ALTERNATIVE IRRIGATION WATER SALINITY AND THE FATE OF PATHOGENIC BACTERIA

The goal of this project is to provide: 1) knowledge necessary to determine whether alternative irrigation sources increase the persistence of FIB and foodborne pathogens, and risk of contamination; and 2) informed recommendations for alternative and salinizing irrigation waters, which will ultimately improve management of alternative water sources in vegetable production. The research objectiveis to determine how salinity and salt type in alternative irrigation water alters the fate of FIB and foodborne pathogens in food production. The central hypothesis is that moderate salinity levels (0.35 - 1.0 dS m-1) increase the persistence and concentration of FIB and foodborne pathogens in water, soil, and plant fruits and leaves, but the magnitude of the effects depends on salt type. We will achieve themajor goals via the following specific objectives:Specific Objective 1: Survey salinity, salt type, and FIB concentrations of alternative and traditional irrigation water sources used in the Commonwealth of Virginia. Specific hypothesis 1: Compared to traditional sources, alternative irrigation water will have a higher average salinity and greater concentrations of FIB. Approach 1: We will collect irrigation water samples from sources in Virginia, measure the in-situ concentrations of FIB and the water chemistry.Specific Objective 2: Experimentally determine the effects of salinity and salt type on the persistence of FIB and foodborne pathogens in water. Specific hypothesis 2: salinity, and specifically Mg2+, will increase the persistence of pathogenic bacteria and FIB in water. Approach 2: We will inoculate and measure the persistence of Salmonella, E. coli O157:H7, and FIB in water mesocosms with differing salinities and salt types. Specific Objective 3: Determine the effects of irrigation salinity and salt type on the persistence of FIB and foodborne pathogens in soil and on growing tomato and romaine lettuce plants. Specific hypothesis 3: increasing salinity alters the persistence of pathogenic bacteria in the soil, on tomato fruits and lettuce leaves. Approach 3: We will grow tomatoes and romaine lettuce in the greenhouse using irrigation water with different salinities and salt types, then measure the persistence of Salmonella, and E. coli O157:H7 in the soil and on plant fruit and leaves after inoculations.