Eradication of Xanthomonas cucurbitae in pumpkin seed by hot-water treatment

This study was conducted to develop an effective seed treatment to eradicate Xanthomonas cucurbitae, the causal agent of cucurbit bacterial spot, in pumpkin seeds. Naturally-infected seeds with X. cucurbitae were used in this investigation. Infected and uninfected seeds of 'Howden' pumpkin were collected from symptomatic and asymptomatic fruits, respectively, in the research plots at the Research Farm of the University of Illinois in Champaign, Illinois, United States. Samples of the collected seeds were tested for the presence of X. cucurbitae. Infected and uninfected seeds were treated in water at 49, 50, 51, 52, 53, 54, 55, and 56°C for 5, 10, 15, 20, 25, and 30 min at each temperature. Treated seeds were evaluated in the laboratory and greenhouse for germination, seedling vigor, and presence of X. cucurbitae in the seeds. Treatments of seeds in water with temperatures below 55°C did not eradicate X. cucurbitae in the seeds and treatments at 56°C adversely affected seed germination and seedling vigor. Hot-water treatment at 55°C for 15 min eradicated X. cucurbitae in the seeds without any significant adverse effect on either seed germination or seedling vigor.