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Master's Dissertation
DOI
https://doi.org/10.11606/D.11.1992.tde-20220208-014202
Document
Author
Full name
Nivaldo Guirado
Institute/School/College
Knowledge Area
Date of Defense
Published
Piracicaba, 1992
Supervisor
Title in Portuguese
Efeito de choque térmico na expressão de sintomas da sorose dos citros em quatro laranjas doces indicadoras
Keywords in Portuguese
CHOQUE TÉRMICO
LARANJA DOCE
SOROSE DOS CITROS
VIRUS DE PLANTAS
Abstract in Portuguese
Os testes de indexação biológica para a sorose dos citros estão baseados em sintomas foliares especificas. Em São Paulo, estes testes são limitados pela ocorrência de alta temperatura que prevalece na maior parte do ano, e, devido a este fato, sintomas só podiam ser observados durante a brotação da primavera com temperatura amena (±). Visando determinar a possibilidade de que os sintomas da sorose pudessem vir a ser expressados também nos períodos quentes do ano, foram realizados dois experimentos. No primeiro utilizou-se plantas indicadoras de laranjas doces (Citrus sinensis (L.) Osbeck) das variedades Baianinha, do Céu e Madame Vinous enxertadas sobre limão cravo (Citrus limonia (L.) Osbeck) e inoculadas com isolados do vírus da sorose procedentes das laranjas doces Natal e Folha Murcha. As plantas foram formadas em casa-de-vegetação a 30°C, aí permanecendo até que apresentassem em seu ramo de 3 a 4 folhas com 3 a 4 cm de comprimento, sendo nesta fase transferidas para câmaras de crescimento com luminosidade igual e constante, 16 horas por dia fornecida por 8 lâmpadas HO de 85 Watts cada tipo luz do dia e 5 lâmpadas incandescentes de 40 Watts cada. A temperatura das câmaras foi regulada para 15°C, 20°C e 25°C. Observou-se que o choque térmico a 15°C por 3 a 6 dias proporcionou a melhor expressão sintomatológica da sorose; que as CVS Baianinha e do Céu são melhores indicadoras do que a Madame Vinous; e que a procedência do vírus influi na severidade dos sintomas. No segundo experimento, foram empregadas as laranjas doces Baianinha, do Céu, Madame Vinous e Caipira, que foi indicadora padrão em São Paulo. Essas indicadoras foram preparadas de maneira semelhante às do primeiro experimento, enxertadas com borbulhas de plantas de laranja Pera, Natal, Valência e Hamlin suspeitas de estarem infetadas pelo vírus da sorose e submetidas a choque térmico de 15°C. Os resultados obtidos indicaram também nesse caso que o choque térmico de 15°C por 3 a 6 dias comprovou ser o mais adequado para a expressão sintomatológica da sorose; que as laranjas Baianinha e do Céu se mostraram mais eficientes do que a Madame Vinous e Caipira; que das 4 laranjas doces suspeitas, apenas a Valência achava-se infetada pelo vírus, estando as demais (Pera, Natal e Hamlin) sadias.
Title in English
Thermal shock effect on psorosis symptoms expression in four sweet orange indicators
Abstract in English
Biological indexing for citrus psorosis is based on particular foliar symptoms. In the State of São Paulo, the indexing is limited by the occurrence of high temperatures during the most part of the year, and, because of this, the symptoms can only be seen during the spring growth flush when mean temperatures are around 20°C. In order to induce psorosis symptoms on the indicator plants during the warm periods, two experiments were carried out. The indicator plants for the first experiment were sweet oranges (Citrus sinensis (L.) Osbeck) cv. Baianinha, do Céu and Madame Vinous, grafted on lime (Citrus limonia (L.) Osbeck) cv Rangpur. These plants were graft inoculated with psorosis infected buds collected from Natal and Folha Murcha sweet oranges. The plants were kept under greenhouse conditions (average temperature of 30°C) until they had developed 3-4 leaves with 3-4 cm long. The plants were then transferred to growth chambers with 16 hours of light and temperatures adjusted to 15°C, 20°C and 25°C, respectively. Light was supplied by 8 HO lamps of 85 watts and 5 incandescent lamps of 40 watts. It was observed that plants exposed to 15°C for 3-6 days showed the best symptoms of psorosis and that Baianinha and do Céu sweet oranges were better indicator for psorosis than Madame Vinous. Also, the origin of the psorosis virus isolate affected the severity of the symptoms. For the second experiment the same indicator plants mentioned above were used with addition of the Caipira sweet orange which was the standard indicator plant for psorosis in São Paulo. The plants were prepared as described before. Buds from Pera, Natal, Valência and Hamlin sweet oranges suspected to be infected by psorosis virus were used as source of inoculum. Plants were placed in a growth chamber at 15°C and same luminosity as in the first experiment. The results of this experiment confirmed that the thermal shock at 15°C for 3 to 6 days was the most adequate for symptoms expression of psorosis. It was also observed that Baianinha and do Céu sweet oranges were better indicator for psorosis than Madame Vinous, and Caipira sweet oranges. Among the four sweet oranges suspected to be infected by psorosis virus, only Valência was found infected.
 
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