STUDY ON THE ELIMINAITON OF CITRUS HUANGLUNGBIN PATHOGEN BY SHOOT-TIP GRAFTING IN VITRO

A study on the elimfnation of citrus Huanglungbin pathogen by shoot tip grafting (STG) in vitro was made from 1983 to 1986. The result showed that 3 budlings by STG were obtained from 85 Huanglungbin takan seedlings. The STG budlings and original diseased Pankan seedlings (control) were indexed for the presence of Huanglungbin pathogen respectively by the methods of biological test and electron microscope examination. The indicated Ponkan seedlings inoculated with the buds from STG budlings did not show any Huanglungbin symptoms, and in the sieve cells of leaf vein of indicated seedlings no Huanglungbin pathogen was discovered under electron microscops. On the other hand, the typical symptoms appeared on the indicated Ponkan seedlings inoculated with the buds of control plant after 5-9 months and many typical pathogens (rickettsia-like or bacteria-like organisms) were found in their sieve cells of leaf vein under electron microscope. These results showed that the Huanglungbin pathogen could be eliminated by STG.