Comparação entre métodos de extração de cistos de Heterodera glycines do solo

Abstract

The soybean crop is one of the most important in the world, and one of the most important in Brazil, which has been increasingly recognized as one of the world's largest producers of this grain. However, the achievement of better productive yields has been limited by the spread of diseases and the pest attacks. Within this context, the presence of phytonematodes, became increasingly important, highlighting among the species of major economic importance for soybean, the Heterodera glycines, the soybean cyst nematode (NCS). The objective of this work was to compare the methods used by the various laboratories in Brazil to extract NCS cysts from the soil. Three independent experiments were conducted in order to compare the different extraction processes used in nematology laboratories in Brazil and the effects of the methods on counting the number of NCS cysts extracted from soil samples in the Midwest conditions. In the first experiment, four variables of the modified method of Abrantes et al. (1976) were analyzed, performing sixteen treatments with four replicates each. It was organized in a 2x2x2x2 factorial scheme with a randomized block design. It was observed that the best efficiency in the extraction of the cysts occurred when the solution was sieved three times, and no statistical significance was presented for the values found for the other factors or between interactions of the studied factors. In the second experiment, the variation of the decantation time was analyzed using the Shepherd method (1970), organized in a randomized block design with five repetitions, and using five decantation periods. The largest number of cysts was recovered after 20 minutes of decantation. In the third experiment, five treatments used in nematology laboratories in Brazil were analyzed. The experiment was organized in a factorial 5x2 scheme with a randomized block design with four replicates, analyzing three variations of the modified Abrantes method (1976), the Fenwick method (1940) and the Shepherd method (1970), using extractions in dry and moist soil. Therefore, it can be concluded that the most efficient method for NCS cyst extraction was the modified Abrantes method (1976), with three sieves.