Translocação de fosfito na presença de fungicidas em plantas de soja e seu efeito no controle de oídio

Abstract

Soybean is a crop that stands out for its extreme importance in national and global agricultural production, but there are several factors that affect the productivity, especially diseases. And the most used way to fight them is through chemical control. However, most diseases develop in the lowest part of the plants, which creates control difficulties because to the low percentage of product that is deposited in this region. For this reason, the use of alternative products that can increase efficiency when associated with fungicides has been widely used. Therefore, potassium phosphite represents one of these products with satisfactory results in the management of diseases. However, there are few studies related to the effects of the association between fungicides and phosphites and the translocation way them. The objective of this study was to verify, in a greenhouse, the potential of potassium phosphite in disease control, being applied alone or associated with different fungicides. It also aimed to elucidate the mode of action of this combination in different parts of the plant. For this, the first study was carried out in order to verify the possible translocation of the fungicide associated with potassium phosphite by assessing the severity of powdery mildew in different trifolios of the plant. Besides analyzing of phosphorus concentration and theoretical computational modeling to ascertain the interaction between the fungicide and phosphite molecules. In the second study, it was also evaluated the systemic activity of resistance induction in different trifolios with the application of phosphite and fungicide. Thus, the results of the first study, with tests carried out in a greenhouse, showed an efficient reduction in the severity of powdery mildew in the lower leaves when potassium phosphite was associated with the fungicide. Regarding the analysis of phosphorus concentration, it was observed that the phosphite was able to translocate via xylem and phloem and that there was an increase in the concentration in the lower leaves when it was associated with the fungicide. With the analysis of the theoretical computational results, it was possible to infer that the phosphite and fungicide molecules are capable of interacting with each other, being an advantageous attribute to carry the fungicide downwards. In the second study, carried out by means of biochemical analyzes, the results showed the systemic action of the treatments used for all evaluated enzymes, but only treatments with potassium phosphite associated with the fungicide showed a higher percentage of powdery mildew control in the lower leaves. Based all the results obtained with the present study, it can be concluded that the effective action of the association between phosphite and fungicide in the control of powdery mildew, and the results obtained in this investigation are promising as an additional tool for the control of several diseases.