect of soil incorporation of calcium silicate, a source of silicon (Si), to manage tan spot and FHB and improve grain yield and quality. The effect of Si was compared on two cultivars contrasting in disease resistance and associated with one or two fungicide sprays. Calcium silicate fertilization increased the Si concentration in the soil and wheat leaf and spike tissues. The increase of Si concentration in wheat tissues was associated with reduction in the severity of both tan spot and FHB, consequently increased the quality and grain yield of wheat. The reduction of disease severity conferred by Si was greater for tan spot than FHB. The greatest control of tan spot and FHB was obtained with the moderately resistant cultivar grown in soil amended with calcium silicate (+Si) and treated with two fungicide sprayings. On the other hand, the highest grain yield, under high disease pressure, was obtained in +Si plants, regardless of the cultivar, treated with two fungicide sprays. The results of this study show for the first time that the incorporation of Si in the soil complemented the effect of genetic resistance and fungicide treatments in controlling both tan spot and FHB. Furthermore, results indicate that calcium silicate fertilization is useful as part of integrated management of these wheat diseases.

Silicon (Si) is a benefic element for higher plants such as wheat (Triticum aestivum) in which it is accumulated in the shoot tissues. In this crop, leaf diseases and spike diseases are the cause of yield losses, and therefore several studies had been conducted under field and greenhouse conditions to demonstrate that plants supplied with Si reduced most of the diseases damage due to the amelioration of the plant defenses. However, the benefits of Si depend on its accumulation in the plant’s tissue, which is influenced by the availability of the element in the soil as well as the up-take ability of the wheat cultivar. In this chapter we present the current knowledge about the mechanisms of Si absorption and its accumulation in different tissues of the wheat plant, the most studied options for silicate fertilization, and the benefits of Si on grain yield. We also present some insight of the effect of Si-supply in wheat on the reduction of main leaf and ear diseases, bringing evidence and explanation of the defense mechanisms involved. In addition, we provide an overview of the Si effect on the physiology (gas exchange, chlorophyll a fluorescence and carbohydrate metabolism) of the wheat plant. Finally, questions have been raised about the Si uses as fertilizer that still needs to be answered. We recognized that some studies have enhanced our understanding of Si providing evidence of the Si use as disease management strategy, but further research is needed to make the Si uses a simple task for wheat growers under field condition.

Fusarium head blight (FHB), caused mainly by Fusarium graminearum, is best controlled with demethylation inhibitor (DMI) fungicides applied during flowering. However, the use of premixes of DMI and quinone outside inhibitor (QoI) fungicides to control FHB has increased in Brazil, but the individual results are inconsistent. Data on FHB severity and wheat yields measured in field experiments conducted in Brazil were gathered from both peer- and non-peer-reviewed sources published from 2000 to 2018. After applying selection criteria, 35 bibliographic sources, contributing 73 (50% from cooperative trials) trials, were identified. At least one of four DMI+QoI premixes and one tebuconazole (TEB) treatment, applied mostly twice (full-flowering and 10 days) tested in at least 14 trials and three year each, were present in a selected trial. Estimates of percent control (and respective 95%CI) by a network model ranged from 44.1% (pyraclostrobin + metconazole applied once; 32.4 - 53.7) to 64.3% (pyraclostrobin + metconazole; 58.4 - 69.3); the latter not differing from TEB (59.9%, 53.6 - 65.3). Yield response was statistically similar for pyraclostrobin + metconazole (532.1 kg/ha, 441 - 623) and trifloxystrobin + prothioconazole (494.9 kg/ha, 385 - 551), and both differed statistically from a group composed of TEB (448.2 kg/ha, 342 - 554), trifloxystrobin + TEB (468.2 kg/ha, 385 - 551), azoxystrobin + TEB (462.4 kg/ha, 366 - 558) and pyraclostrobin + metconazole applied once (413.7 kg/ha, 308 - 518). The two categories of FHB index (7% cut off) and yield (3,000 kg/ha), both in the non-treated check, did not explain the heterogeneity in the estimates. The probability of not-offsetting control costs was generally lower than 0.45 for scenarios considering two sequential sprays of the low-cost TEB or one spray of pyraclostrobin + metconazole as management choices. The envisioned enhanced economic return, solely based on yield response, from using two sprays of DMI+QoI premixes to control FHB should be seen with caution given the marginal levels of profitability.

O objetivo da pesquisa foi avaliar o efeito da aplicação dos sais inorgânicos cloreto de potássio (KCl), hidróxido de potássio (KOH) e silicato de potássio (K2O3Si) sobre laranja no controle do bolor verde causado por Penicillium digitatum. O delineamento experimental utilizado foi inteiramente casualizado com cinco tratamentos e quatro repetições, cada uma composta por vinte frutos. Os frutos foram lavados, desinfestados e feridos com uma agulha (2-3 mm de profundidade), após 24 h foram tratados com os sais inorgânicos ou água destilada (controle) e 2 h após, inoculados por meio da deposição de 15 µL da suspensão de esporos de P. digitatum. Às 96, 120 e 245 horas após a inoculação (hai) foram realizadas as avaliações de incidência do bolor verde, taxa da expansão da lesão, tamanho da lesão e da área esporulante. Às 245 hai, entre os sais, o KOH e o K2O3Si foram os mais efetivos, afetando todas as variáveis avaliadas, reduzindo a incidência da doença em 80% e 36%, respectivamente, quando comparados à testemunha. Contudo, o tratamento com o KOH afetou a qualidade visual dos frutos, ocasionando enrugamento e desidratação da casca. Desse modo, conclui-se que, entre os sais inorgânicos testados, o K2O3Si (50 g.L-1) apresentou redução no bolor verde sem comprometer a qualidade visual do fruto, podendo ser incluído como uma medida complementar no manejo da doença.

Tan spot caused by Pyrenophora tritici‐repentis is a disease present in all wheat‐producing countries and silicon (Si) treatment of wheat plants has been shown to increase plant resistance to tan spot. In this study, the effect of phenylpropanoid metabolism on resistance to tan spot was evaluated and some phenolic compounds that accumulated in response to P. tritici‐repentis attack were identified. Furthermore, the effect of Si on phenylalanine ammonia‐lyase (PAL) activity and phenolic compound accumulation were determined in situ. Antifungal activity of differentially accumulated phenolic compounds was also evaluated in in vitro tests. Results showed that the increase in concentration of phenolic compounds was greatest at the onset of infection, and that some compounds showed fungitoxic effects including fungal tip swelling, granulation of germ tube and hyphae, and hyphal hyperbranching. Silicon‐induced reduction in both lesion size and tan spot disease progression were associated with activation of phenylpropanoid metabolism. PAL activity and accumulation of antifungal phenolic compounds were greater in pathogen‐inoculated plants supplied with Si. In these plants, fluorescence indicative of accumulation of phenolic compounds occurred early in epidermal cells and its intensity increased during the evaluation period, showing higher numbers of fluorescent cells around infected cells. Thus, the combined responses of cell fluorescence at sites of infection, increased PAL activity and accumulation of phenols indicate that Si strengthened wheat defence responses to infection by P. tritici‐repentis, reducing the severity of tan spot.

Wheat (Triticum aestivum L.) is affected by several diseases that reduce significantly the yield. In this study, carried out in 2012 and 2014, the mixtures of cultivars with different resistance level to disease were evaluated as a strategy to the management of leaf and ear diseases. The mixtures (treatments) were in the proportion of 100, 75, 66, 50, 34, 25 e 0% of the susceptible cultivar. Fusarium head blight (FHB) (Fusarium graminearum complex species) evaluation was performed in 400 ears per treatment. Severities of wheat leaf rust (Puccinia triticina), tan spot (Pyrenophora tritici-repentis) and powdery mildew (Blumeria graminis f. sp. tritici) were quantified on all leaf and considering only the flag one. FHB, tan spot and powdery mildew occurred in both crop seasons, while leaf rust occurred only in 2014. The reduction in the diseases intensities followed the reduction in the number of susceptible plants in the population, however, the mean severity of treatments was lower than the simple dilution of the susceptible population. The higher severity reduction, up to 41%, for leaf diseases occurred with up to 50% of the susceptible cultivar in the population. In conclusion, the cultivar mixture of two components is effective for reduction in the intensities of multiple wheat diseases, but additional measures will be necessary depending on diseases and climatic conditions prevailing during the crop season.

Tan spot caused by Pyrenophora tritici-repentis is the main foliar diseases of wheat in Brazil. The effect of silicon (Si) on the components of resistance of a susceptible (Fundacep Horizonte) and a moderately resistant (Quartzo) wheat cultivar was studied in a controlled environment. Silicon was supplied as calcium silicate in the soil 30 days before sowing. At the booting stage, a conidial suspension of the fungus was sprayed onto the flag leaves of potted plants, which were incubated under moist conditions for 48 h. Afterwards, inoculated leaves were assessed for: incubation period (IP), infection efficiency (IE), area under lesion size curve (AULSC), lesion size (LS), severity (SEV) and area under severity curve (AUSC). Foliar Si concentrations were quantified at the end of the evaluations. Si supply to plants increased leaf Si concentration in 233% for Fundacep Horizonte (from 4.8 to 16.0 g kg−1 of dry matter) and 211% for Quartzo (from 5.3 to 16.5 g kg−1 of dry matter). In the Si + treatments, IP was longer by 24 and 17 h, IE declined by 53.5 and 65.5%, LS (at 264 h after inoculation) by 4.6 mm (from 9.5 to 4.9 mm) and 5.9 mm (from 8.2 to 2.3 mm), and SEV by 53% (from 54.4 to 18.8%) and 88% (from 47.7 to 5.5%) respectively, for the Fundacep Horizonte and Quartzo cultivars. The Si x cultivar interaction was not significant for AULSC and AUSC, and these variables were reduced by 55.8 and 80.8%, respectively, in plants supplied with Si. In conclusion, Si enhanced the resistance of wheat plants to tan spot development by affecting several resistance components, regardless of the resistance level of the cultivar. However, the greatest reduction in tan spot development by Si supply was observed when using a moderately resistant cultivar.

This work aimed to verify the existence of patterns on the electrophysiological systemic responses of tomato plants inoculated with a pathogenic fungus in an environment with controlled light and temperature. Electrical signalling was measured before and after inoculation in the same plants, and data were analysed with time series techniques and approximate multi-scale entropy (ApEn). Machine learning algorithms were utilised in order to classify data before and after infection throughout the five days of experiments. The obtained results have shown that it is possible to distinguish differences in the plant's electrome activity before and after the fungus inoculation. In some cases, we have found scale invariance quantified by the power law decay in the distribution histogram. We also found a higher degree of internal organisation quantified by ApEn. The results of the classification algorithms achieved higher accuracy of infection detection at the initial stage of pathogen recognition by the plant. Besides, this study showed evidence that long-distance electrical signalling is likely involved in the plant-pathogen interaction, since signals were obtained in the stem and the inoculum applied on the plant leaves. This might be useful for the early detection of plant infections.

Flamboyant (Delonix regia) is an ornamental tree that is native to Madagascar and frequently used in gardens and parks worldwide. Powdery mildew was observed on flamboyant plants in the cities of Piracicaba and São Carlos (State of São Paulo, Brazil) during the springs of 2010 and 2011. All sampled plants (~15 plants) were affected by the disease. Affected plants had abundant, white powdery masses of conidia and mycelium on floral buds that is typical of powdery mildew, but these structures were not observed on leaves and petioles. Diseased buds were observed at all developmental stages. The fungus was identified as Erysiphe quercicola on the basis of scanning electron microscopy, light microscopy, and sequence analysis of the internal transcribed spacer (ITS) region. Conidia were produced in short chains of four to five spores on erect conidiophores. Conidiophores were unbranched, cylindrical, 50 to 80 μm long (mean 68.8 ± 10.8 μm), composed of a cylindrical foot cell 25 to 40 μm long (mean 32.2 ± 4.9 μm), and one to two shorter cells. Conidia were ellipsoid-ovoid to subcylindrical, 22 to 37 μm long (mean 30.9 ± 4.4 μm), and 10 to 18 μm wide (mean 15.1 ± 2.8 μm). Germ tubes were produced apically and ended in a lobed appressorium. Colonizing hyphae also had a well-developed lobed appressorium. Chasmothecia were not observed on buds. DNA was extracted from conidia, conidiophores, and mycelium and used to amplify the ITS (ITS1-5.8s-ITS2) region using the ITS1 and ITS4 primers (2) and its sequence (612 nt) was deposited under Accession No. JQ034229 in the GenBank. Searches with the BLASTn algorithm revealed 100% similarity with E. quercicola from oak (Accession Nos. AB292693.1, AB292691.1, and AB292690.1) (1). To fulfill Koch's postulates, 10 detached young floral buds, 0.4 to 0.8 cm in diameter, were inoculated with five to eight conidia collected on floral buds using an eyelash brush. Inoculated buds were placed on moistened filter paper in petri dishes. The negative control consisted of noninoculated young floral buds. Inoculated and noninoculated buds were incubated in a growth chamber at 25°C and a 12-h photoperiod. Powdery mildew structures were observed 6 to 8 days after inoculation. To our knowledge, E. quercicola has not been reported previously as a pathogen of flamboyant tree since there is no record in the Erysipahales database ( http://erysiphales.wsu.edu/ ). Although the economic impact of the disease is limited, its incidence might induce the abortion of floral buds and accelerate the senescence of flowers, thus reducing the aesthetic value of the trees. References: (1) S. Takamatsu et al. Mycol Res. 111:809, 2007. (2) T. J. White et al. PCR Protocols: A Guide to Methods and Applications. Academic Press, San Diego, 1990.

The plantain Plantago australis Lam. (Plantaginaceae) is a herbaceous species native to southern Brazil that is known for the analgesic, antibiotic, and anti-inflammatory properties of its leaf extracts (2). Powdery mildew was observed on wild P. australis plants in the cities of Tapejara, Jari, and Santa Maria (State of Rio Grande do Sul, Brazil) during the summer of 2011. Affected plants were more often observed in shaded areas. Signs included sparse to abundant white powdery masses of conidia and mycelium on pseudo-petioles and leaves, mostly on the adaxial surface. Severely affected plants (≥80% of foliar area affected) had small chlorotic leaves and reduced size compared to healthy ones. Mycelia were superficial and presented nipple-shaped appressoria. Conidiophores were often curved at the base, unbranched, cylindrical, 81 to 125 μm long (average 97.3 ± 14.9 μm) and composed of a cylindrical foot cell 52 to 73 μm long (average 65.4 ± 7.5 μm) and 9 to 14 μm wide (average 11.6 ± 1.5 μm) followed by one to two shorter cells 17 to 29 μm long (average 23.4 ± 3.6 μm). Conidia were produced in chains of up to eight cells, did not contain fibrosin bodies, ranged from ellipsoid-ovoid to subcylindrical, and measured 24 to 35 μm long (average 30.5 ± 3.7 μm) and 12 to 19 μm wide (average 15.8 ± 1.7 μm). Germ tubes were produced apically (reticuloidium type). Chasmothecia were not observed on sampled leaves. Genomic DNA was extracted from conidia, conidiophores, and mycelium and used to amplify the internal transcribed spacer (ITS) (ITS1-5.8s-ITS2) region using the ITS1 and ITS4 primers. The resulting sequence (558 bp) was deposited under accession number JX312220 in GenBank. Searches with the BLASTn algorithm revealed similarity of 100% with Golovinomyces orontii (Castagne) V.P. Heluta 1988 from Veronica arvensis L. (AB077652.1) (3), 99% with G. orontii from Galium spurium L. and Galium aparine L. (AB430818.1 and AB430813.1) (2) and 99% with G. sordidus (L. Junell) V.P. Heluta 1988 from P. lanceolata L. (AB077665.1) (3). Based on morphological characteristics and sequence analysis of the ITS region, the fungus was identified as belonging to Golovinomyces sp. To fulfill Koch's postulates, five cultivated plants of P. australis with four to five expanded leaves were inoculated by dusting conidia (10 to 15 conidia cm–2) on their leaves. Inoculated and non-inoculated control plants were kept in a greenhouse at 27 ± 5°C and relative humidity of 80 ± 15%. Powdery mildew symptoms identical to those of wild plants were observed 8 to 10 days after in inoculated plants. Although G. sordidus was previously reported on P. australis subsp. hirtella in Argentina and on several species of Plantago in others world regions (1), to our knowledge, Golovinomyces sp. has not been previously reported as a pathogen of P. australis in Brazil. Although the economic impact of the disease is limited, the reduction in plant size and leaves affects biomass production used in the extraction of pharmaceutical compounds. References: (1) U. Braun and R. T. A. Cook. Taxonomic Manual of the Erysiphales (Powdery Mildews), CBS Biodiversity Series 11, 2012. (2) G. C. Sousa et al. J. Ethnopharmacol. 90:135, 2004. (3) S. Takamatsu et al. Mycol. Res. 113:117, 2009.

Platanus × acerifolia (Aiton) Willd. (London planetree) is a tree commonly used as an ornamental and in the furniture industry. In the summer of 2013, powdery mildew was observed on shoots of P. × acerifolia plants in the cities of Pelotas and Canela (State of Rio Grande do Sul, Brazil). Voucher specimens (n = 2) were deposited in the Phytopathological Museum Manoel Alves Oliveira at Federal University of Pelotas. Dense white powdery masses of conidia and mycelium were observed on leaves (abaxial and adaxial surfaces), petioles, and young stems. Leaves with high disease severities (≥70%) were deformed with curved edges to the adaxial side, and they often died. Mycelia were superficial with lobed appressoria. Conidiophores were straight, sometimes curved at the base, unbranched, cylindrical, 98 to 236 μm long (137.3 ± 41.2 μm) and composed of a cylindrical foot cell 49 to 102 μm long (66.9 ± 19.5 μm) and 4.4 to 6.4 μm wide (5.3 ± 0.8 μm) followed by two to four cells. Conidia were produced singly or in short chains (two to three), without distinct fibrosin bodies, ellipsoid to ovoid and measuring 24 to 37 μm long (29.5 ± 3.2 μm) and 12 to 19 μm wide (15.2 ± 1.4 μm), often with a wrinkled appearance. Primary conidia had truncate bases and rounded apex while both base and apex were truncated in secondary conidia. Germ tubes were produced apically (pseudoidium type). Chasmothecia were not observed. Genomic DNA was used to amplify the internal transcribed spacer (ITS) region using the ITS1 and ITS4 primers. The resulting sequence (602 bp) was deposited (Accession No. KF499270) in GenBank. BLASTn searches revealed similarity of 100 and 99% with Erysiphe platani from P. orientalis L. (Accession No. JQ365943.1) and P. occidentalis L. (Accession No. JX997805.1), respectively. Phylogenetic analysis placed our sequence in a clade (99% bootstrap support) which included only other E. plantani sequences. In short, morphological and molecular approaches allowed us to identify the infecting fungus as E. platani. For Koch's postulates, 10 detached leaves were inoculated (10 to 15 conidia cm2) on their adaxial surface using an eyelash brush. Non-inoculated leaves served as control. All leaves were kept inside trays with petiole immersed in humidified cotton and maintained at 25 ± 1°C. Symptoms identical to those of the original leaves were observed 6 to 8 days after inoculation, whereas the control leaves remained symptomless. Although E. platani has been previously reported on P. × acerifolia in the city of Poços de Calda, state of Minas Gerais, Brazil (1) and on P. occidentalis in Korea (2), to our knowledge, this is the first record of E. platani on P. × acerifolia in Rio Grande do Sul, Brazil. References: (1) E. M. Inokuti et al. New Dis. Rep. 15:38, 2007. (2) Y. J. La and H. D. Shin. Plant Dis. 97:843, 2013.

O objetivo com essa pesquisa foi elucidar o efeito da severidade e da localização da mancha púrpura no tegumento de sementes de soja na qualidade fisiológica e no desenvolvimento inicial da plântula. Sementes da cultivar de soja M5947 IPRO foram separadas em quatro classes de severidade da mancha púrpura: classe 1 – sementes assintomáticas, classe 2 – pigmentação purpúrea na porcentagem de 0,1 a 10%, classe 3 – 10 a 50%, e classe 4 – 50 a 100%. Os tratamentos foram organizados em delineamento inteiramente casualizado. A severidade da mancha purpura na semente não influenciou os valores de condutividade elétrica e a emergência da plântula em solo. Em relação ao teste de envelhecimento acelerado, não ocorreu variação significativa entre as diferentes classes de severidade da mancha purpura, exceto pelo maior comprimento da raiz e a menor porcentagem de sementes mortas na classe 3 comparada a classe 4. Por outro lado, maior porcentagem de plântulas anormais foi observada para sementes com o sintoma da doença associado ao hilo. Sementes com mancha púrpura, independente da severidade da mancha púrpura, não sofrem perdas na sua qualidade fisiológica. Porém, quando o sintoma da doença está associado ao hilo, há maior porcentagem de plântulas anormais no teste de emergência em solo.

Ryegrass (Lolium multiflorum L.) is a forage species with a high content of protein and good palatability and digestibility. In winter, it is frequently used in southern Brazil as feed for livestock. The high humidity in this region is propitious for gray leaf spot, a disease caused by Pyricularia oryzae, considered to be the region’s main biotic problem. In this study, we aimed to evaluate the effect of three types of management, namely seed coating with Trichoderma atroviride (T), application of silicon in the soil (Si), and combination of both treatments (TSi), to reduce the severity of gray leaf spot. In the first phase, the capacity of 10 native isolates of Trichoderma spp. were evaluated in vitro for direct inhibition of P. oryzae based on tests of dual cultures (DC), antibiosis for volatile (Vol), and non-volatile compounds (Nvol). In vivo trials involved the ability to induce resistance responses, such as quantifying severity (SEV) and number of lesions (NL) per cm2 of leaf area. In the second phase, the efficacy of T, Si, and TSi was tested under greenhouse conditions. The lesion expansion rate (LER), relative efficiency of infection (RIE), SEV and NL were measured (after inoculation with P. oryzae), and in parallel the activities of the enzymes superoxide dismutase (SOD), catalase (CAT), peroxidase (POX) and phenylalanine ammonia-lyase (PAL) were quantified (at 24, 48, 72, and 96 h). The strain TR10 (identified by polyphasic taxonomy as T. atroviride) showed one of the highest inhibition values in Vol (23%) and DC (35%). Plants from seeds treated with the strain TR10 had the lowest levels of SEV (5.5%) and NL (3), in contrast with the other strains according to analysis of variance. Under greenhouse conditions, significant differences (P

The silicon (Si) reduced tan spot ( Pyrenophora tritici-repentis ) severity up to 40%, through both biochemical defense mechanisms and histo-cytological defense responses. The activities of enzymes involved in plant defense system such as superoxide dismutase, peroxidase and chitinase showed greater activity in inoculated plants supplied with Si. Histo-cytological analysis indicated that Si potentiated the accumulation of hydrogen peroxide in the beginning of infection process. Together, these defense mechanisms resulted in the reduction of cell death at the infection sites in plants supplied with Si, which in turn showed lower disease severity. Si appears to be a promising alternative control measure for use in integrated management of tan spot.

Our study surveyed Meloidogyne spp. from tobacco cultivars in Brazil carrying the Rk gene, which confers resistance to Meloidogyne incognita races 1 and 3. Identification of Meloidogyne populations from 39 tobacco fields was based on the analysis of esterase phenotypes, perineal patterns, and 18S-internal transcribed spacer (ITS)1-5.8S ribosomal RNA sequences. Biometric characterization and differential host tests of isolates were determined as well. We detected M. incognita, M. javanica, M. enterolobii, M. arenaria, and M. inornata in 18 (46.2%), 16 (41%), 10 (25.6%), 2 (5.1%), and 1 (2.6%) samples, respectively. Mixtures of species were found in 25.6% of the samples. This is the first report of M. inornata parasitizing tobacco in Brazil’s southern region. Two morphological and biochemically unusual populations had host ranges and ITS1 sequences nearly identical to M. enterolobii and M. incognita, respectively. Pathogenic and biometric intraspecific variations were observed. Based on our results and considering the limited efficiency of the Rk gene, it is indispensable not only to search for resistance sources to M. incognita virulent strains but also to consider resistance to M. enterolobii, M. inornata, M. arenaria, and M. javanica in tobacco breeding programs. Changes in integrated management procedures should be considered to avoid increased crop damage in the future.

Rice plants cultivated under 700 ppm atmospheric CO2 concentration presented a reduction in the progress and severity of the brown spot disease (Bipolaris oryzae), through the enhancement of biochemical defense mechanisms. Plants exposed to 700 ppm of CO2 had higher activity of the enzymes superoxide dismutase, catalase, ascorbate peroxidase, peroxidase, polyphenoloxidase and chitinase, and increased phenolic compounds and lignin concentration, independent of the rice cultivar. Therefore, the lower severity values of the disease were related to changes in the development of the lesions as a result of the defense responses, which were stimulated in the rice plants by the increase of CO2 concentration.

The objective of this research was to evaluate the effect of treating oranges with potassium chloride (KCl), potassium hydroxide (KOH) and potassium silicate (K2O3Si) for green mold caused by Penicillium digitatum. The experimental design was completely randomized with five treatments and four replications, each with twenty fruits. For the experiment, the fruits were washed, superficially disinfected and pierced with a needle (2–3 mm deep). After 24 hours, the fruits were treated with inorganic salts or distilled water (control) and, 2 hours later, inoculated with 15 μL of P. digitatum spore suspension. Green mold incidence, rate of lesion expansion, lesion size and sporulation area were evaluated at 96, 120 and 245 ha. At 245 hours after inoculation (hai), the KOH and K2O3Si (50 g.L-1) treatments were the most effective, affecting all evaluated variables and reducing the disease incidence by 80% and 36%, respectively, compared to the control. However, the KOH treatment caused wrinkling and dehydrated the peel, affecting the visual quality of the fruits. In conclusion, among the tested inorganic salts, the K2O3Si treatment (50 g.L-1) reduced the green mold in the citrus without negatively effecting fruit appearance, which indicates that this treatment is an option as a complementary measure to manage the disease. O objetivo da pesquisa foi avaliar o efeito da aplicação dos sais inorgânicos cloreto de potássio (KCl), hidróxido de potássio (KOH) e silicato de potássio (K2O3Si) sobre laranja no controle do bolor verde causado por Penicillium digitatum. O delineamento experimental utilizado foi inteiramente casualizado com cinco tratamentos e quatro repetições, cada uma composta por vinte frutos. Os frutos foram lavados, desinfestados e feridos com uma agulha (2-3 mm de profundidade), após 24 h foram tratados com os sais inorgânicos ou água destilada (controle) e 2 h após, inoculados por meio da deposição de 15 µL da suspensão de esporos de P. digitatum. Às 96, 120 e 245 horas após a inoculação (hai) foram realizadas as avaliações de incidência do bolor verde, taxa da expansão da lesão, tamanho da lesão e da área esporulante. Às 245 hai, entre os sais, o KOH e o K2O3Si foram os mais efetivos, afetando todas as variáveis avaliadas, reduzindo a incidência da doença em 80% e 36%, respectivamente, quando comparados à testemunha. Contudo, o tratamento com o KOH afetou a qualidade visual dos frutos, ocasionando enrugamento e desidratação da casca. Desse modo, conclui-se que, entre os sais inorgânicos testados, o K2O3Si (50 g.L-1) apresentou redução no bolor verde sem comprometer a qualidade visual do fruto, podendo ser incluído como uma medida complementar no manejo da doença.

Brown spot, caused by Bipolaris oryzae, is one of the most destructive rice diseases and causes reductions in crop yield and quality. To determine how the disease affects crop grain yield, gas exchange parameters (net carbon assimilation rate [A], stomatal conductance to water vapor [g s ], internal CO2 concentration [C i] and transpiration rate [E]) and chlorophyll a fluorescence parameters (maximum quantum efficiency of photosystem II [F v/F m and F v ′/F m ′], photochemical [q P] and non-photochemical quenching [NPQ] coefficients, yield of PSII electron transport [Φ PSII] and apparent electron transport rate [ETR]) were evaluated on the leaves of non-inoculated and inoculated plants at 144 h after inoculation (hai). Brown spot severity reached 11.4 % in inoculated plants, and significant reductions of A, g s , C i and E (55, 85, 18 and 48 %, respectively), were observed compared with the non-inoculated ones. The F v/F m, F v ′/F m ′, q P, Φ PSII and ETR were reduced by 5, 9, 18, 25, and 26 %, respectively, for the inoculated leaves relative to their non-inoculated counterparts, whereas NPQ increased by 11 %. Thus, brown spot seems to affect the physiology of rice plants at the photosynthesis level by compromising CO2 uptake through a reduction of stomatal conductance. Furthermore, it also negatively impacted some photochemical or biochemical steps of photosynthesis.

The application of silicon to the roots or leaves reduces the severity of powdery mildew (Podosphaera xanthii) in melon but the latter treatment is less effective. This study compared key biochemical defence responses of melon triggered by P. xanthii after root or foliar treatment with potassium silicate (PS). Treatments consisted of pathogen-inoculated or mock-inoculated plants supplied with PS via roots or foliarly, as well as a non-treated control. The activity of defence enzymes and the concentration of phenolic compounds, lignin and malondialdehyde were determined from leaf samples at different time points after inoculation. Pathogen-inoculated plants irrigated with PS showed both an accumulation of silicon and primed defence responses in leaves that were not observed in pathogen-inoculated plants either sprayed with PS or not treated. These responses included the anticipated activity of peroxidase and accumulation of soluble phenols, the activation of chitinase and repression of catalase, and the stronger activation of superoxide dismutase, peroxidase and β-1,3-glucanase. Moreover, the lignin concentration increased in response to inoculation, whereas the malondialdehyde concentration decreased. For the foliar treatment, however, only an increase in lignin deposition was observed compared with the control plants. The results show that silicon strongly plays an active role in modulating the defence responses of melon against P. xanthii when supplied to the roots as opposed to the foliage.

Blueberry (Vaccinium corymbosum) is a plant native to North America, and it was introduced in Brazil in the 1980s in the State of Rio Grande do Sul. Leaves of blueberry showing leaf rust symptoms were observed on a commercial blueberry field, in the municipality of Jaguarao, Rio Grande do Sul, Brazil (32°39′80.93″S, 53°23′12.44″W) ranging from January to February 2017. The disease started as small reddish-brown leaf spots, epiphyllous, gregarious, with hypophyllous yellowish pustules. With disease progression, the leaf spots enlarged, becoming vein delimited, with a reddish-purple halo. At later stages, lesions coalesced, spreading all over the plant, causing severe precocious defoliation (especially on cultivars Jewel and Snowchaser). Pustules were produced abaxially, with abundant sporulation. Urediniospores were ovoid, yellowish-orange, echinulate, 15 to 24 × 10 to 18 μm (n = 53). Telia were not found. Genomic DNA was extracted from urediniospores and used for amplification of the internal transcribed spacer regions and intervening 5.8S nrRNA gene (ITS), using the primers ITS1-F_KYO2 and ITS4. The resulting fragment (465 bp) was sequenced and deposited in GenBank (MH029898). A BLAST search revealed 99% identity with Thekopsora minima (GenBank accession no. HQ661383). Aiming at verifying the correct diagnosis, a Bayesian phylogenetic inference was performed and showed that the Brazilian sample clustered with five other strains from different countries. To fulfill Koch’s postulates, suspension of urediniospores (1 × 10³ spores/ml) was sprayed on leaves of healthy plants. Healthy plants sprayed with water served as a control. After inoculation, plants were kept inside a mist chamber at 95 to 100% relative humidity, temperature at 25°C, and 12-h photoperiod. Symptoms as small, reddish, irregular lesions appeared 7 days after inoculation, and pustules with uredospores and necrosis were observed at 21 days after inoculation. No symptoms occurred on control plants. To the best of our knowledge, this is the first report of blueberry leaf rust caused by T. minima on highbush blueberry in South America. The fungus has been reported on highbush blueberry in China, Japan, Mexico, South Africa, and the United States (Kobayashi 2007; Mostert et al. 2010; Rebollar-Alviter et al. 2011; Shands et al. 2018; Zheng et al. 2017). Although the yield losses were not measured in the present study, the severity observed at the field suggested that the intense and early defoliation significantly reduced the yield potential of the crop. Further studies are needed to properly evaluate the risk of blueberry leaf rust in commercial fields in Southern Brazil.