Leaf and stem crown galls on perennial asters caused by Agrobacterium tumefaciens in Taiwan

Leaf, stem, and crown galls induced by Agrobacterium tumefaciens were obser ved on field grown perennial asters (Aster spp.). Plants of purple flowers were more susceptible to infection than white flowers. The occurrence range d from 25% in white flowered and 90% in purple flowered plants. Galls also occurred on leaves wounded by insect bites or mechanical shearing. Agrobact erium tumefaciens was isolated from crown and leaf galls with a selective m edium NASA. The bacterial isolate was identified as A. tumefaciens using th e Biolog GN system. Inoculation of selected A. tumefaciens strains on Kalan choe pinnata leaves resulted in gall formation 8 similar to 10 days afterwa rd. Several other A. tumefaciens strains from different gall samples also c aused gall formation 6 similar to 8 days after inoculating on the stems of tobacco, and tomato seedlings. Re-inoculating virulent strains by scissors onto healthy aster leaves also induced galls 10 to 12 days after cut-inocul ation, Biochemical tests of most Agrobacterium strains from aster galls sho wed that they belong to biovar 1.