Inactivation of the L1 (Rep) gene in pWSRi abolishes replication. Individual leaves of spinach plants were inoculated with either pWSRi (L1+) or pWSRi L1-. DNA was extracted from inoculated leaves and adjacent leaves immediately after biolistic application (Day 0) or 8 days later and used as template for PCR using pWSRi.2236 and pWSRi.2556R primers designed to amplify viral DNA. L1- indicates template DNA from leaves treated with pWSRiL1-. L1+ indicates template DNA from leaves treated with pWSRi. The sample marked (-Leaf) indicates template DNA from an untreated leaf on the pWSRi treated plant. Neg refers to PCR reactions without template and Pos indicates PCR reactions using the pWSRi plasmid DNA as a template. MW indicates HindIII/EcoRI digested lambda DNA.