Arranjos de semeadura e acão da temperatura na resposta de plantas de soja ao ataque de Euschistus heros (Fabricius) (Hemiptera: Pentatomidae) e Chrysodeixis includens (Walker) (Lepidoptera: Noctuidae)
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Data
2017-05-09
Autores
Carvalho, Marina Mouzinho [UNESP]
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Universidade Estadual Paulista (Unesp)
Resumo
As plantas, por estarem constantemente expostas a diversos tipos de estresses, podem ser influenciadas pelo meio onde são cultivadas, resultando em alterações no desenvolvimento e metabolismo, e que, consequentemente, poderão influenciar em mudanças nas interações insetos-praga. Neste sentido, objetivou-se com esse estudo, avaliar as relações entre plantas de soja submetidas a estresses causados por arranjos de semeadura e aumento de temperatura, e as consequência desses fatores na interação insetos-praga que ocorrem na cultura. Para isso foram realizados dois experimentos. No primeiro experimento foram estudados, durante dois anos agrícolas consecutivos, os arranjos de semeadura: convencional 40 cm, reduzido 20 cm, fileira dupla 20 × 40 cm, e fileira dupla 20 × 60 cm; e diferentes populações de plantas: 320.000, 427.000 e 537.000 plantas ha-1. Foram avaliados nesse experimento a ocorrência de percevejos-praga durante todo o ciclo da cultura, os danos causados por percevejos/grão, três enzimas oxidativas e a produtividade. No segundo ensaio foi avaliado, em plantas de soja Bt e não Bt, o efeito de diferentes temperaturas nos parâmetros fisiológicos, na expressão do gene da proteína catalase e nos danos causados por Chrysodeixis includens (Walker, [1858]) (Lepidoptera: Noctuidae: Plusiinae). Em ambos experimentos foi verificado a influência do estresse nas plantas de soja por fatores bióticos e abióticos, com alteração nos parâmetros fisiológicos e na atividade das enzimas. No primeiro experimento durante o primeiro ano agrícola as plantas em arranjos de semeadura fileira dupla 20 × 40 e 20 × 60 tiveram a menor expressão das enzimas oxidativas inicialmente, pois estavam menos estressadas devido ao maior espaçamento entre linhas, porém, com o aumento dos percevejos nesses arranjos houve também o aumento da atividade das enzimas resultante do estresse ocasionado pelo ataque desses insetos. No segundo ano agrícola não houve diferença estatística na população de percevejos. Em relação a produtividade não houve diferença estatística no primeiro ano agrícola, e no segundo ano foram observados maiores médias nos tratamentos com arranjo de semeadura convencional e reduzido. No segundo experimento, mesmo em altas temperaturas as plantas Bt mantiveram eficiência de controle de C. includens, pois foram menos danificadas que as plantas não Bt, como foi observado nas avaliações de desfolha, área foliar e peso seco. O gene da enzima catalase no tratamento controle foi mais ativo na soja não Bt, porém nos demais tratamentos, com maiores temperaturas, foram observados maior expressão do gene em plantas Bt.
Plants, because they are constantly exposed to different types of stresses, can be influenced by the environment where they grow, resulting in changes in development and metabolism, and, consequently, may influence changes in insect-pest interactions. Thus, the purpose of this study was to evaluate the relationships between soybean plants submitted to stresses caused by planting arrangements and temperature increase, and the consequences of these factors on the insect-pest interaction that occur in the crop. For that two experiments were performed. In the first experiment, during two consecutive agricultural years were studied planting arrangements: conventional 40 cm, reduced 20 cm, double row 20 × 40 cm, and double row 20 × 60 cm; And different plant populations: 320,000, 427,000 and 537,000 ha-1 plants. In this experiment was evaluated the occurrence stink bugs during the whole crop cycle, the damage caused by stink bugs/ grain, three oxidative enzymes and productivity. In the second experiment was evaluated, on Bt and non-Bt soybean plants, the effect of different temperatures on physiological parameters, protein catalase gene expression and damage caused by Chrysodeixis includens (Walker, [1858]) (Lepidoptera: Noctuidae: Plusiinae). In both experiments, the influence of stress on soybean plants was verified by biotic and abiotic factors, with changes in physiological parameters and enzyme activity. In the first experiment during the first agricultural year the plants in 20 × 40 and 20 × 60 double rows seeding had the lowest expression of the oxidative enzymes initially, since they were less stressed due to the greater spacing between rows, but with the increase of the stink bugs in these arrangements there was also an increase in the activity of the enzymes resulting from the stress caused by the attack of these insects. In the second agricultural year there was no statistical difference in the stink bug population. About the productivity, there was no statistical difference in the first agricultural year, and in the second year were observed higher averages in the treatments with conventional and reduced planting arrangement. In the second experiment, even at high temperatures Bt plants kept the control efficiency of C. includens, as they were less damaged than non-Bt plants, as observed in the evaluations of defoliation, leaf area and dry weight. The gene of the catalase enzyme in the control treatment was more active in non-Bt soybean, but in the other treatments, with higher temperatures, higher gene expression was observed in Bt plants.
Plants, because they are constantly exposed to different types of stresses, can be influenced by the environment where they grow, resulting in changes in development and metabolism, and, consequently, may influence changes in insect-pest interactions. Thus, the purpose of this study was to evaluate the relationships between soybean plants submitted to stresses caused by planting arrangements and temperature increase, and the consequences of these factors on the insect-pest interaction that occur in the crop. For that two experiments were performed. In the first experiment, during two consecutive agricultural years were studied planting arrangements: conventional 40 cm, reduced 20 cm, double row 20 × 40 cm, and double row 20 × 60 cm; And different plant populations: 320,000, 427,000 and 537,000 ha-1 plants. In this experiment was evaluated the occurrence stink bugs during the whole crop cycle, the damage caused by stink bugs/ grain, three oxidative enzymes and productivity. In the second experiment was evaluated, on Bt and non-Bt soybean plants, the effect of different temperatures on physiological parameters, protein catalase gene expression and damage caused by Chrysodeixis includens (Walker, [1858]) (Lepidoptera: Noctuidae: Plusiinae). In both experiments, the influence of stress on soybean plants was verified by biotic and abiotic factors, with changes in physiological parameters and enzyme activity. In the first experiment during the first agricultural year the plants in 20 × 40 and 20 × 60 double rows seeding had the lowest expression of the oxidative enzymes initially, since they were less stressed due to the greater spacing between rows, but with the increase of the stink bugs in these arrangements there was also an increase in the activity of the enzymes resulting from the stress caused by the attack of these insects. In the second agricultural year there was no statistical difference in the stink bug population. About the productivity, there was no statistical difference in the first agricultural year, and in the second year were observed higher averages in the treatments with conventional and reduced planting arrangement. In the second experiment, even at high temperatures Bt plants kept the control efficiency of C. includens, as they were less damaged than non-Bt plants, as observed in the evaluations of defoliation, leaf area and dry weight. The gene of the catalase enzyme in the control treatment was more active in non-Bt soybean, but in the other treatments, with higher temperatures, higher gene expression was observed in Bt plants.
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Palavras-chave
Glycine max, Fotossíntese, Estresse oxidativo, Bacillus thuringiensis