Virulence spectrum of Ralstonia solanacearum strains isolated from grafted and non-grafted tomato plants
Burlakoti, R. R., Chen, J.-R. 2018. Virulence spectrum of Ralstonia solanacearum strains isolated from grafted and non-grafted tomato plants. British Columbia Regional Meeting, 2017/Réunion régionale de la Colombie-Britannique, 2017, Canadian Journal of Plant Pathology, 40:1, 153-160, DOI: 10.1080/07060661.2017.1416041.
Bacterial wilt caused by Ralstonia solanacearum (Rs) is the most important tomato disease in Taiwan and other tropical countries. Grafting technique using resistant rootstock is an effective method to manage bacterial wilt. Eggplant cultivar ‘EG203‘ has been commonly used as a resistant rootstock in Taiwan. The objective of the study was to understand the impact of grafting on the virulence spectrum of Rs strains. Bacterial strains were collected from two fields from grafted plants and one field from non-grafted plants in summer 2015 in Nantou county. A total of 29 strains were isolated and identified as a Rs and their virulence levels were evaluated on three tomato genotypes and two eggplant genotypes in the greenhouse. Two previously characterized strains of Rs, Pss4 (moderately virulent) and Pss190 (highly virulent) were used as positive controls. The base of seedling stems was drenched with a bacterial suspension of each strain and disease was rated at 21 and 28 days after inoculation. All 29 strains caused high disease severity in the susceptible tomato line L390 (78–100%) and eggplant line EG048 (97–100%). All 29 strains and check strain Pss4 caused low infection on resistant tomato Hawaii7996 (0–28%) and ‘EG203’ (0–18%). However, the check strain Pss190 caused high disease severity on Hawaii7996 (61% and 91%) and moderate disease severity on ‘EG203’ (17% and 48%). We did not find much difference in the virulence of strains isolated from grafted and non-grafted tomato plants, although variability was found among the individual strains. The findings indicate that the resistant rootstock may not have much impact on the virulence of Rs strains.