By cloning and sequencing specific randomly amplified polymorphic DNA (RAPD) products, we have developed pairs of PCR primers that can be used to detect Xylella fastidiosa in general, and X. fastidiosa that cause citrus variegated chlorosis (CVC) specifically. We also identified a CVC-specific region of the X. fastidiosa genome that contains a 28-nucleotide insertion, and single base changes that distinguish CVC and grape X. fastidiosa strains. When using RAPD products to develop specific PCR primers, we found it most efficient to screen for size differences among RAPD products rather than presence/absence of a specific RAPD band.

Garlic (Allium sativum L.) has a long history of obligate vegetative propagation. In this study, isozyme and morphological characters were analyzed for 110 diverse clones of garlic and the proposed progenitor species, A. longicuspis. The clones displayed 17 different electrophoretic phenotypes, which were associated with morphological traits. An isozyme-based phenetic tree was contructed to explain the possible relationships of various garlic clones and A. longicuspis. The lack of unique isozyme and morphological characters of A. longicuspis suggests an artificial species separation.