Ocorrência de declínio dos citros na região Noroeste do Paraná

Abstract

RESUMO -O declínio dos citros é uma anomalia vascular que provoca grandes prejuízos à produção de citros. Sua causa é controversa, e fatores bióticos e abióticos têm sido sugeridos. Embora detectado desde 1979 afetando plantas em pomares do Estado de São Paulo, sua ocorrência ainda não foi relatada em certas regiões produtoras de citros do Brasil. Este trabalho teve como objetivo comprovar, por meio de testes diagnósticos, a ocorrência do declínio dos citros no polo citrícola da região noroeste do Paraná. Foi realizado em pomar experimental de laranjeira 'Valência' (Citrus sinensis L. Osb.) enxertada em limoeiro 'Cravo' (C. limonia Osb.) plantado em 1994 no município de Nova Esperança. Os testes de teor de zinco na madeira e da absorção de água com injeção no tronco confirmaram a presença de declínio dos citros. Os sintomas da doença foram caracterizados por folhas pequenas, sem brilho e com menor turgidez, redução nos fluxos de brotação, morte da extremidade de ramos e redução da produção e do tamanho de frutos. A primeira ocorrência de declínio dos citros foi observada aos sete anos após o plantio, e aos quinze anos atingiu 31% das plantas. Termos para indexação: Citrus sinensis, perda de produtividade, testes de indexação, sintomas. OCCURRENCE OF CITRUS BLIGHT IN THE NORTHWESTERN AREA OF THE STATE OF PARANA, BRAZILABSTRACT -Citrus blight is a vascular abnormality that affects tree production. It is still under debate if it has biotic or abiotic causes. Although it has been detected since 1979 affecting plants in orchards of the State of Sao Paulo, its occurrence was not confirmed in certain citrus producing areas of Brazil. The objective of the present study was to confirm by diagnostic tests the occurrence of citrus blight in the citrus area in the northwestern region of the state of Parana. The study was done at one experimental orchard with 'Valencia' sweet orange (Citrus sinensis L. Osb.) grafted on 'Rangpur' lime (C. limonia Osb.), planted in 1994 and located at Nova Esperança county. The diagnostic tests of zinc content in the trunk of the plant and the injection of water confirmed the presence of citrus blight. The symptoms of plant decline were characterized by small, opaque and less turgid leaves, reduction of new sprout flushes, twig dieback, reduction of crop and production of smaller fruits. The first occurrence of citrus blight was observed seven years after the planting time and at fifteen years it reached 31% of all plants.

IDENTIFICATION AND QUANTIFICATION OF DIFFERENTIALLY EXPRESSED GENES ASSOCIATED WITH CITRUS BLIGHT (Citrus spp.)

“…The citrus blight is an alteration in the normal development of the plant, characterized by accentuated loss of leaves, excess branches and shoots on the trunk, gradual drying of branches, unseasonal flowering, accentuated nutrient deficiencies, accumulation of soluble phenols in the stem, presence of amorphous and/ or filamentous obstructions in the xylem vessels and low production (Baldassari;Goes;Tannuri, 2003;Auler et al, 2011). The affected plants rarely die, but they become economically unviable due to low amount and quality of the produced fruits.…”

“…Although this anomaly has been known for more than a century, the causal agent is still not known (Barrios et al, 2006;Brlansky et al, 2012). There is a lot of controversy related to the involvement of biotic agents as well as abiotic factors (Rossetti, 2001;Auler et al, 2011). That implicates in the inexistence of prophylactic measures for the control of the citrus blight, so that the only recommended practice is the removal of the sick plants when they enter into an economically unviable production phase.…”