Tamanho da amostra para quantificação do diâmetro de lesões de cancro cítrico
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Data
2008-08-01
Autores
Belasque Jr., José
Jaciani, Fabrício José [UNESP]
Marin, Denis Rogério
Barbosa, José Carlos [UNESP]
Título da Revista
ISSN da Revista
Título de Volume
Editor
Sociedade Brasileira de Fitopatologia
Resumo
A estimativa do diâmetro de lesões de cancro cítrico é uma das principais técnicas usadas na avaliação da interação entre isolados x genótipos, na avaliação da resistência varietal e no estudo de aspectos epidemiológicos. No entanto, inexistem informações a respeito do tamanho da amostra para uma adequada quantificação da doença, considerando o diâmetro de lesões. Nesse sentido, o presente trabalho teve como objetivo a determinação do número de amostras para mensurar o diâmetro médio de lesões de cancro cítrico. Foram considerados como fontes de variação três genótipos do hospedeiro, dois métodos de inoculação de Xanthomonas citri subsp. citri e dois avaliadores. As avaliações dos diâmetros foram realizadas considerando ou não o halo amarelo ao redor do tecido necrosado, quando presente. Estimativas do diâmetro de lesões com erros na média inferiores a 3% são impraticáveis em razão do tamanho excessivo da amostra (mais que quarenta lesões/planta). Menores erros na média ocorreram nas estimativas considerando somente o tecido necrosado. Estimativas precisas do diâmetro de lesões, com erros na média inferiores a 10%, podem ser obtidas com tamanhos de amostras entre cinco e quinze lesões/planta, independentemente do genótipo e da idade das lesões.
The estimation of lesion diameter of citrus canker is one of the most common parameters used in the evaluation of the interaction of strains x genotypes, host resistance, and epidemiology. However, there is no information indicating the sample size for adequate disease measurement, considering the diameter of lesions. In the present work, our objective was to determine the number of samples needed to estimate the diameter of citrus canker lesions. The following factors of variation were considered: three host genotypes, two methods of inoculation, and two evaluators. The diameter evaluations were made considering, or not, the yellow halo, when present. Estimates of lesion diameter with average errors smaller than 3% are impracticable because of the excessive sample size (at least forty lesions/plant). Smaller errors occurred when only the necrosis was considered during the evaluations. Precise estimates of lesion diameter, with errors smaller than 10%, are achieved with sample size between five and fifteen lesions/plant, independently of the citrus genotype and age of lesions.
The estimation of lesion diameter of citrus canker is one of the most common parameters used in the evaluation of the interaction of strains x genotypes, host resistance, and epidemiology. However, there is no information indicating the sample size for adequate disease measurement, considering the diameter of lesions. In the present work, our objective was to determine the number of samples needed to estimate the diameter of citrus canker lesions. The following factors of variation were considered: three host genotypes, two methods of inoculation, and two evaluators. The diameter evaluations were made considering, or not, the yellow halo, when present. Estimates of lesion diameter with average errors smaller than 3% are impracticable because of the excessive sample size (at least forty lesions/plant). Smaller errors occurred when only the necrosis was considered during the evaluations. Precise estimates of lesion diameter, with errors smaller than 10%, are achieved with sample size between five and fifteen lesions/plant, independently of the citrus genotype and age of lesions.
Descrição
Palavras-chave
Xanthomonas citri subsp. citri, phytopathometry, Citrus, Xanthomonas citri subsp. citri, fitopatometria, Citros
Como citar
Tropical Plant Pathology. Sociedade Brasileira de Fitopatologia, v. 33, n. 4, p. 317-322, 2008.