THE MICROBIAL LINK BETWEEN PEANUTS AND FORMALDEHYDE

Soil disinfection is one of the most important methods to control soil-borne diseases. Formalin is commonly used as a pretreatment for potatoes, carrots, peanuts and other crops in Israel. It is applied in concentrations of 0.25-0.4% to soil a few weeks prior to planting. The active ingredient in formalin is formaldehyde (FA) which reacts readily with amines, sulphides and purines thereby causing damage to DNA and proteins in microorganisms and mammalian cells. In recent years, there have been numerous cases, in which repeated disinfection by formalin of potato and peanut fields in the south of Israel, has resulted in reduced effectiveness of disease control. This in turn caused great financial losses to the settlements and kibbutzim in the western Negev region. Work done at the Technion, has shown that the reduced effectiveness of formalin is caused due to the enrichment of soils by FA-degrading microorganisms which enabled accelerated removal of the fumigant. Several FA-degrading bacteria and fungi were isolated from these soils and identified. An analytical method was developed to determine which fields contain FA-degrading microorganisms as a tool for decision making to the farmers. Furthermore, several alternative treatments for soil disinfection were investigated.