Fosfito de potássio no controle de Sclerotinia sclerotiorum e na germinação de sementes de soja

Abstract

Soybean is an important crop for the economy of Brazil. However, soybeans producers have losses up to 15% in the harvest due to the occurrence of diseases, and a major disease is the white-mold, which the etiologic agent is Sclerotinia sclerotiorum. Among the pathogen control alternative is the use of phosphite based products. The aim of this study was to evaluate the effect of potassium phosphite on soybean seed germination and fungal incidence in soybean seeds and mycelial growth of S. sclerotiorum in vitro. Two experiments were conducted, and both used the completely randomized design. In the in vitro were tested doses 0, 2, 4, 6 and 8 mLL-¹ of two sources of potassium phosphite (Yantra® and Reforce®). For this, It has a peaked S. sclerotiorum mycelial discs in each of the petri dishes containing different concentrations of potassium phosphite on PDA culture medium. Then, the dishes were stored in BOD chambers with 25 ° C and photoperiod of 12 hours. With daily evaluations performed to measure the colony diameter until the witness reached the edge of the petri dish. Germination and health of soybean seeds, Seeds of the cultivar Syngenta 1163 RR were treated with potassium phosphite with or without the commercial fungicide Maxim® (Control, Yantra ® 200µL, Reforce® 200µL, Maxim® 125 µL, Maxim®+Yantra® 125 µL +200µL e Maxim®+Reforce® 125 µL +200µL). After the treatment, the seeds were placed on moistened germitest paper and incubated in BOD and incubated for seven days. The seed germination and incidence of fungi was evaluated. Therefore both sources of potassium phosphite obtained a similar reduction in mycelial growth curve, where the optimum doses were 6,6 and 5,8 mL.L-¹, respectively for Yantra® and Reforce®. It was observed that the fungicidal treatments where Maxim® was applied alone or in combination with phosphites decreased the fungal incidence in the seeds. Furthermore, phosphites did not affect the germination of soybean seeds and showed no signs of phytotoxicity.