A Vis/NIR spectra-based approach for identifying bananas infected with Colletotrichum musae.

Introduction: Anthracnose of banana caused by Colletotrichum species is one of the most serious post-harvest diseases, which can cause significant yield losses. Clarifying the infection mechanism of the fungi using non-destructive methods is crucial for timely discriminating infected bananas and taking preventive and control measures. Methods: This study presented an approach for tracking growth and identifying different infection stages of the C. musae in bananas using Vis/NIR spectroscopy. A total of 330 banana reflectance spectra were collected over ten consecutive days after inoculation, with a sampling rate of 24 h. The four-class and five-class discriminant patterns were designed to examine the capability of NIR spectra in discriminating bananas infected at different levels (control, acceptable, moldy, and highly moldy), and different time at early stage (control and days 1-4). Three traditional feature extraction methods, i.e. PC loading coefficient (PCA), competitive adaptive reweighted sampling (CARS) and successive projections algorithm (SPA), combining with two machine learning methods, i.e. partial least squares discriminant analysis (PLSDA) and support vector machine (SVM), were employed to build discriminant models. One-dimensional convolutional neural network (1D-CNN) without manually extracted feature parameters was also introduced for comparison. Results: The PCA-SVM and·SPA-SVM models had good performance with identification accuracies of 93.98% and 91.57%, 94.47% and 89.47% in validation sets for the four- and five-class patterns, respectively. While the 1D-CNN models performed the best, achieving an accuracy of 95.18% and 97.37% for identifying infected bananas at different levels and time, respectively. Discussion: These results indicate the feasibility of identifying banana fruit infected with C. musae using Vis/NIR spectra, and the resolution can be accurate to one day.

Antifungal sesquiterpenes with post-harvest anthracnose control effect on bananas from the fungus Fusarium lateritium.

To search for antifungal leads, the metabolites of an insect-derived fungus Fusarium lateritium ZMT01 were investigated, providing five sesquiterpenes (1-5), including new molecules microsphaeropsisins D and E (1 and 2). The evaluated antifungal activities in vitro which are higher than the positive control triadimefon include: 1 and 2 towards Fusarium oxysporum (MICs 50, 25 mg L-1; triadimefon 100 mg L-1); 1, 2, 4 and 5 towards Penicillium italicum (MICs 25, 12.5, 25, 25; triadimefon 50 mg L-1), 1, 2 and 4 towards Colletotrichum musae (MICs 25, 12.5, 25; triadimefon 80 mg L-1), 2 and 4 towards Fusarium graminearum (MICs 100, 100; triadimefon 150 mg L-1). The bioassay in vivo displayed that the banana anthracnose control effect of 2 (100 mg L-1) was also higher than that of triadimefon (Inhibition ratios 27.5 ± 2.5%, 55.3 ± 1.4%, 52.1 ± 1.3% for 2, 22.5 ± 2.1%, 47.2 ± 2.0%, 36.6 ± 2.2% for triadimefon at 4 d, 8 d and 12 d, respectively).[Formula: see text].

Antagonistic activity of bacteria from wild honey against Colletotrichum musae, and testing of wild honey as biopesticide spray to control banana anthracnose

Anthracnose is a foliar and fruit disease caused by Colletotrichum spp. affecting a wide range of crops. Infection occurs early followed by quiescence in fruits, such as in banana, where chemical-based pesticides are used as a dependable fungal control for many years. There is an increasing need for a safe control and as implicated in the Organic Agriculture Act of 2010 (RA 10068) in the Philippines. This scenario drove the use of alternative pest control such as the use of biologicals and natural products. In this study, seven bacteria were isolated from wild honey, produced by Apis mellifera, wherein four (BC2, BC3, BC6 and BC7) were found to be an effective antagonist against Colletotrichum musae in in vitro conditions. These bacteria were identified to belong to the genus Lactobacillus spp. (BC2, BC3, BC7) and Bacillus spp. (BC6) based on sugar utilization tests, morphological and cultural growth in PDPA. For the in vivo test, different dilutions of wild honey were used and it was found out that lower concentrations were effective as biopesticide spray to prevent anthracnose infection. Lastly, we report herewith the first isolation of bacteria with biological control potential from wild honey, and to apply the raw or natural product as biopesticide in postharvest fruits.

Antifungal Activity of an Endophytic Fungus Aspergillus versicolor DYSJ3 from Aphanamixis grandifolia Blume against Colletotrichum musae.

An endophytic fungus strain DYSJ3 was isolated from a stem of Aphanamixis grandifolia Blume, which was identified as Aspergillus versicolor based on the morphological characteristics, internal transcribed spacer (ITS) and calmodulin gene sequences analyses. A. versicolor DYSJ3 exhibited strong antagonistic activity against Colletotrichum musae, C. gloeosporioides and Fusarium oxysporum f. sp. cubense with the inhibition rates of 61.9, 51.2 and 55.3% respectively. The antifungal metabolites mainly existed in the mycelium of A. versicolor DYSJ3, and its mycelial crude extract (CE) had broad-spectrum antifungal activities against plant pathogenic fungi. The CE had a good thermal stability, and the inhibition rate of 100 µg/mL CE against C. musae was above 70.0% after disposing at 120 °C for 1 h. Five secondary metabolites were isolated from the CE and identified as averufanin, ergosterol peroxide, versicolorin B, averythrin and sterigmatocystin. Activity evaluation showed versicolorin B exhibited inhibitory effects on the mycelial growth and conidial germination of C. musae, and sterigmatocystin had a weak inhibitory effect on the mycelial growth of C. musae.

A comparative study of the antifungal activity of essential oils of Varronia curassavica Jacq. obtained by different distillation methods / Estudo comparativo da atividade antifúngica dos óleos essenciais de Varronia curassavica Jacq. obtidos por diferentes métodos de destilação

This work aimed to compare the antifungal activity of the essential oil of Varronia curassavica obtained by hydrodistillation and microwave against the fungus Colletotrichum musae and verify the alterations caused by these extraction methods on the leaf surface. This study used four essential oil samples obtained by different methods, two by hydrodistillation [HD1 (1.0 L of water and 100 min.) and HD2 (2.0 L of water and 140 min.)] and two by microwave [MI1 (500W, 20 min, without water) and MI2 (700W, 40 min, with 50 mL of water added to fresh leaves)]. Essential oils concentrations of 0.05, 0.1, 0.5, 1.0, and 3.0% (v / v) were tested in PDA medium. The mycelial growth of C. musae was evaluated by measuring the diameter, every 24 hours up to 144 hours after the beginning of the incubation. Untreated leaves and leaves treated with HD1 and MI1 were prepared for observation in a scanning electron microscope (SEM) LEO EVO 40. The most abundant compounds detected in the essential oil samples analyzed by gas chromatography were: shyobunol, germacrene D-4-ol, E-caryophyllene, bicyclogermacrene, and α-cadinol. Up to 72 hours after the beginning of the incubation, C. musae presented no mycelial growth, even at the lowest essential oil concentration. Conversely, mycelial growth was detected in the control (PDA + DMSO) from 24 hours after incubation. At 144 hours after incubation, regardless of the concentration, the essential oil samples obtained by HD provided lower mycelial growth of C. musae (1.49 cm) when compared with samples obtained by MI (1.80 cm). This difference possibly occurred due to the reduction to less than half of the germacrene D-4-ol content in the samples obtained by MI. The four essential oil samples tested inhibited the mycelial growth and thus presented a inhibitory effect on C. musae. The SEM revealed more drastic changes on the surface of the leaf treated with MI than on those treated with HD. The essential oil of V. curassavica, mainly when obtained by hydrodistillation, has the potential for use in the control of C. musae.

O objetivo do trabalho foi comparar a atividade antifúngica do óleo essencial de Varronia curassavica obtido por hidrodestilação e micro-ondas frente ao fungo Colletotrichum musae e verificar as alterações que esses métodos de extração causam na superfície da folha. Quatro amostras de óleo essencial obtidas em diferentes condições foram utilizadas. Sendo duas por hidrodestilação, HD1 (1,0 L de água e 100 min.) e HD2 (2,0 L de água e 140 min.); e duas por micro-ondas, MI1 (500W, 20 min. sem adição de água) e MI2 (700W, 40 min. com adição de 50 mL de água às folhas frescas). Foram testadas as concentrações 0,05; 0,1; 0,5; 1,0 e 3,0 % (v/v) de óleo essencial em meio BDA. O crescimento micelial do C. musae foi avaliado por medições do diâmetro, a cada 24 horas até 144 horas após o início da incubação. Folhas sem qualquer tratamento e após os tratamentos HD1 e MI1 foram preparadas para observação em microscópio eletrônico de varredura (MEV) LEO EVO 40. Os compostos mais abundantes nas amostras de óleo essencial analisadas por cromatografia gasosa foram: shyobunol, germacreno D-4-ol, E-cariofileno, biciclogermacreno e α-cadinol. Até 72 horas após o início da incubação, não foi observado nenhum crescimento micelial do C. musae, mesmo nas concentrações mais baixas de óleo essencial, enquanto, para o controle (BDA + DMSO), foi observado crescimento do fungo a partir de 24 horas. Após 144 horas, independentemente da concentração, as amostras de óleo essencial obtidas por HD proporcionaram menor crescimento micelial do C. musae (1,49 cm) quando comparadas às amostras obtidas por MI (1,80 cm). Possivelmente essa diferença ocorreu devido à redução para menos da metade, do teor de germacreno D-4-ol, nas amostras obtidas por MI. As quatro amostras de óleo essencial testadas foram capazes de inibir o crescimento micelial, apresentando portanto, um efeito inibitório sobre o C. musae. Alterações mais drásticas observadas através da MEV foram visualizadas na superfície da folha submetida ao processo de extração por MI em comparação à HD. O óleo essencial de V. curassavica, sobretudo o obtido por hidrodestilação, apresenta potencial para o controle de C. musae.

Antifungal activity of Brazilian red propolis extract and isolation of bioactive fractions by thin-layer chromatography-bioautography.

OBJECTIVES: This study set out to highlight the in vitro and in vivo antifungal activity of an Ethanolic Extract of Red Brazilian Propolis (EERBP) and identify bioactive fractions effective against Colletotrichum musae. METHODS: Active fractions were detected by the thin-layer chromatography-bioautography method and characterised by HPLC-MSn. RESULTS: The in vitro results showed that EERBP had strong antifungal properties againstC. musae (81 ± 1% inhibition at 1.6 g GAE L-1). Medicarpin, (3S)-vestitol and (3S)-neovestitol were the main compounds identified in the EERBP extract (45% of all detected peaks). Two isolated fractions displayed inhibition percentages of 35 ± 4 and 42 ± 1%, respectively, on C. musae mycelial growth compared to the EERBP extract. The biological activity of the two fractions displayed an additive effect. CONCLUSION: A further in vivo investigation revealed that EERBP is a potential natural alternative for controlling banana crown rot.

Antifungal activity of essential oils of Myrcia ovata chemotypes and their major compounds on phytopathogenic fungi / Atividade antifúngica de óleos essenciais de quimiotipos de Myrcia ovata e seus principais compostos em fungos fitopatogênicos

This work evaluated the antifungal activity of essential oils of Myrcia ovata chemotypes (MYRO-175, MYRO-156, MYRO-154, MYRO-165, and MYRO-015) and their major compounds (linalool, geraniol, citral, and (E)-nerolidol) on the phytopathogenic fungi Fusarium pallidoroseum (which causes melon postharvest rot) and Colletotrichum musae (which causes anthracnose in banana). The essential oils were obtained by hydrodistillation and analyzed by GCMS/FID. To evaluate the antifungal activity, the essential oils and their major compounds were tested at different concentrations (0.1; 0.3; 0.4; 0.5; 0.7; 1.0; 3.0, and 5.0 mL/L). The major compounds found in the essential oils were nerolic acid, linalool, geraniol, citral, and (E)-nerolidol. The essential oils of the plants MYRO-154, MYRO-165, and MYRO-015 had the minimum inhibitory concentration (MIC) (0.3 mL/L) for F. pallidoroseum and the lowest minimum fungicidal concentration (MFC) (0.7 mL/L), for C. musae. Geraniol and citral had the lowest MFC (0.5 mL / L) for the two fungi tested. For F. pallidoroseum, the essential oils of the chemotypes were more effective than their major compounds. Conversely, the major compounds geraniol of the chemotype MYRO-156 (74.37%) and citral were more effective than their respective essential oils for C. musae. (E)-nerolidol and geraniol of the chemotype MYRO-015 (33.15%) were responsible for the antifungal activity of the essential oils of their respective chemotypes.

No presente trabalho avaliou-se a atividade antifúngica de óleos essenciais de quimiotipos de Myrcia lundiana (MYRO-175, MYRO-156, MYRO-154, MYRO-165, and MYRO-015) e seus compostos majoritários (linalol, geraniol, citral e (E)-nerolidol) sobre os fungos fitopatogênicos Fusarium pallidoroseum(causa podridão em frutos de melão) e Colletotrichum musae (causa antracnose em frutos de banana). Os óleos essenciais foram obtidos hidrodestilação e analisados por CGEM/DIC. Para avaliação da atividade antifúngica foram testados os óleos essenciais e os compostos majoritários nas concentrações: 0,1; 0,3; 0,4; 0,5; 0,7; 1,0; 3,0 e 5,0 mL/L. Os principais compostos presentes nos óleos essenciais foram o ácido nerólico, o linalol, o geraniol, o citral e o (E)-nerolidol. Os óleos essenciais das plantas MYRO-154, MYRO-165 e MYRO-015 apresentaram CIM de 0,3 mL/L e a planta MYRO-015 apresentou a menor concentração fungicida mínima (CFM) (1,0 mL/L). O geraniol e o citral foram os compostos que apresentaram o menor valor de CFM, 0,5 mL/L, frente aos dois fungos testados. O óleo essencial dos quimiotipos testados foram mais promissores que seus componentes majoritários puros, frente o F. pallidoroseum. Já para o C. musae, os componentes majoritários geraniol do quimiotipo MYRO-156 (74,37%) e o citral foram mais promissores que seus respectivos óleos essenciais. Já o (E)-nerolidol e o geraniol do quimiotipo MYRO-015 (33,15%) foram os responsáveis pela atividade antifúngica apresentada pelos óleos essenciais dos respectivos quimiotipos.

Essential oils of Myrcia lundiana Kiaersk and their major compounds show differentiated activities against three phytopathogenic fungi / Óleos essenciais de Myrcia lundiana Kiaersk e seus compostos majoritários apresentam atividades diferenciadas sobre três fungos fitopatogênicos

The present study evaluated the antifungal activity of the essential oils of chemotypes of Myrcia lundiana and their major compounds on the fungi Fusarium pallidoroseum, Fusarium solani, and Colletotrichum musae. The essential oils were obtained by hydrodistillation and analyzed by GCMS/FID. For the evaluation of the antifungal activity, the essential oils and the major compounds were tested at the concentration of 0.1 mL/L until the fungicidal effect was detected. The major compounds detected in the essential oil were 1,8-cineole, isopulegol, and citral. The chemotypes (MLU-005 and MLU-019) provided 100% mycelial growth inhibition for the fungus F. pallidoroseum from the concentration of 1.1 mL/L (minimum inhibition concentration - MIC). For chemotype (MLU-022), the minimum fungicidal concentration (MFC) was 0.3 mL/L. For F. solani, the essential oils of the chemotypes (MLU-005 and MLU-019) presented MIC at concentrations of 7.0 and 5.0 mL/L, respectively. The essential oil of the chemotype (MLU-022) presented MFC of 0.6 mL/L. Different MIC was observed for the three studied chemotypes for the fungus C. musae, ranging between 0.4 mL/L, for the chemotype (MLU-005); 0.5 mL/L, for the chemotype (MLU-022); and 0.7 mL/L, for the chemotype (MLU-019). The best MFC was observed for the chemotype (MLU-005) (0.5 mL/L). The major compounds tested separately presented better MIC values when compared with their chemotypes, except for the compound 1,8-cineole, which presented lower mycelial growth inhibition for the three fungi tested, suggesting that the chemical profile or the presence of some other compound of the essential oil may inhibit the growth of the three fungi studied. The compound isopulegol provided lower MFC for the fungus C. musae (0.4517 mL/L) when compared with the fungi F. pallidoroseum and F. solani, (MFC of 0.4927 mL/L). The compound citral provided a lower MFC on the fungus C. musae (0.1668 mL/L) in relation to the other fungi tested. The essential oils of the chemotypes of M. lundiana and their major compounds showed potential to control the studied phytopathogens and can be an alternative for agriculture for presenting an inhibitory and fungicidal effect against these organisms at lower concentrations.

O presente trabalho avaliou a atividade antifúngica de óleos essenciais de quimiotipos de Myrcia lundiana dos seus compostos majoritários sobre os fungos Fusarium pallidoroseum, Fusarium solani e Colletotrichum musae. Os óleos essenciais foram obtidos por hidrodestilação e analisados por CGEM/DIC. Para avaliação da atividade antifúngica, foram testados os óleos essenciais e os compostos majoritários na concentração de 0,1 mL/L até encontrar o efeito fungicida. Os principais compostos presentes no óleo essencial foram 1,8-cineol, isopulegol e citral. Os quimiotipos (MLU-005 e MLU-019) proporcionaram 100% de inibição do crescimento micelial para o fungo F. pallidoroseum a partir da concentração de 1,1 mL/L (Concentração Inibitória Mínima ­ CIM). Para o quimiotipo (MLU-022), a melhor concentração fungicida mínima (CFM) foi de 0,3 mL/L. Para F. solani, os óleos essenciais dos quimiotipos (MLU-005 e MLU-019) apresentaram CIM nas concentrações de 7,0 e 5,0 mL/L, respectivamente. O óleo essencial do quimiotipo (MLU-022) apresentou CFM de 0,6 mL/L. Observou-se CIM diferenciado para os três quimiotipos estudados para o fungo C. musae, variando entre 0,4 mL/L, para o quimiotipo (MLU-005); 0,5 mL/L, para o quimiotipo (MLU-022); e 0,7 mL/L, para o quimiotipo (MLU-019). O quimiotipo MLU-005 apresentou o melhor CFM, 0,5 mL/L. Os compostos majoritários testados separadamente apresentaram melhores valores de CIM frente aos seus quimiotipos, exceto o composto 1,8-cineol, que apresentou menor inibição do crescimento micelial para os três fungos testados, sugerindo que o perfil químico ou a presença de algum outro composto no óleo essencial pode estar atuando na inibição do crescimento dos três fungos estudados. O composto isopulegol proporcionou menor CFM para o fungo C. musae (0,4517 mL/L) em relação aos fungos F. pallidoroseum e F. solani, para os quais apresentou CFM de 0,4927 mL/L. O composto citral proporcionou um menor CFM sobre o fungo C. musae (0,1668 mL/L), em relação aos demais fungos testados. Os óleos essenciais de quimiotipos de M. lundiana e seus compostos majoritários apresentaram potencial para o controle dos fitopatógenos estudados, podendo ser considerados como uma alternativa para a agricultura, uma vez que em concentrações mais baixas apresentaram efeito inibitório e fungicida frente a estes organismos.

Postharvest control of anthracnose lesions and its causative agent, Colletotrichum musae by some oils.

Anthracnose of banana is incited by Colletotrichum  musae. It is recognized as one the most destructive diseases of mature and immature banana fruits, resulting in huge economic losses all over the world. Present research deals with screening some oils both in vitro and in vivo for their antifungal activity against C.musae. Clove oil (0.1µl/ml) completely arrested the conidial germination and mycelial growth of C. musae. Fenugreek and almond oil exhibited significant inhibition of mycelial growth, 61% and 57% at a concentration of 2µl/ml. However, olive oil was least inhibitory on the test fungi. Clove oil also a showed marked reduction in anthracnose lesions on banana fruits, thereby suggesting disease control. Scanning electron microscopy revealed severely damaged mycelium and conidia. FTIR studies show the presence of important bands representing phenols, terpenes, aldehydes, and ketones. Based on our findings; clove, fenugreek and almond oil demonstrated fungicidal and fungistatic activities against anthracnose pathogen. Hence, these oils can be considered as potential alternatives to chemical treatments.

Banana fruit NAC transcription factor MaNAC5 cooperates with MaWRKYs to enhance the expression of pathogenesis-related genes against Colletotrichum musae.

Plants respond to pathogen attack by the modulation of a large set of genes, which are regulated by different types of transcription factor (TF). NAC (NAM/ATAF/CUC) and WRKY are plant-specific families of TFs, and have received much attention as transcriptional regulators in plant pathogen defence. However, the cooperation between NAC and WRKY TFs in the disease response remains largely unknown. Our previous study has revealed that two banana fruit WRKY TFs, MaWRKY1 and MaWRKY2, are involved in salicylic acid (SA)- and methyl jasmonate (MeJA)-induced resistance against Colletotrichum musae via binding to promoters of pathogenesis-related (PR) genes. Here, we found that MaNAC1, MaNAC2 and MaNAC5 were up-regulated after C. musae infection, and were also significantly enhanced by SA and MeJA treatment. Protein-protein interaction analysis showed that MaNAC5 physically interacted with MaWRKY1 and MaWRKY2. More importantly, dual-luciferase reporter (DLR) assay revealed that MaNAC5, MaWRKY1 and MaWRKY2 were transcriptional activators, and individually or cooperatively activated the transcriptional activities of MaPR1-1, MaPR2, MaPR10c and MaCHIL1 genes. Collectively, our results indicate that MaNAC5 cooperates with MaWRKY1 and MaWRKY2 to regulate the expression of a specific set of PR genes in the disease response, and to contribute at least partially to SA- and MeJA-induced pathogen resistance.

Phyllosticta musarum Infection-Induced Defences Suppress Anthracnose Disease Caused by Colletotrichum musae in Banana Fruits cv 'Embul'.

Anthracnose development by Colletotrichum musae was observed to be significantly less in the fruits of the banana cultivar 'Embul' (Mysore, AAB) infected with Phyllosticta musarum than in fruits without such infections. Anthracnose disease originates from quiescent C. musae infections in the immature fruit. P. musarum incites minute, scattered spots, referred to as freckles, in the superficial tissues of immature banana peel which do not expand during maturation or ripening. P. musarum does not appear to have a direct suppressive effect on C. musae as conidia of C. musae germinate on both freckled and non-freckled fruit forming quiescent infections. Our investigations have shown that P. musarum infection induced several defence responses in fruit including the accumulation of five phytoalexins, upregulation of chitinase and ß-1,3-glucanase, phenylalanine ammonia lyase (PAL) activity and cell wall lignification. (1)H and (13)C NMR spectral data of one purified phytoalexin compared closely with 4'-hydroxyanigorufone. Some of the P. musarum-induced defences that retained during ripening, restrict C. musae development at the ripe stage. This paper examines the potential of P. musarum-induced defences, in the control of anthracnose, the most destructive postharvest disease in banana.

Plant extracts for controlling the post-harvest anthracnose of banana fruit / Extratos de plantas para controle pos-colheita da antracnose da Banana

In banana, fruit rot is incited by Colletotrichum musae which has been the most serious post-harvest disease of immature and mature fruit. The usual control by fungicides prohibited in many countries reduces their commercial value. Therefore, two experiments were conducted to evaluate the antimicrobial activity of alternative products to the synthetic fungicides. First, berries naturally infected by anthracnose were immersed into Azadirachta indica and citric extracts at 2 and 4% (v/v) for 3 minutes and stored for 11 days under environmental conditions. Next, other berries were immersed into essential oil emulsions of Allium sativum, Copaifera langsdorfii, Cinnamomum zeylanicum and Eugenia caryophyllata at 5% for 3 minutes but stored for 11 days. Berries immersed into distilled water were used as control-treatments. The percentage of disease incidence observed in the control-treatment was similar to the ones observed in the extract of A. indica at 2%. The control-treatment showed disease severity of 75.13% and the percentage of disease control was 20.85%. Fruit immersed into distilled water presented less effectiveness than the ones immersed into citric extracts, which promoted the highest effectiveness. Citric extract at 4% was the most efficient treatment because the disease incidence was 19.44%, the disease severity was 9.34% and the disease control was 90.16%. Less severity and, consequently, more disease control were achieved by immersing the berries into the emulsion of essential oil of A. sativum, followed by treatments with C. langsdorfii, E. caryophyllata and C. zeylanicum.

Em pós-colheita, a podridão dos frutos causada por Colletotrichum musae é a doença mais importante da banana (Musa spp.), sendo presente em frutos verdes e maduros, tornando o produto pouco apresentável e inadequado à comercialização. Considerando-se os efeitos prejudiciais à saúde do tradicional método químico de controle e a proibição da utilização de fungicidas em muitos países, objetivou-se no presente trabalho avaliar bioprodutos com atividade antimicrobiana, considerados alternativos para o controle de antracnose em banana em pós-colheita. Os experimentos foram realizados com frutos de banana naturalmente infectados com Colletotrichum musae, submetidos à imersã, em extratos da planta Azadirachta indica e extratos cítricos (Ecolife), nas concentrações de 2 e 4% (v/v), permanecendo por 11 dias em condições ambientes. A emulsão composta de óleos essenciais das plantas Allium sativum, Copaifera langsdorfii, Cinnamomum zeylanicum e Eugenia caryophyllata também foi avaliada quanto a sua eficácia no controle do patógeno, permanecendo em condição ambiente por 11 dias. Frutos tratados com água destilada constituíram o tratamento controle. Os resultados obtidos demonstraram que frutos submetidos ao extrato aquoso de A. indica na concentração de 2% (88,89%) não diferiu do tratamento controle (100% de incidência da doença). O extrato cítrico a 4% promoveu percentuais de incidência, severidade e controle de 19,44; 9,34 e 90,16%, respectivamente, sendo o mais eficiente. Menor percentual de severidade e o maior percentual de controle da doença nos frutos foram proporcionados pela emulsão óleos essenciais de A. sativum, seguidos pelos tratamentos com C. langsdorfii, E. caryophyllata e C. zeylanicum.

Symptomless infection of banana and maize by endophytic fungi impairs photosynthetic efficiency.

Very little is known about the physiological interactions between plant hosts and symptomless endophytic fungi despite their widespread occurrence. We investigated the impact of two such fungi, Colletotrichum musae and Fusarium moniliforme, upon the photosynthetic capacity of two crop plants, banana and maize, respectively. Endophyte-free plants were obtained first and then infected with the fungi. Measurements of total chlorophyll content revealed very little difference between endophyte-free and infected plants of banana, whereas in maize they showed 50% reductions in the endophyte-infected plants. The maximum photochemical capacity (Fv /Fm ) was measured in order to determine if the plants had any photoinhibitory effect caused by biotic or abiotic factors. After 45 d of growth, endophyte-free banana plants had similar values of Fv /Fm to plants typical of nonstressed conditions, whereas the endophyte-infected plants showed a reduction of approx. 15%. Unlike banana, infected maize plants displayed values of Fv /Fm similar to those of control and endophyte-free plants, indicating that the maximum photochemical capacity was not affected by infection. The light response curves of both species showed that the photosynthethic capacity was severely reduced in endophyte-infected plants, reaching saturation at c. 400 µmol m-2 s-1 whereas the control and endophyte-free plants were saturated at much higher photon flux densities. In banana the effect seemed to be due to an impairment of electron transport in the thylakoid membranes. By contrast, reduction of the photosynthetic capacity in maize was due to a reduction in chlorophyll content, leading to a decrease in the electron transport components and a consequent reduction in carbohydrate synthesis. It is possible that the reduction in the maximum yield of photosynthesis in both crops was caused by toxins produced by the fungi. Nevertheless there were no major macroscopic effects on the plants to indicate disease symptoms.

Synthesis of 2-(4-Hydroxyphenyl)naphthalene-1,8-dicarboxylic Anhydride, a Phytoalexin Isolated from Unripe Banana (Musa acuminata).

2-(4-Hydroxyphenyl)naphthalene-1,8-dicarboxylic anhydride, a component of the phytoalexin that has been isolated from the peel of unripe banana (Musa acuminata), was synthesized from 3-bromoacenaphthene.