The Phaseolus vulgaris varieties Bac-6, Venezuela 44, Pompadour Checà and Great Northern (GN) Tara were examined for internal infection after inoculating the seeds, seedlings and plants with Xanthomonas campestris pv. phaseoli at various sites. Inoculation of the pedicels of the flower buds and small pods resulted in transmission of the bacteria through the vascular tissue of the pod to the seeds, causing internal infection without any external symptoms on either pods or seeds. Bac-6 was resistant to seed infection and Venezuela 44 was the most susceptible, followed by Pompadour Checà and GN Tara. Planting infected seeds did not result in systemic transmission of the bacteria to the seeds. Infected leaves were probably the main source of external infection of pods, which could lead to internal and/or external seed infection. A technique for assessing internal infection of seeds was developed. |
