Studies on the role of indole-3-acetic acid and cytokinins in the formation of knots on olive and oleander plants by Pseudomonas syringae pv. savastanoi.
AbstractWild type olive and oleander strs. of the pathogen produced both IAA and cytokinins in culture but the amount varied between strs. Their α-methyltryptophan resistant mutants produced little or no IAA but about the same amount of cytokinins as their parent strains.
All wild type strs. induced knots on olive whereas only the wild type strs. from oleander were pathogenic on oleander. The size of the knots on olive and the time necessary for their development varied between strs. The olive str. mutants and the mutant from the oleander str. PBa 219 did not usually induce symptoms on either host, but mutants derived from oleander strs. ITM519 and NCPPB640 caused atypical knots on olive. Mutants from the oleander strs. induced necrotic symtpoms only on oleander. The results indicate that the amount of IAA produced determines the length of the incubation period, whereas the amount of cytokinin produced determines the size of the knot.
All the wild type olive strs. and their mutants exhibited the same plasmid profile whereas the mutants derived from the oleander strs. lacked one plasmid. This suggests that the oleander strs. do not carry the genetic determinants for cytokinin production on the plasmid which encodes for IAA production.