Huanglongbing e Diaphorina citri: estudos das relações patógeno-vetor-hospedeiro
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Data
2017-06-26
Autores
Cifuentes Arenas, Juan Camilo [UNESP]
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Universidade Estadual Paulista (Unesp)
Resumo
O huanglongbing (HLB), associada a bactérias de floema (Candidatus Liberibacter spp) transmitidas por insetos (Diaphorina citri), é a doença mais destrutiva dos citros e muitos têm sido os esforços visando reduzir sua disseminação nos pomares, porém, nem sempre bem-sucedidos. Somente no cinturão citrícola paulista mais de 45 milhões de plantas já foram erradicadas por causa do HLB. O objetivo deste trabalho foi investigar diferentes aspectos associados ao patossistema HLB, visando trazer informações que ajudem na contenção da doença. Foram estudados: 1) hospedeiros alternativos do inseto vetor e do patógeno; 2) ontogenia do broto vegetativo de citros e seu potencial em multiplicar D. citri; 3) requerimentos térmicos para o desenvolvimento do broto; e 4) influência do porta-enxerto na biologia de D. citri. No primeiro capítulo é apresentada revisão de literatura sobre os aspectos mais relevantes da citricultura e do patossistema em estudo e, nos demais, os resultados das pesquisas. No segundo é apresentada a importância Swinglea glutinosa (rutácea muito comum em certas regiões citrícolas) como fonte de Ca. Liberibacter asiaticus e criadouro de D. citri. A bactéria do HLB multiplicou na planta, porém atingiu populações consideravelmente menores do que em laranjeira ‘Valência’. Apresenta, portanto, baixo potencial como fonte de inóculo para os citros. Por outro lado, D. citri reproduziu abundantemente em S. glutinosa, tanto quanto nas principais variedades de laranjeiras doces e limoeiros do grupo ‘Siciliano’ cultivados no Brasil. No terceiro capítulo são apresentados detalhes do desenvolvimento do broto em laranjeira ‘Valência’ e como os diferentes estádios influenciam o potencial biótico de D. citri. O inseto completou seu ciclo de vida em todos os estádios, mas em diferentes intensidades, sendo maiores nos estádios iniciais. Com os dados criou-se um índice de favorabilidade à reprodução do inseto, que leva em consideração o peso relativo de cada estádio do broto na biologia do inseto. No quarto capítulo é apresentado o impacto da temperatura do ar sobre o broto, o que permitiu determinar os graus-dia necessários ao seu desenvolvimento (GDD) e, com base no GDD, estabelecer um modelo geral inovador de previsão de pulverizações. No quinto capítulo é demonstrado que o porta-enxerto (limoeiro Cravo, tangerineira Sunki e citrumeleiro Swingle), por mecanismos de antibiose e/ou antixenose, afetam D. citri. Mas esses fenômenos ocorrem somente na fase de seedlings, e nas copas neles enxertadas somente enquanto a planta é jovem (muda). Em plantas adultas, de maior porte, tais fenômenos não foram detectados. Podem ter sido mascarados por influência da variedade copa (laranjeira).
Huanglongbing (HLB), associated with insect-borne phloem bacteria (Candidatus Liberibacter spp), is the most destructive disease of citrus and many efforts have been made to reduce its spread in orchards, but not always well-succeeded. Only in the citrus belt of São Paulo state (Brazil), more than 45 million plants have already been eradicated because of HLB. The objective of this work was to investigate different aspects associated to the HLB pathosystem, aiming to bring information that helps in the management of the disease. We studied: 1) alternative vector insect and pathogen hosts; 2) ontogeny of the citrus vegetative shoot and its potential to multiply D. citri; 3) thermal requirements for shoot development; and 4) influence of the rootstock on the biology of D. citri. In the first chapter, a literature review on the most relevant aspects of citriculture and pathosystem in study is presented and, in the others, the results of the experiments. In the second one the importance of Swinglea glutinosa (a Rutaceae very common in certain citrus regions) as a source of Ca. Liberibacter asiaticus and host for D. citri is presented. The HLB bacteria multiplied in the plant, but reached populations considerably smaller than in 'Valencia' sweet orange. Therefore, it presents low potential as a source of inoculum for citrus. On the other hand, D. citri reproduced abundantly in S. glutinosa, as well as in the main sweet orange and lemon varieties of the 'Sicilian' group cultivated in Brazil. In the third chapter, it is presented details of the development of the 'Valencia' orange new shoot and how the different stages influence the biotic potential of D. citri. The insect completed its life cycle at all stages of new shoots, but at different intensities, being larger in the early stages. With the data, an insect reproduction index was created, which takes into account the relative weight of each shoot stage in the insect biology. In the fourth chapter, it is presented the impact of the air temperature on the shoot, which allowed to determine the degree-days required for its development (GDD) and, based on the GDD, to establish an innovative general model of spray forecasting. In the fifth chapter it is demonstrated that the rootstock (‘Rangpur’ lime, ‘Sunki’ mandarin and ‘Swingle’ citrumelo), by mechanisms of antibiosis and / or antixenosis, affect D. citri. But these phenomena occur only in the stage of seedlings, and in the scions grafted on them only while the plant is young (nursery tree). In larger adult plants, such phenomena were not detected. They may have been masked by the influence of the scion (orange) variety.
Huanglongbing (HLB), associated with insect-borne phloem bacteria (Candidatus Liberibacter spp), is the most destructive disease of citrus and many efforts have been made to reduce its spread in orchards, but not always well-succeeded. Only in the citrus belt of São Paulo state (Brazil), more than 45 million plants have already been eradicated because of HLB. The objective of this work was to investigate different aspects associated to the HLB pathosystem, aiming to bring information that helps in the management of the disease. We studied: 1) alternative vector insect and pathogen hosts; 2) ontogeny of the citrus vegetative shoot and its potential to multiply D. citri; 3) thermal requirements for shoot development; and 4) influence of the rootstock on the biology of D. citri. In the first chapter, a literature review on the most relevant aspects of citriculture and pathosystem in study is presented and, in the others, the results of the experiments. In the second one the importance of Swinglea glutinosa (a Rutaceae very common in certain citrus regions) as a source of Ca. Liberibacter asiaticus and host for D. citri is presented. The HLB bacteria multiplied in the plant, but reached populations considerably smaller than in 'Valencia' sweet orange. Therefore, it presents low potential as a source of inoculum for citrus. On the other hand, D. citri reproduced abundantly in S. glutinosa, as well as in the main sweet orange and lemon varieties of the 'Sicilian' group cultivated in Brazil. In the third chapter, it is presented details of the development of the 'Valencia' orange new shoot and how the different stages influence the biotic potential of D. citri. The insect completed its life cycle at all stages of new shoots, but at different intensities, being larger in the early stages. With the data, an insect reproduction index was created, which takes into account the relative weight of each shoot stage in the insect biology. In the fourth chapter, it is presented the impact of the air temperature on the shoot, which allowed to determine the degree-days required for its development (GDD) and, based on the GDD, to establish an innovative general model of spray forecasting. In the fifth chapter it is demonstrated that the rootstock (‘Rangpur’ lime, ‘Sunki’ mandarin and ‘Swingle’ citrumelo), by mechanisms of antibiosis and / or antixenosis, affect D. citri. But these phenomena occur only in the stage of seedlings, and in the scions grafted on them only while the plant is young (nursery tree). In larger adult plants, such phenomena were not detected. They may have been masked by the influence of the scion (orange) variety.
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Palavras-chave
Citrus sinensis, Murta, Hospedeiros alternativos, qPCR, Swinglea glutinosa, Orange jasmine, Alternative host