Comportamento alimentar de Bemisia tabaci biótipo B (Hemiptera: Aleyrodidae) em genótipos de soja na presença e ausência de silício
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2017-02-24
Autores
Godoy, Ana Flávia [UNESP]
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Universidade Estadual Paulista (Unesp)
Resumo
A soja, [Glycine max (L.) Merrill], é um dos cultivos mais importantes para o Brasil, com alta produtividade e intensa participação no mercado externo. Seus grãos representam importante fonte nutricional para o homem e seus derivados são usados para alimentação animal ou mesmo na fabricação de energia renovável, na forma de biodiesel. No entanto, a produção desta leguminosa pode ser comprometida pelo ataque de insetos-praga, como a mosca-branca, Bemisia tabaci (Gennadius) biótipo B (Hemiptera: Aleyrodidae). Atualmente, este inseto é apontado como importante praga para a cultura da soja, devido às crescentes infestações e dificuldade no controle. Seu manejo é feito principalmente através de aplicações sucessivas de inseticidas sintéticos, as quais favorecem à rápida seleção de indivíduos resistentes. Desta forma, torna-se importante avaliar alternativas menos agressivas, alinhadas ao manejo integrado de pragas (MIP), com destaque para o uso de cultivares resistentes e indutores de resistência, como o silício. O monitoramento da alimentação de insetos sugadores por meio da técnica de EPG (Electrical Penetration Graph) tem auxiliado na caracterização de categorias e fatores de resistência de plantas frente ao ataque de insetos. Assim, neste trabalho, avaliou-se o comportamento alimentar de B. tabaci biótipo B em genótipos resistentes e suscetíveis de soja na presença e ausência de silício, utilizando-se EPG. Na primeira etapa, foram avaliados quatro genótipos de soja portadores de diferentes categorias de resistência à mosca-branca (KS-4202, tolerância; IAC-19, antixenose; UX-2569-159, antibiose e PI-227687, suscetível). Paralelamente, caracterizou-se os tipos de tricomas presentes na superfície abaxial dos folíolos, a fim de estabelecer possíveis correlações com o comportamento alimentar da mosca-branca. Os resultados confirmaram a presença de fatores antixenóticos no genótipo IAC-19 (baixa duração de alimentação na fase floemática). A elevada densidade de tricomas no genótipo PI-227687 revelou-se como um fator antixenótico (atrasa o início das picadas de prova). KS-420 manifestou-se adequado à alimentação da mosca-branca, comportamento já esperado em materiais tolerantes. Em UX-2569-159 (antibiose previamente relatada) é provável que a resistência esteja mais relacionada à expressão de antixenose (elevado período de alimentação no floema). Na segunda etapa, avaliou-se o comportamento alimentar de B. tabaci biótipo B em dois genótipos de soja com diferentes níveis de suscetibilidade ao inseto (IAC-19, portador de antixenose e Conquista, suscetível) na presença e ausência de silício. Os resultados obtidos confirmaram a presença de fatores antixenóticos no genótipo IAC-19 e sugerem que a utilização do mineral, via aplicação foliar, acentuou os fatores de antixenose existentes neste genótipo (aumento do tempo até a primeira picada e redução no tempo de alimentação em floema). Em Conquista, o silício interferiu no tempo até a primeira picada de prova, sugerindo incremento de barreiras físicas na epiderme.
Soybean, [Glycine max (L.) Merrill], is one of the most important crops for Brazil, with high productivity and strong participation in the foreign market. Soybeans represent important nutritional source for humans and their derivatives are used in animal nutrition or even renewable energy production, as biofuel. However, production of this crop may be affected negatively by the attack of insect pests, such as the whitefly, Bemisia tabaci (Gennadius) biotype B (Hemiptera: Aleyrodidae). This insect is currently indicated as an important pest for the soybean crop, due to the increasing infestations and difficulty in control. Its management is mostly done with successive spraying of synthetic insecticides that promote rapid selection of resistant individuals. Thus, it is important to evaluate less aggressive alternatives, aligned with the integrated pest management (IPM), with emphasis on the use of resistant cultivars and resistance inducers, as silicon. Monitoring sucking insects feeding using the EPG technique (Electrical Penetration Graph) has been helping in the characterization of categories and resistance factors of plants against insect attacks. In this study, the feeding behavior of B. tabaci biotype B was assessed in resistant and susceptible genotypes of soybean in the presence and absence of silicon using EPG. In the first stage, four genotypes of soybean bearers of different categories of resistance against the whitefly were assessed (KS-4202, tolerance; IAC-19, antixenosis; UX-2569-159, antibiosis e PI-227687, susceptible). At the same time, the types of trichomes present on the abaxial surface of the leaflets were characterized, in order to establish possible correlations with the feeding behavior of the whitefly. The results confirm the presence of antixenotic factors in the genotype IAC-19 (low duration of feeding in the phloem phase). The high density of trichomes in the genotype PI-227687 was revealed as an antixenotic factor (delays the beginning of probing). KS-4202 was suitable for whitefly feeding, expected behavior in tolerant genotypes. In UX-2569-159 (antibiosis previously reported) resistance is likely more related to expression of antixenosis (high period of phloem feeding). In the second stage, the feeding behavior of B. tabaci biotype B was evaluated in two soybean genotypes with different levels of susceptibility to the insect (IAC-19, bearer of antixenosis and Conquista, susceptible) in the presence and absence of silicon. The results confirmed the presence of antixenotic factors in the genotype IAC-19 and suggest that the use of this mineral, through foliar application, accentuated the existing antixenosis factors in this genotype (increased time until probing and reduction in time of phloem feeding). Silicon interfered on the time until probing in Conquista, suggesting increment of physical barriers on the epidermis.
Soybean, [Glycine max (L.) Merrill], is one of the most important crops for Brazil, with high productivity and strong participation in the foreign market. Soybeans represent important nutritional source for humans and their derivatives are used in animal nutrition or even renewable energy production, as biofuel. However, production of this crop may be affected negatively by the attack of insect pests, such as the whitefly, Bemisia tabaci (Gennadius) biotype B (Hemiptera: Aleyrodidae). This insect is currently indicated as an important pest for the soybean crop, due to the increasing infestations and difficulty in control. Its management is mostly done with successive spraying of synthetic insecticides that promote rapid selection of resistant individuals. Thus, it is important to evaluate less aggressive alternatives, aligned with the integrated pest management (IPM), with emphasis on the use of resistant cultivars and resistance inducers, as silicon. Monitoring sucking insects feeding using the EPG technique (Electrical Penetration Graph) has been helping in the characterization of categories and resistance factors of plants against insect attacks. In this study, the feeding behavior of B. tabaci biotype B was assessed in resistant and susceptible genotypes of soybean in the presence and absence of silicon using EPG. In the first stage, four genotypes of soybean bearers of different categories of resistance against the whitefly were assessed (KS-4202, tolerance; IAC-19, antixenosis; UX-2569-159, antibiosis e PI-227687, susceptible). At the same time, the types of trichomes present on the abaxial surface of the leaflets were characterized, in order to establish possible correlations with the feeding behavior of the whitefly. The results confirm the presence of antixenotic factors in the genotype IAC-19 (low duration of feeding in the phloem phase). The high density of trichomes in the genotype PI-227687 was revealed as an antixenotic factor (delays the beginning of probing). KS-4202 was suitable for whitefly feeding, expected behavior in tolerant genotypes. In UX-2569-159 (antibiosis previously reported) resistance is likely more related to expression of antixenosis (high period of phloem feeding). In the second stage, the feeding behavior of B. tabaci biotype B was evaluated in two soybean genotypes with different levels of susceptibility to the insect (IAC-19, bearer of antixenosis and Conquista, susceptible) in the presence and absence of silicon. The results confirmed the presence of antixenotic factors in the genotype IAC-19 and suggest that the use of this mineral, through foliar application, accentuated the existing antixenosis factors in this genotype (increased time until probing and reduction in time of phloem feeding). Silicon interfered on the time until probing in Conquista, suggesting increment of physical barriers on the epidermis.
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Palavras-chave
Glycine max (L.) (Merrill), Mosca-branca, Resistência de plantas a insetos, Silício, EPG, Whitefly, Plant resistance to insects, Silicon