Pathogenic variation of Pectobacterium carotovorum isolates and the effects of relative humidity on the severity of bacterial stem rot in potato

• Published in: Phytopathology 2010-06, Vol.100 (6), p.S31-S31
• Main Authors: Dung, J K, Schroeder, B K, Johnson, DA
• Format: Article
• Language: English
• Subjects: Bacteria; Pectobacterium; Solanum tuberosum
• ISSN: 0031-949X

Bacterial stem rot (BSR) of potato, usually caused by Pectobacterium carotovorum (Pc), causes lesions and soft rot of aerial stems. The effects of isolate and relative humidity (RH) were examined by syringe-inoculating stems of "Umatilla Russet" potato plants with Pc cells (10 super(6) CFU) suspended in sterile distilled H sub(2)O (sdH sub(2)O). Two Pc isolates obtained from BSR lesions (O207.1 and V104.1), two Pc isolates collected from soft rot tubers (Ec101 and 1.1.2009) and a sdH sub(2)O control were used. Plants were subjected to 90-100% (high) RH or 20-30% (low) RH for 24 hr post-inoculation (p.i.) and placed in a greenhouse for evaluation. Areas under the lesion progress curve (AULPC) were calculated from lesion length measurements taken at 2, 4 and 8 days p.i. Stems and progeny tubers were sampled and plated onto CVP to detect pectolytic bacteria. Significant (P < 0.0006) effects of isolate, RH and isolate x RH interaction on AULPC values were observed. AULPC values were significantly greater with isolates O207.1, V104.1 and 1.1.2009 than with the sdH sub(2)O control at both RH treatments and were significantly greater at high RH than low RH. Isolate Ec101 was not significantly different from the sdH sub(2)O control at low RH but was significantly greater at high RH. Pectolytic bacteria were recovered from .70% of inoculated stems but were not isolated from progeny tubers. These results indicate that isolates of Pc may vary in their capacity to cause BSR lesions and RH may affect symptom severity.