Detection of the Asian and African liberobacter species caused greening disease of citrus with PCR

Greening is a severe and wide spread disease of citrus in two main citrus growing areas of the world, Asia and Africa. Study of the greening pathogen became more difficult since this organism has not been cultured in vitro, and the detection of the pathogen can be done only by electron microscopy. It had recenty been characterized from the sequence of its 16 S ribosomal DNA. The bacterium is a new candidates genus of liberobacter, that has been recogniied as Liberobacter asiaticum and Liberobacter africanum. This paper reports a PCR method to detect the two Liberobacter species in citrus trees by amplification of a 1160 by fragment of their 16 S rDN A. Distinction between the two species has also been achieved by X ba I restriction analysis on 4% agarose of the amplicons. The results showed that Liberobacter africanum bands appeared as 3 fragments: 520 bp, 506 by and 130 by while the Liberobacter asiaticum band appeared as 640 by and 520 bp. Keywords: Citrus greening - Liberobacter africanum - - Liberobacter asiaticum � 16 S r DNA � PCR deterction