Southern blotting hybridization of undigested S. citri GII3-3X total DNA. Plasmids were separated from chromosomal DNA by long electrophoresis on 0.5% agarose gels (A, B, C) or classical 1% agarose gel electrophoresis (D) and stained with ethidium bromide (A, D track 1). Probes used for Southern blotting hybridization (C and D track A) are indicated above tracks. U, pSci1-6 universal probe; A, pSciA specific probe; M, DNA ladder. Membrane strips of a preparative gel were used for Fig. 3C hybridizations.