| Summary: | 碩士 === 國立中興大學 === 植物病理學系所 === 104 === Bacterial spot disease is a worldwide-distributed plant disease on solanaceous plants and reduces plant production. Xanthomonas perforans, one of the pathogenic bacteria causes the bacterial spot disease on tomato in Taiwan. The SAn-03 strain, isolated from agricultural soil, was confirmed to have inhibitory ability against X. perforans using confrontation assays. According to the fatty acid profiles and similarity analysis of 16S rDNA and rpoB gene sequences, the SAn-03 strain was identified as Paenibacillus sp. Imaging mass spectrometry (IMS) analysis was employed to investigate the candidate antagonistic compounds, revealed that the candidate substances secreted by SAn-03 in the spectra of 500-600, 800-950, and 1,000-1,100 mass to charge ratio (m/z) might participate in antagonizing X. perforans. Moreover, to elucidate the effects on plant growth upon the inoculation of SAn-03 alone or together with X. perforans, tomato seeds were sown in the soil mixed with SAn-03, the result indicated that germination of seeds and vegetative growth of tomato seedlings are similar to the results performed by water control. Co-inoculation with SAn-03 and X. perforans on tomato by leaf spraying method, exhibited mild symptoms of bacterial spot disease, while the pre-treatment of cell suspension and the diluted culture broth of SAn-03 using leaf spraying method reduced the disease severity of bacterial spot elicited by X. perforans. On the other hand, the weekly drenching inoculation of cell suspension of SAn-03 for 3 weeks prior to the inoculation of X. perforans could increase the length and weight of stem and root of tomato. Moreover, the pre-treatment of cell suspension and the diluted culture filtrate of SAn-03 by drenching method could reduce the disease severity of bacterial spot disease. Altogether, this study revealed that the SAn-03 strain is potential to be a biocontrol agent for controlling bacterial spot diseases on tomato.
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