Detection of Acidovorax citrulli, the Causal Agent of Watermelon Bacterial Fruit Blotch, in Infected Seeds by SYBR Green Real-Time PCR

Acidovorax citrulli is a seed-borne bacterium that causes bacterial fruit blotch (BFB) in cucurbit crops such as watermelon and melon. Contaminated seeds for watermelon cultivation can cause severe harvest losses. In this study, seed preparation conditions were optimized to enhance SYBR green real-time polymerase chain reaction detection of low-level A. citrulli in watermelon seeds, facilitating healthy seed selection. Watermelon seeds artificially inoculated with A. citrulli were processed using different soaking duration, with or without direct grinding, and various DNA extraction kits to compare the detection levels. The highest detection efficiency was obtained when DNA was extracted with a soil kit after either 24 hr of soaking or direct seed grinding. Furthermore, the optimized method successfully detected A. citrulli in seeds collected from watermelon fruits exhibiting BFB symptoms. These results indicate that the optimized detection conditions can be used to screen seed affected by BFB in watermelon.