The ability of plant pathogenic bacteria to survive and multiply outside and inside plants, and to cause disease, is determined to a large extent by their genetic constitution. The genetic analysis of plant pathogenic bacteria currently involves the application of molecular techniques for the identification and investigation of bacterial genes that are important in all of these aspects, and will be considered first. Following sections discuss the role of specific genes and gene systems in the activity of plant pathogenic bacteria in relation to the determination of compatibility and incompatibility, disease virulence, and non-pathogenic characteristics. The final part of this chapter deals with the occurrence and role of plasmids in these bacterial cells.

Molecular genetics: identification and investigation of bacterial genes

Bacterial genes, occurring on either chromosomal or plasmid DNA, are involved in the determination of a wide range of phenotypic characteristics. In recent years new techniques of molecular biology have been particularly successful in the genetic analysis of plant pathogenic bacteria (Daniels et al., 1988), and have been described in detail in a number of recent texts (e.g. Brown, 1986; Sambrook et al., 1989). The major objectives of molecular genetics are:

1. Identification and isolation (cloning) of specific genes with defined functions.

2. […]