Resistência ao sugarcane yellow leaf virus e ao afídeo vetor Melanaphis sacchari em cultivares de cana-de-açúcar e suas interações
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Data
2022-02-17
Autores
Bertasello, Luiz Eduardo Tilhaqui
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Universidade Estadual Paulista (Unesp)
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RESUMO - O amarelecimento foliar da cana-de-açúcar, causado pelo sugarcane yellow leaf virus (ScYLV) e transmitido pelo afídeo Melanaphis sacchari, é uma das doenças mais importantes dessa cultura, provocando danos às plantas e perdas econômicas. A principal forma de controle da doença é o uso de cultivares resistentes, no entanto, para adoção de estratégias de controle mais eficientes é necessário um melhor conhecimento sobre as interações do patossistema planta-vírus-vetor. O objetivo da pesquisa foi compreender melhor as interações entre o ScYLV, cultivares de cana-de-açúcar e o afídeo vetor M. sacchari bem como avaliar e caracterizar oito cultivares de cana-de-açúcar visando identificar potenciais fontes de resistência. Os experimentos de fenotipagem em campo e a quantificação viral por RT-qPCR foram conduzidos no Centro de Cana do Instituto Agronômico - IAC em Ribeirão Preto/SP, e os experimentos de comportamento alimentar por meio da técnica de EPG, preferência e desempenho biológico foram realizados no Departamento de Entomologia e Acarologia da ESALQ-USP em Piracicaba/SP. Foram avaliados a severidade dos sintomas foliares da doença em campo, os mecanismos de resistência ao inseto por desempenho biológico, preferência e comportamento alimentar, e quantificação da concentração viral por RT-qPCR, em diferentes estádios fenológicos das plantas. Destaca-se a cultivar IACBIO-266, a única caracterizada como resistente, sem presença de sintomas em campo e com título viral em níveis não detectáveis ao decorrer do tempo. As cultivares SP71-6163 e IACSP01-3127, com 12 meses após o plantio, apresentaram maior aumento do título viral em 15,4 e 23,7 vezes, respectivamente, em comparação com 0 meses após o plantio. De maneira geral, durante os registros de EPG, na cultivar IACSP96-7569 os insetos apresentaram dificuldades mecânicas durante a penetração estiletar no processo de alimentação, com atividades floemáticas mais curtas, principalmente na fase de ingestão, portando a cultivar foi considerada a mais resistente ao M. sacchari frente as outras cultivares testadas. A infecção viral apresentou resultados significativos quanto ao desempenho biológico dos insetos, demonstrando variação entre os parâmetros observados, destacando-se as cultivares IACBIO-266 e IACSP95-5000. A correlação entre os resultados observados em todos os experimentos possibilitou caracterizar as cultivares de cana quanto aos padrões de suscetibilidade e resistência ao ScYLV, assim como ao inseto vetor. Inferimos que o conjunto de fatores envolvidos na infecção pelo ScYLV, nas diferentes cultivares de cana-de-açúcar, podem induzir alterações fisiológicas na planta hospedeira, influenciando o desempenho e comportamento do inseto vetor, podendo favorecer ou dificultar a transmissão viral.
ABSTRACT - Sugarcane yellow leaf disease, caused by sugarcane yellow leaf virus (ScYLV) and transmitted by the aphid Melanaphis sacchari, is one of the most important diseases of this crop, causing damage to plants and high yield losses. The control of this disease is mainly done by deploying cultivar genetic resistance. However, to achieve high efficient control an extensive knowledge of the plant-virus-vector interactions is required. The objective of the research was to better understand the interactions between ScYLV, sugarcane genotypes and the aphid vector M. sacchari, by evaluating and characterizing eight sugarcane cultivars aiming to identify potential sources of resistance. The phenotyping assays and the viral quantification by RT-qPCR were carried out at the Agronomic Institute Sugarcane Research Centre - IAC in Ribeirão Preto/SP, while the virus-vector interactions assay at the Department of Entomology and Acarology of ESALQ-USP, in Piracicaba/SP. The severity of virus infection symptoms, the insect biological performance, preference, feeding behavior via EPG and the quantification of viral concentration by RT-qPCR were assayed at different plant phenological stages. The cultivar IACBIO-266 stands out as the only one characterized as virus resistant, free from symptoms in the field and the low viral titre reaching levels no longer detectable over time. The cultivars SP71-6163 and IACSP01-3127 showed, at 12 months after planting the highest increases in virus titer by 15.4 and 23.7 folds, respectively. ScYLV was detected in all sugarcane cultivars, with viral titre varying over sampling time. In general, during the EPG records in the cultivar IACSP96-7569 the insects showed mechanical difficulties for feeding with a shorter phloem feeding time, mainly in the ingestion phase, therefore it was considered the most resistant to M. sacchari. The viral infection significantly affected the biological performance of insects in the cultivars, which varied between the parameters observed, mainly on the cultivars IACBIO-266 and IACSP95-5000. The correlation among all the parameters allowed the classification of cultivars in different patterns of susceptibility and resistance to ScYLV and to the vector. We also inferred that the set of factors involved in ScYLV infection in each sugarcane cultivar can induce physiological changes in the host plant, affecting the performance and feeding habits of the insect vector, which may favor or hinder viral transmission.
ABSTRACT - Sugarcane yellow leaf disease, caused by sugarcane yellow leaf virus (ScYLV) and transmitted by the aphid Melanaphis sacchari, is one of the most important diseases of this crop, causing damage to plants and high yield losses. The control of this disease is mainly done by deploying cultivar genetic resistance. However, to achieve high efficient control an extensive knowledge of the plant-virus-vector interactions is required. The objective of the research was to better understand the interactions between ScYLV, sugarcane genotypes and the aphid vector M. sacchari, by evaluating and characterizing eight sugarcane cultivars aiming to identify potential sources of resistance. The phenotyping assays and the viral quantification by RT-qPCR were carried out at the Agronomic Institute Sugarcane Research Centre - IAC in Ribeirão Preto/SP, while the virus-vector interactions assay at the Department of Entomology and Acarology of ESALQ-USP, in Piracicaba/SP. The severity of virus infection symptoms, the insect biological performance, preference, feeding behavior via EPG and the quantification of viral concentration by RT-qPCR were assayed at different plant phenological stages. The cultivar IACBIO-266 stands out as the only one characterized as virus resistant, free from symptoms in the field and the low viral titre reaching levels no longer detectable over time. The cultivars SP71-6163 and IACSP01-3127 showed, at 12 months after planting the highest increases in virus titer by 15.4 and 23.7 folds, respectively. ScYLV was detected in all sugarcane cultivars, with viral titre varying over sampling time. In general, during the EPG records in the cultivar IACSP96-7569 the insects showed mechanical difficulties for feeding with a shorter phloem feeding time, mainly in the ingestion phase, therefore it was considered the most resistant to M. sacchari. The viral infection significantly affected the biological performance of insects in the cultivars, which varied between the parameters observed, mainly on the cultivars IACBIO-266 and IACSP95-5000. The correlation among all the parameters allowed the classification of cultivars in different patterns of susceptibility and resistance to ScYLV and to the vector. We also inferred that the set of factors involved in ScYLV infection in each sugarcane cultivar can induce physiological changes in the host plant, affecting the performance and feeding habits of the insect vector, which may favor or hinder viral transmission.
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Palavras-chave
Cana-de-açúcar, Sugarcane, Cultivares