ABSTRACT The use of fuels for agricultural Diesel engines cycle, both of mineral origin (Diesel) or vegetable and animal origin (biodiesel) can significantly alter its performance. Therefore, the aim of this study was to quantify the change in torque, power and consumption of agricultural Diesel engine fuel using minerals and vegetables fuels. It was used a tractor power take-off coupled to a magnetic brake dynamometer (for measuring speed and torque for subsequent calculation of power), and a flow meter (for measuring the hourly fuel consumption and specific fuel consumption calculation). Eleven different fuels (S10 mineral diesel with 5%, 10%, 15%, 20% and 50% biodiesel and mineral diesel S500 with 5%, 10%, 15%, 20% and 50% biodiesel, have been used pure biodiesel B100). The results indicate that the increase of biodiesel in mineral diesel reduces torque and power, increases the specific fuel consumption and practically does not change the hourly consumption. This reduction in torque and power occurs with greater intensity in Diesel S10. Additions of 10% biodiesel in mineral diesel reduces the maximum torque 1.65 Nm (0.6%), the maximum power at 0.33 kW (0.6%) and increases the specific fuel consumption of 3.6 g kWh -1 (1.3%).

RESUMO Na semeadura do arroz irrigado, é necessária a boa drenagem da área, sendo realizados drenos cortando as taipas transversalmente. Para o estabelecimento da lâmina de irrigação definitiva, é necessário o fechamento destes drenos realizado pelos agricultores por meio de diversas maneiras. O estudo de tempos e movimentos de diferentes operações agrícolas é uma importante ferramenta para a obtenção de dados que reflitam o desempenho das mesmas. Dessa forma, o presente trabalho objetivou avaliar o desempenho de cinco equipamentos utilizados na lavoura orizícola, na operação de fechamento de taipas abertas para drenagem (entaipadora de base larga, braço valetador, caçamba "scraper", pá de corte e um protótipo desenvolvido para realizar esta operação), em duas diferentes áreas (coxilha e várzea). Após a avaliação, verificou-se que há diferenças entre os equipamentos utilizados, sendo o protótipo superior aos demais para as variáveis tempo total de operação, eficiência de tempo sem tempo gasto com deslocamento entre taipas, capacidade efetiva de campo e consumo de combustível por taipa.

ABSTRACT A good drainage system is critical during irrigated rice sowing; therefore, earth dikes are built to control water flows. Therefore, irrigation depths can be regulated by these dikes' openings, being performed in a variety of ways. Studying time and motion of different agricultural practices consists of a meaningful tool to gather data on the performance of these mechanisms. Given that, we aimed to test the performance of five equipment used in paddies to close earth dikes opened for drainage purposes (rice-dike plow, ditcher, bucket scraper, cutting shovel and a prototype developed for this operation) in two different areas (hills and lowland). After evaluation, we concluded that there are differences among the assessed equipment and, the developed prototype had the best results for total time of operation, time efficiency, effective field capacity and fuel consumption by dike.

This study aimed to assess the ability of silicon (Si) to potentiate defense enzyme activities in rice leaf sheaths and thus reduce sheath blight, caused by Rhizoctonia solani, development. Rice plants of BR-Irga 409 and Labelle cultivars were grown in a hydroponic solution containing 0 (-Si) or 2 mM (+Si) Si and inoculated with R. solani. Silicon concentration in the leaf sheaths was significantly higher in the +Si plants than the -Si plants by 727% for BR-Irga 409 and 714% for Labelle. The area under relative lesion expansion progress curve was significantly lower for +Si plants than -Si plants, by 34.2% for BR-Irga 409 and 30.59% for Labelle. Increases in the activities of phenylalanine ammonia-lyases, peroxidases, polyphenoloxidases and chitinases in the leaf sheaths of plants supplied with Si, especially of those from BR-Irga 409, led to reduced progress of sheath blight lesions.

Three field experiments were carried out to assess the level of resistance of several cultivars to early blight (EB) and to examine the association between host resistance and either foliage maturity or tuber skin types. A total of 26 cultivars were used in Exps. 1 and 2, and 24 in Exp. 3. Plants were inoculated with isolates of Alternaria grandis at 31 days after planting. EB severity was quantified in each plot every seven days. The approach to determine the resistance levels of potato cultivars was based on multivariate analysis techniques. The tested cultivars responded as either resistant, moderately resistant, moderately susceptible or susceptible to EB. Most of the cultivars were classified as susceptible or moderately susceptible to EB. Resistant cultivars were mid-season, mid-late or late maturity. None of the susceptible cultivars were later maturity (mid-late or late maturity). In most cases, susceptible cultivars were earlier maturity (early or mid-early maturity). Most resistant cultivars had rough, mid-rough or smooth skin. None of the susceptible cultivars had rough skin. In most cases, susceptible or moderately susceptible cultivars had smooth skin. Obtaining potato cultivars that are resistant to this destructive disease will help reduce production costs and the need for costly fungicides.

This study investigated the effects of silicon (Si) on the resistance of common bean plants to anthracnose caused by Colletotrichum lindemuthianum. The plants were grown in a nutrient solution containing 0 (control) or 2 mM Si (+Si) and both photosynthesis and antioxidative metabolism levels were evaluated. The Si concentrations in the leaf tissues of +Si plants increased by 33% in comparison to those of control plants. Anthracnose severity was reduced by 34% in +Si plants in comparison to control plants. The net carbon assimilation rate, stomatal conductance to water vapor and transpiration rate values were significantly higher in +Si plants than in control plants. The activities of superoxide dismutase (SOD), ascorbate peroxidase (APX) and glutathione reductase (GR) tended to be higher in +Si plants than in control plants. The hydrogen peroxide concentration was significantly lower in +Si plants than in control plants. In conclusion, the Si supply was associated with lower anthracnose severity and up-regulation of antioxidant enzymes, which in turn might be associated with better gas exchange in +Si plants. The impaired photosynthetic performance in +Si plants was associated with stomatal limitations, whereas in control plants those impairments likely reflected dysfunctions at the level of biochemical reactions involved in CO2 fixation.

This study investigated the importance of silicon (Si) in rice grain husk in association with fungicide treatment for preventing Bipolaris oryzae transmission from seed to seedling and the improvement in seedling emergence. Plants from cv. Oochikara and its mutant (lsi1 mutant) defective in active Si uptake were grown in nutrient solution without (-Si) or with (+Si) Si and their panicles were inoculated with B. oryzae. Seeds were evaluated for brown spot severity (BSS) and husk Si concentration. The Si concentration in the husks of cv. Oochikara plants was up to four times higher than the lsi1 mutant plants. BSS was significantly reduced in the husks of the seeds obtained from +Si plants, particularly for cv. Oochikara. A higher percentage of seedling emergence occurred for +Si plant seeds, particularly for cv. Oochikara, and a lower percentage of infected seedlings was observed for the +Si cv. Oochikara treatment, particularly for the fungicide treated seeds. Fungicide was not efficient in preventing seedling infection by B. oryzae for seeds with BSS greater than 50%. High Si concentration in the husk resulted in lower BSS and the fungicide efficiency was greater with a low BSS on seeds from +Si plants, particularly for cv. Oochikara.

The objective of this study was to understand the infection process of Fusarium oxysporum f. sp. phaseoli (Fop) in bean cultivars classified as resistant (Manteigão Fosco 11), intermediate (VP8) and susceptible (Meia Noite). Plants of the three cultivars were inoculated at 10 days after emergence with a suspension of 1×10(6) conidia of Fop per mL. At 43 days after the inoculation, stem segments were observed with a scanner electronic microscope. The cultivars Manteigão Fosco 11 and VP8 presented an occluding material in the xylem vessels, which may have restricted tissue colonization by Fop. The resistance of bean cultivars to Fop seemed also to be explained by structural differences in the xylem tissue.

Soil fumigation with the synthetic essential oil of mustard (93% allyl isothiocyanate) (EOM) was evaluated as a substitute of bio-fumigation with cruciferous plant species, using Sclerotium rolfsii and Sclerotinia sclerotiorum as test pathogens, together with its non-target effect on the general population of soil microorganisms. The mortality of the sclerotia of both fungi was dependent upon the concentration of EOM and the exposure period. Exposure to the EOM vapors delayed in vitro germination of the sclerotia.Total germination of the control sclerotia of S. rolfsii, after 120 h incubation, was 94%, of which 88% germinated within 48 h. In contrast, to the total germination of 77% or 47%, less than 3% germinated in 48 h when exposed for 4 or 7 days to 50 µl EOM/L. Exposure to 100 µl/l for 4 or 7 days resulted in the mortality of 50 and 100% sclerotia, respectively. The tendency for delayed germination and mortality was similar for the sclerotia of S. sclerotiorum. No viable sclerotia of either fungus were detected to the depth of 10 cm in the air dried, moist or wet soil fumigated for 7 days with the EOM at the rate of 150 µl/L. In the field plots, no viable sclerotia of S. rolfsii were detected after 7-day exposure to the EOM applied to the upper soil layer at the rate of 9, 12, or 18 ml/m² and covered with a plastic sheet, while 73, 50 and 15%, respectively, were recovered from uncovered plots. In field plots, the fluorescein diacetate hydrolysis decreased by EOM treatment. However, the colony forming units of actinomycetes and bacteria increased, but those of fungi decreased significantly. Soil fumigation with EOM can be used with several advantages, as a substitute of bio-fumigation with cruciferous plant species.

The supply of silicon (Si) to wheat plants may potentiate their resistance against infection by Bipolaris sorokiniana. Considering that there is no information regarding how Si affects the infectious process of this fungus on wheat leaves, this study intended to investigate, using light and scanning electron microscopy, the effects of Si supply on the infection process of B. sorokiniana on wheat leaves at tissue level. For that, leaf segments of -Si and +Si plants were prepared. The number of necrotic brown cells and the degree of browning of necrotic cells were determined for each infection site. As results, it was found that the number of brown epidermal cells and the frequency of infection sites showing browning were significantly lower on leaves of +Si plants. On the leaves of -Si plants, an intense dissolution of the wax layer also occurred and hyphae were found inside the disorganized epidermal cells. On leaves of +Si plants, degradation of the wax layer was observed only in areas close to conidia. Within 96 hours after inoculation, a dense network of hyphae had colonized the leaf surface of -Si plants, in striking contrast to +Si plants, for which only sparse hyphae were found.

The resistance of coffee plants to Meloidogyne exigua is conferred by the gene Mex-1. However, the mechanisms of resistance still need to be clarified. Therefore, the penetration, development and reproduction of two populations of M. exigua (M1, isolated from the coffee plant and M2, from rubber tree) in susceptible (Coffea arabica 'Catuai') and resistant (C. canephora 'Apoatã') cultivars were studied. A greater quantity of J2 from M1 penetrated the susceptible cultivar, but there was no difference between the cultivars for M2. Although the resistant coffee cultivar formed some galls, the nematode did not reproduce. M2 did not induce the formation of galls or the production of eggs in either cultivars. Events related to hypersensitive reaction (HR) were observed as well as other defense responses of the coffee cultivar against M. exigua, which inhibited the formation of the feeding site, provoked emigration of the J2 and delayed or inhibited development and reproduction. The response of the non-host plant was more effective, because it did not allow development of the nematode or, consequently, its reproduction. It was concluded that the coffee cultivar's resistance to M. exigua is not restricted to HR, but rather to a set of defense responses, both constitutive and induced, expressed after nematode penetration, especially phenolic-like compounds.

Em três experimentos, avaliou-se o efeito de pulverizações de ácido jasmônico (AJ), etefon (ET) e acibenzolar-S-metil (Bion®) (ASM) a 0,1 mM, 0,5 mM e 0,3 g L-1, respectivamente, nos componentes de resistência do tomateiro (cv. Santa Clara) à pinta bacteriana, causada por Pseudomonas syringae pv. tomato e na atividade de peroxidases (POX), polifenoloxidases (PFO), β-1,3-glucanases (GLU) e lipoxigenases (LOX). Apenas no experimento 3, o período de incubação aumentou significativamente em um dia nas plantas pulverizadas com ASM, em comparação com as plantas pulverizadas com água (controle). O número de lesões por planta foi significativamente reduzido por AJ, ET e ASM nos três experimentos. Para algumas épocas de avaliação, a atividade de POX, PFO e GLU foram maiores para o AJ; de PFO, GLU e LOX, para o ASM; e de GLU e LOX, para o ET em comparação com o controle. Conclui-se que na presença de AJ, ET e ASM, os sintomas da pinta bacteriana foram reduzidos e a atividade das enzimas POX, PFO, GLU e LOX foram maiores.

Three experiments were performed aimed to evaluate the effect of jasmonic acid (JA), ethephon (ET) and acibenzolar-S-methyl (Bion®) (ASM) sprayed at 0.1 mM, 0.5 mM and 0.3 g L-1, respectively, on the components of resistance of tomato plants (cv. Santa Clara) to bacterial speck caused by Pseudomonas syringae pv. tomato as well as on the activity of peroxidases (POX), polyphenoloxidases (PPO), β-1,3-glucanases (GLU) and lypoxigenases (LOX). Only for experiment 3, the incubation period significantly increased by one day for plants sprayed with ASM compared to plants sprayed with water (control). For all experiments, the number of lesions per plant was significantly reduced by JA, ET and ASM in comparison to the control. For some evaluation times, POX, PPO and GLU activities were higher for JA; PFO, GLU and LOX for ASM; and GLU and LOX for ET in comparison to the control. In conclusion, in the presence of AJ, ET and ASM, bacterial speck symptoms were reduced and the activity of the enzymes POX, PFO, GLU and LOX increased.

O estudo investigou o efeito do silício (Si) e de doses de manganês (Mn) na atividade das enzimas peroxidases (POX), polifenoloxidases (PFO) e fenilalanina amônia-liases (FAL) em plantas não inoculadas e inoculadas com Bipolaris oryzae. Plantas de arroz (cultivar Metica 1) foram cultivadas em solução nutritiva com 0 (-Si) e 2 mmol Si L-1 (+Si) e com as doses de 0,5; 2,5 e 10 µmol Mn L-1. As plantas foram inoculadas com B. oryzae e amostras de folhas foram coletadas às 6, 12, 18, 24, 36 e 48 h após inoculação (hai). Amostras de folhas de plantas não-inoculadas, nestes mesmos tempos, também foram coletadas. Para as doses de 0,5 e 2,5 µmol Mn L-1, a atividade da POX aumentou para as plantas -Si com um pico às 48 hai na dose de 10 mmol Mn L-1. Para as plantas +Si, a atividade da POX também aumentou, mas foi baixa para as doses de 2,5 e 10 mmol Mn L-1. A atividade da POX não foi afetada pelas doses de Mn na presença de Si. No entanto, na ausência de Si a atividade da POX aumentou. Para a dose de 0,5 mmol Mn L-1, a atividade da PFO nas plantas -Si aumentou, mas não foi afetada pelas outras duas doses de Mn, exceto um pico às 18 hai na dose de 10 mmol Mn L-1. Na presença de Si, a atividade PFO aumentou nas plantas que receberam 2,5 mmol Mn L-1 em contraste com as outras duas doses de Mn para as quais a atividade da PFO decresceu. Ao comparar os tratamentos -Si e +Si na dose de 2,5 mmol Mn L-1, atividade da PFO aumentou das 18 às 36 hai para as plantas supridas com Si. A atividade da FAL nas plantas -Si decresceu independentemente das doses de Mn. Nas plantas +Si e inoculadas com B. oryzae, houve menor atividade da FAL tanto na maior quanto na menor dose de Mn e também nas plantas não-inoculadas. A atividade da FAL não aumentou na presença de Si, mas na ausência desse elemento, houve aumento em atividade. Os resultados deste estudo mostram que as atividades da POX, PFO e FAL não aumentaram devido ao suprimento de Si independente da dose de Mn.

This study investigated the role of silicon (Si) and manganese (Mn) rates on the activity of peroxidases (POX), polyphenoloxidases (PPO) and phenylalanine ammonia-lyases (PAL) on rice plants non-inoculated and inoculated with Bipolaris orzyae. Rice plants (cultivar Metica 1) were grown in nutrient solution with 0 (-Si) or 2 mmol Si L-1 (+Si) and with 0.5, 2.5 and 10 μmol Mn L-1. Plants were inoculated with B. oryzae and leaf samples were collected at 6, 12, 18, 24, 36 and 48 h after inoculation (hai). Leaf samples were also collected from non-inoculated plants at these same time-points. POX activity increased for -Si plants inoculated with B. oryzae at both rates of 0.5 and 2.5 µmol Mn L-1 with one peak at 48 hai at 10 µmol Mn L-1. For plants supplied with Si, POX activity also increased, but seemed to be low at the rates of 2.5 and 10 µmol Mn L-1. POX activity did not show to be greatly influenced by the Mn rates in the presence of Si. However, in the absence of Si, POX activity increased. PPO activity on -Si plants increased at the rate of 0.5 µmol Mn L-1 and was not affected by the other two Mn rates, except a peak at 18 hai at the rate of 10 µmol Mn L-1. In the presence of Si, PPO activity increased on plants supplied with 2.5 µmol Mn L-1 in contrast to the other two Mn rates for which the PPO activity decreased. By comparing the -Si and +Si treatments at the rate of 2.5 µmol Mn L-1, PPO activity increased from 18 to 36 hai in the presence of Si than on its absence. PAL activity on -Si plants decreased regardless of the Mn rates. On plants supplied with Si and inoculated with B. oryzae, PAL showed low activity at the highest Mn rate and also at the rate of 0.5 µmol Mn L-1, besides its activity been very low compared to the non-inoculated plants. PAL did not increase in activity in the presence of Si, but on its absence, high levels of activity were achieved. Results from this study showed that the activities of POX, PPO and PAL were not boosted by Si at any Mn rate.

A ferrugem, causada por Hemileia vastatrix, é a principal doença e a que mais reduz a produção do cafeeiro no Brasil. Novos métodos de controle que podem reduzir a intensidade da ferrugem e serem integrados com a resistência genética e o controle químico precisam ser investigados para aperfeiçoamento do seu manejo. Considerando que várias espécies de plantas supridas com silício (Si) apresentam aumento da resistência a diversos patógenos, este estudo examinou o possível efeito do Si em aumentar a concentração de ácido clorogênico (AC) em folhas de cafeeiro e, consequentemente, o nível de resistência à ferrugem. Plantas de cafeeiro (cv. "Catuaí Vermelho IAC 44") crescidas por 35 dias em solução nutritiva contendo 0 (-Si) e 2 mM Si (+Si) foram inoculadas com H. vastatrix. A concentração foliar de Si foi de 0,36 e 0,42 dag/kg e a área abaixo da curva do progresso da ferrugem foi de 154,5 e 119,4, respectivamente, para os tratamentos -Si e +Si, mas não houve diferença significativa entre os dois tratamentos. Para plantas não inoculadas com H. vastatrix, a concentração foliar de AC total e ácido quínico-cafeoil (AQC) foi similar entre os tratamentos -Si e +Si. Embora tenha ocorrido aumento de 236,4 e 257,1%, respectivamente, para AC total e AQC para o tratamento +Si quando comparado ao tratamento -Si aos 30 dias após inoculação com H. vastatrix, a severidade da ferrugem não decresceu, pois o fungo já havia colonizado os tecidos foliares. Assim, independente do aumento na concentração foliar de AC, a resistência do cafeeiro à infecção por H. vastatrix não foi potencializada pelo Si.

Rust, caused by Hemileia vastatrix, is the main disease that decreases coffee production in Brazil. New and enhanced methods to reduce rust intensity that can be integrated with modern genetic and chemical approaches need to be investigated. Considering that many plant species supplied with silicon (Si) show increased resistance to several pathogens, this study examined the possible effect of this element in increasing chlorogenic acid (CA) concentrations in coffee leaves and, consequently, increasing the level of resistance to rust. Plants (cv. "Catuaí Vermelho IAC 44") were inoculated with H. vastatrix after growing for 35 days in a hydroponic culture amended with 0 (-Si) or 2 (+Si) mM Si. Concentration of Si in leaf tissues was of 0.36 and 0.42 dag/kg for -Si and +Si treatments, respectively, but without a statistically significant difference. The area under rust progress curve was 154.5 and 119.4 for -Si and +Si treatments, respectively, but without significant statistical difference. For non-inoculated plants, the concentrations of total CA and caffeoyl-quinic acid (CQA)compounds (diCQA) were similar between -Si and +Si treatments. Even though there was an increase of 236.4 and 257.1%, respectively, for total CA and diCQA for +Si when compared to -Si treatment at 30 days after inoculation with H. vastatrix, reduction on rust severity was not obtained once the fungus had already colonized the leaf tissues. Therefore, regardless of the increase in the concentrations of chlorogenic acid on leaves, coffee resistance to H. vastatrix infection was not potentialized by Si.

Este trabalho objetivou avaliar o potencial do ácido jasmônico (AJ), quitosana desacetilada (QUI), silicato de potássio (SP), acibenzolar-S-metil (ASM), Ethefon (ET) e fosfito de potássio (FP) na redução da severidade da brusone do trigo. O fungicida tebuconazole (TE) e a água destilada (AD) foram utilizados como tratamentos controle. Plantas das cultivares BR 23, BH 1146 e BRS 208 foram pulverizadas com AJ, QUI, SP, ASM, ET, FP, TE e AD 24 h antes da inoculação com Pyricularia grisea. Avaliou-se o período de incubação (PI), a severidade e o efeito fungitóxico dos produtos no crescimento micelial de P. grisea. Para o PI, não houve diferença significativa entre os fatores cultivares e tratamentos, mas para a severidade houve interação entre esses fatores. A menor severidade da brusone para a cultivar BR 23 ocorreu com a pulverização do TE, FP e ET, os quais não diferiram estatisticamente. Para BH 1146, os tratamentos AD, QUI e ASM não diferiram estatisticamente, mas diferiram dos demais tratamentos que apresentaram menor severidade. A aplicação do TE e do FP garantiram uma menor severidade da brusone para a cultivar BRS 208. O FP propiciou uma maior redução da severidade da brusone nos dois cultivares. Os menores valores para o crescimento micelial de P. grisea ocorreram com a adição de TE e SP no meio de cultura. Os resultados desse estudo apontam para o efeito promissor do FP e do ET na potencialização da resistência do trigo à brusone, a qual mostrou ser dependente do nível de resistência basal da cultivar de trigo.

This study aimed to determine the potencial of jasmonic acid (JA), deacetylated chitosan (DC), potassium silicate (PS), Acibenzolar-S-Methyl (ASM), ethephon (ET), and potassium phosphate (PP) on the reduction of blast severity on wheat. The fungicide tebuconazole (TE) and distilled water (DA) were used as control treatments. Plants from the cultivars BR 23, BH 1146, and BRS 208 were sprayed with JA, DC, PS, ASM, ET, PP, TE, and DA 24 h before inoculation with Pyricularia grisea. The incubation period (IP), blast severity, and the effect of the treatments on mycelial growth of P. grisea were evaluated. For the IP, there was no significant difference among cultivars and also for the treatments, but there was interaction between these factors for severity. The lowest severity for BR 23 cultivar occurred with the spray of TE, PP, and ET, which were not significantly different among them. For BH 1146 cultivar, the treatments DA, DC, and ASM were not significantly different among them, but differed significantly from the other treatments to which were obtained the lowest severity. The spray of TE and PP gave the best reduction on severity for BRS 208 cultivar. The PP was the treatment that most reduced severity on the three cultivars tested. The lowest values for mycelial growth of P. grisea occurred upon the addition of TE and PS to the culture medium. The results of this study point to the promising effect of PP and ET in the potentiation of wheat resistance to blast disease, which showed to be dependent on the basal level of resistance of the cultivar.

Este trabalho teve como objetivo estudar o processo infeccioso de Ramularia areola, agente causal da ramulária, em folhas de algodoeiro utilizando-se a microscopia eletrônica de varredura. Plantas de algodoeiro da cultivar Nu-Opal no estádio V4 foram inoculadas com uma suspensão de 1,5 × 10(5) conídios mL-1 de R. areola. Amostras de folhas foram coletadas 12 horas após a inoculação (h.a.i.) e aos 12 e 22 dias após a inoculação (d.a.i.) e preparadas para observação no microscópio eletrônico de varredura. A partir das 12 h.a.i. após a inoculação das plantas, conídios de R. areola germinaram sem a formação de apressório e a maioria deles produziram dois tubos germinativos que cresceram em direção aos estômatos na tentativa de penetrá-los. Aos 12 e 22 d.a.i., as hifas de R. areola colonizaram, inter e intracelularmente, o mesófilo foliar e a esporulação ocorreu através dos estômatos presentes nas faces adaxial e abaxial da epiderme foliar.

This study aimed to elucidate the infectious process of Ramularia areola, the causal agent of ramularia leaf spot, on cotton leaves by using scanning microscopy. Plants from cotton cultivar Nu-Opal at growth stage V4 were inoculated with a 1.5 × 10(5) conidial suspension of R. areola. Leaf samples were collected at 12 hours after inoculation (h.a.i.) and also at 12 and 22 days after inoculation (d.a.i.) and prepared to be observed under scanning electron microscope. At 12 h.a.i., conidia of R. areola started to germinate without formation of appressoria and most of them produced two germ tubes that grew towards the stomata in an attempt to penetrate them. At 12 and 22 d.a.i., hifa of R. areola colonized, inter and intracellularly, the mesophyll cells and sporulation occurred through the stomata present on both adaxial and abaxial leaf epidermis.