Development of iodine agent sterilizer for soilless culture and its effect on the control of spinach [Spinacia oleracea] fusarium wilt

The reaction of iodine in the nutrient solution was investigated. Iodine reacted only with Fe-EDTA very slowly, and iodine in a Fe-EDTA solution decreased from 10 ppm to 1 ppm one day later. Iodine stability in nutrient solution under different pH condition was measured. Under weakly acidic condition around pH 6, iodine tended to remain stable. An iodine disinfection system for soilless culture system consisting of an iodine release resin and iodine recovery resin was assembled. The effect of the disinfection system on the growth of spinach was evaluated in NFT with two disinfection methods using Fusarium oxysporum (f. sp. spinaciae) infected nutrient solution. The first method (Two steps system); 2 ppm of iodine could be stably eluted to the nutrient solution and circulated the in whole cultivation system for disinfection and then recovered iodine from the solution. In this method, wilt disease was completely controlled. The second method (Series system); iodine eluting, disinfection and iodine recovery were concluded in a closed system. Although the solution introduced to the system was complete, but the whole cultivation system was not disinfected. It is necessary to reconsider the treatment condition. As both treatments can be combined during culture, the series system can be used usually and the two-step system should be used if symptoms of disease are found in the plants.