AN IMPROVED SURFACE DISINFECTION METHOD FOR SHOOT EXPLANTS FROM IRIS RHIZOMES INFECTED WITH BACTERIAL SOFT-ROT (ERWINIA-CAROTOVORA SUBSP CAROTOVORA)

The standard method (protocol 1) for disinfecting shoot explants used for initiation of plant tissue cultures failed when Iris rhizomes were infected with bacterial soft rot (Erwinia carotovora subsp. carotovor a). Two new disinfection protocols were therefore developed. They invo lved keeping stock plants without irrigation for two months prior to e xcision of explants; alcohol disinfection of the explants prior to exc ision from the rhizome; dipping of the explant in alcohol immediately after excision; soaking in 1% (v/v) sodium hypochlorite (protocol 2) o r saturated calcium hypochlorite (protocol 3); and soaking in mercuric chloride. With protocols 2 and 3 up to 90% and 62% respectively of ex plants taken from infected Iris rhizomes showing soft-rot symptoms rem ained free of detectable microorganisms in vitro.