Evaluation location: Campania, Italy
ISO 121 - Visual Examination. CONDITIONS: Growth Chamber and Green House - 12h light with 90% R.H. at either 18 or 24C in GC. 20C GH METHOD NARR: Two inoculation methods were used. Stem immersion method: Stems were taken from tubers and immersed in bacterial suspension for 30 minutes. Stems were then planted and transferred to a growth chamber. After 12 days symptoms were assessed. Stem injection method: Seven week old plants were inoculated with 5ul of bacterial suspension using a hypodermic syringe. They were then placed in a (20C) temperature controlled GH. Symptoms were recorded 15 days post-inoculation. RESULTS NARR: Correlation coefficients between the two methods were highly significant when innoculations were made both with Eca and with Ecc. Stem immersion method: Resistant = <15% of stems with symptoms, Intermediate = 16-25% of stems with symptoms, Susceptible = >26% of stems with symptoms. Stem Injection Method: 1 = no symptoms, 2-3 = brown and dry necrosis < 1cm at the inoculation site, compartmentized cancer, 4 = brown rot 2-3cm from the inoculation site, active cancer, 5= brown necrosis > 3cm. Resistant=2-4mm, Intermediate=4-6mm and >6= Susceptible diameter rots. AUTHOR EXPLANATION: Findings indicate that resistance to blackleg in the 2 species of Erwinia is controlled by the same mechanism or, that genes with pleiotropic effect control the resistance to Eca and Ecc.