Changes of pectin content in resistant alfalfa plants after inoculation with differently virulent isolates of Corynebacterium michiganense pv. insidiosum

6 Week-old alfalfa plants resistant to bacterial vascular wilt disease were inoculated with the strongly, moderately and slightly virulent isolates of Corynebacterium michiganense pv. insidiosum (McCulloch) Dye and Kemp and also with a mixture of these three ones. On the 3rd, 7th and 14th day after inoculation the pectin contents in overground parts and roots were determined and compared with the control, i.e. uninoculated plants. The inoculation of resistant plants with the slightly virulent isolate V-8 was found to cause nearly no changes of cell wall pectin contents in the overground parts and the roots. The inoculation with the more virulent isolates CIT, VLN-3 and the mixture of all three caused a decrease of cell wall pectin content. These decreases were approximately the same.