Suppression of bacterial seedling rot of rice caused by Burkholderia glumae by soaking rice seeds in a suspension of converter slag fertilizer

Bacterial seedling rot of rice caused by Burkholderia glumae is a serious disease that impairs seedling development and causes seedling blight. To control this disease without depending on chemical fungicides, new strategies are required because of the emergence of fungicide-resistant strains and the environmental impacts of agriculture. In this study, we evaluated the suppressive effects of converter slag fertilizer, a steel-making by-product composed of inorganic elements, when mixed into a seed-soaking solution. Higher concentrations of powdered converter slag fertilizer in the seed-soaking solution markedly suppressed disease development. Furthermore, disease suppression occurred in a stepwise manner, with symptoms suppressed in order of severity as the fertilizer amount increased. Analysis of water-soluble elements in the seed-soaking solution suggested that multiple elements eluted from the fertilizer may be associated with the disease-suppressive environment generated during seed soaking. Notably, Ca 2+ was the most abundant water-soluble element and may contribute to disease suppression. These findings indicate that converter slag fertilizer is a promising approach for the management of bacterial seedling rot of rice.