Abstract
Strains of Pseudomonas syringae pv. mori, the causal agent of bacterial blight of mulberry, contain 2 to 4 indigenous plasmids ranging from approximately 4.5 to 70mdal and were classified into 9 groups according to their characteristic plasmid patterns. A survey of 17 isolates did not reveal apparent correlations between plasmid pattern and toxigenicity, phage sensitivity or other phenotypes tested. All strains tested accepted freely the non-conjugative plasmid RSF1010 through mobilization by naturally occurring conjugative plasmid pBPW1 of P. s. pv. tabaci BR2, but re-transferred RSF1010 into Esherichia coli at very low frequency. Thus, it seems to be indicated that they possess an indigenous fertility system which is either naturally repressed or mobilizes RSF1010 with low efficiency.
