The effects of inter-crop cultivation Between rows of citrus crop on spreading of Guignardia citricarpa Ascospores and in the citrus black spot occurrence

This study highlighted the effect of planting coast-cross grass and forage peanut cv. Amarilis between rows of Natal oranges on spreading of Guignardia citricarpa ascospores and consequent citrus black spot control. Treatments evaluated were: 1- conventional cultivation, free of fungicides; 2- conventional cultivation, using protective fungicides; 3- inter-crop cultivation of coast-cross grass between rows of citrus crops and; 4- inter-cropping cultivation of forage peanut between the rows of citrus crops. Quest Volumetric Spore SystemTM traps were set in order to determine the number of ascospores released. A total of 33 inspections were conducted weekly, from the end of August until early September the following year. A diagrammatic scale was used to determine the severity of the disease as well as the percentage of fruits having a commercial standard. The coast-cross grass was more effective in reducing the number of ascospores produced, whose average statistics were lower than in the conventional treatments, free-fungicides. The inter-crop and conventional cultivation method coupled with fungicide treatment was more effective in reducing the severity of citrus black spot symptoms, and differs statistically from the fungicide-free control method. These methods also resulted in a higher percentage of fruits of a commercial standard, ranging from the 89% through the 91% percentile, and the cultivation, free of fungicides, fell within the 73%.

Influência da temperatura do ar de secagem sobre o teor e a composição química do óleo essencial de Lippia alba (Mill) N. E. Brown

Leaves of Lippia alba were submitted to six different drying treatments, using air at ambient temperature and heated up to 80 °C. The essential oil was extracted by steam distillation and analyzed by GC-MS. For the dried leaves, the oil content was reduced by 12 to 17% when compared with the fresh plant (0.66%). The major oil component was citral, representing 76% for the fresh plant, and varying from 82 to 84% for the dried material. These results showed that L. alba can be submitted to a drying process of up to 80 ºC without degradation and/or loss of the major, [LC1] active component.

Desenvolvimento de um spot test para o monitoramento da atividade da peroxidase em um procedimento de purificação

In this work we describe both a chromatographic purification procedure and a spot test for the enzyme peroxidase (POD: EC 1.11.1.7). The enzyme was obtained from crude extracts of sweet potatoes and the chromatographic enzyme purification procedure resulted in several fractions. Therefore a simple, fast and economic spot test for monitoring peroxidase during the purification procedure was developed. The spot test is based on the reaction of hydrogen peroxide and guaiacol, which is catalyzed by the presence of peroxidase yielding the colored tetraguaiacol.

Variabilidade sazonal e biossíntese de terpenóides presentes no óleo essencial de Lippia alba (Mill.) N. E. Brown (Verbenaceae)

The essential oil of the leaves of Lippia alba chemotype linalool-1,8-cineol was extracted by hidrodistillation at different seasons and analyzed by GC/MS. Qualitative and quantitative variations in regard to the period of harvesting have been performed and the results were correlated with meteorological data. The essential oil yield varied from 0.33 to 0.67%. The chemical diversity of the constituents increased throughout the year, being 1,8-cineol and linalool the major components. Possible biosynthetic routes of mono and sesquiterpenoids present in the essential oil are discussed.

Atividade inseticida de óleos essenciais de Pelargonium graveolens l'Herit e Lippia alba (Mill) N. E. Brown sobre Spodoptera frugiperda (J. E. Smith)

Insecticidal activity of essential oils of Pelargonium graveolens, Lippia alba and compounds geraniol, linalool, 1,8-cineole, limonene, carvone, citral and Azamax® were evaluated against Spodoptera frugiperda. Topical application assay showed essential oil of P. graveolens has acute toxicity against Spodoptera frugiperda larvae (third instar) with LD50 1.13 µg/mg per insect and LD90 2.56 µg/mg per insect. Three essential oils of L. alba also exhibited insecticidal activity with LD50 ranging from 1.20 to 1.56 µg/mg per insect and LD90 from 2.60 to 3.75 µg/mg per insect. Geraniol, linalool, carvone and citral caused significant mortality of 30, 90, 84 and 64% respectively, compared to negative control. The bioinsecticide, Azamax®, caused lower mortality than the compounds of the essential oils.

Woody Gall symptoms in different citrus species and varieties artificially colonized by the citrus brown aphid Toxoptera citricidus

Seedlings of 41 different citrus species and varieties were massively colonized with the citrus brown aphid Toxoptera citricidus, obtained from Pêra sweet orange (Citrus sinensis) trees, presenting symptoms of the "Capão Bonito" complex of the Citrus tristeza virus (CTV). The objective was to evaluate resistance or tolerance of the varieties to that virus complex, but even after eight months of inoculation no stem pitting was observed in the plants. Otherwise, the presence of galls similar to those induced by the vein enation-woody gall disease was observed in 73% of the plants of Volkamer Palermo (Citrus volkameriana), 60% of the Volkamer Catania 2, 2% of the Rangpur Lime D.22.30 (Citrus limonia), 13% of the Volkamer Australian Red, the Rangpur Lime hybrid, the Orlando tangelo (Citrus reticulata x Citrus paradisi) and the Florida Rough lemon (C. jambhiri), and 7% of the Carrizo citrange (Poncirus trifoliata x Citrus sinensis). The highest incidence and the largest gall size were observed in the Palermo Volkamer showing that this clone would be the most suitable to be used as an indicator plant in biological indexing tests for the disease. There are no previous reports in the literature about the occurrence of woody galls in Orlando tangelo and Carrizo citrange.

Epidemiology of apple leaf spot

Apple leaf spot (ALS) caused by Colletotrichum spp. is a major disease of apple (Malus domestica) in Southern Brazil. The epidemiology of this disease was studied in experiments carried out in the counties of Passo Fundo and Vacaria, State of Rio Grande do Sul, from February 1998 to October 2000. The disease was found in all the six apple orchards sampled in the growing seasons of 1997/98 and 1998/99. The fungus isolates associated with ALS fit the characteristics of C. gloeosporioides (75%), C. acutatum (8%), and Colletotrichum sp. (17%). The pathogen overwintered in dormant buds and twigs but not in dropped leaves or fruit mummies. Two sprays of copper oxychloride (at 0.3%) reduced the fungus initial inoculum by 65-84.6% in buds and 85.6-93.7% in twigs, but had no effect on the early season progress of the disease. Disease severity increased proportionally to elevation of temperature from 14 to 26-28 °C. At 34 °C, however, infection was completely inhibited. The duration of leaf wetness required for infection ranged from two hours at 30 °C to 32 h at 16 °C. The relationship of temperature (T) and leaf wetness (W) to disease severity (Y) was represented by the model equation Y = 0.00145[((T-13)1.78)((34.01-T )1.09)] * 25/[1+14 exp(-0.137W)], R² = 0.73 and P < 0.0001. Currently, this information is being used to manage the disease and to validate a forecast system for ALS.

Caracterização do Tomato chlorotic spot virus isolado de jiló no Vale do Paraíba, Estado de São Paulo

Os tospovírus são responsáveis por perdas significativas em diversas culturas, principalmente solanáceas. No município de São José dos Campos (SP), plantas de jiló (Solanum gilo) apresentando sintomas de mosaico, bolhosidades, nanismo e queda acentuada da produção foram coletadas para análise. Visando a caracterização do agente causador dos sintomas, testes biológicos, elétrono microscópicos, sorológicos e moleculares foram realizados. Através de inoculação mecânica em plantas indicadoras das famílias Amaranthaceae, Chenopodiaceae e Solanaceae obtiveram-se resultados típicos aos esperados para tospovírus. Ao microscópio eletrônico de transmissão, observaram-se, em contrastação negativa, partículas pleomórficas com diâmetro entre 80 e 110 nm e em cortes ultra-finos partículas presentes em vesículas do retículo endoplasmático. Através de DAS-ELISA, identificou-se o Tomato chlorotic spot virus (TCSV). A partir de RNA total extraído de folhas infetadas, amplificaram-se, via RT-PCR, fragmentos correspondentes ao gene da proteína do capsídeo (cp) os quais foram seqüenciados e comparados com outros depositados no "GenBank". A homologia de nucleotídeos e aminoácidos deduzidos foi respectivamente de 99 e 95% quando comparada com seqüências de isolados de TCSV. A comparação com as outras espécies do gênero Tospovirus apresentou valores de homologia entre 72 e 84%. Estes resultados confirmam a identidade deste vírus como pertencente à espécie TCSV, que é predominante no Estado de São Paulo e importante patógeno de outras plantas cultivadas. Além disso, variedades de jiló quando inoculadas foram susceptíveis tanto ao TCSV como às espécies Tomato spotted wilt virus (TSWV) e Groundnut ringspot virus (GRSV).

Mycovellosiella robbsii sp. nov. causing leaf-spot on Mimosa caesalpiniaefolia

This is a description of the new species Mycovellosiella robsii, a cercosporoidal hyphomycete, associated with leaf spots on Mimosa caesalpiniaefolia, an important hedge plant with multiple uses in Brazil. The new species was compared to other cercosporoid species associated with plants of the genus Mimosa and other species of the genus Mycovellosiella described on legumes, and is recognized as a distinct taxon. Koch's postulates were carried out and the disease was reproduced by inoculating healthy plants with mycelial suspension or disk, confirming the pathogenicity. This is the first report of a fungal disease on this host.

Three new pathogens infecting antilles cherry in the State of Pará

When grown in monoculture, Antilles cherry (Malpighia glabra) plants have been affected by diseases which cause fruits malformation and spotting, reducing their value for market. From 1999 on, three new diseases characterised by leaf spot and fall of leaves have been observed in plantations located in Santa Izabel do Pará and Igarapé Açu counties. After isolation and pathogenicity tests on leaves of Antilles cherry plants, the isolates were identified as Calonectria ilicicola (anamorph: Cylindrocladium parasiticum) which causes large leaf spots reaching up to 7 cm long, brownish in colour, coalescent, scorching large leaf areas and causing 50% of leaf fall; Corynespora cassiicola, which provokes irregularly shaped, necrotic leaf spots with dark brown margins and white centers, surrounded by a yellow halo; and Myrothecium roridum which causes greyish target spots. Corynespora cassiicola has been reported causing leaf spots on different hosts in the Amazon region, while C. cassiicola has been recorded infecting Antilles cherry besides other hosts in the States of Maranhão and Pará.

Tomato chlorotic spot virus in hydroponically-grown lettuce in São Paulo State, Brazil

In the regions of Campinas and Sumaré, São Paulo, Brazil, hidroponically grown crops of Lettuce (Lactuca sativa) cv. Verônica, which showed virus-like symptoms were examined by electron microscope, biological, serological and molecular tests. Pleomorphic, enveloped particles (80-100 nm in diameter) were always detected in these samples. Experimentally inoculated host plants, including lettuce, reacted with tospoviruses-induced symptoms. Some differences were observed in Gomphrena globosa, which reacted by showing local lesions and systemic mosaic. Two isolates of Tomato chlorotic spot virus (TCSV) were identified by DAS-ELISA and by RT-PCR. The sequencing and alignment of the RT-PCR coat protein amplified fragments have indicated a high degree of homology with the TCSV sequences stored in the GenBank. This is the first report of losses due to a virus from the genus Tospovirus in commercial hydroponic lettuce crops in Brazil. Further epidemiological studies are needed for better understanding the spread of the virus in hydroponic crops, since Tomato spotted wilt virus (TSWV) is reported to spread through the nutritive solution.