Two distinct segments of transferred DNA (T-DNA) were detected in tumor tissue incited by Agrobacterium rhizogenes strain A4 on Nicotiana glauca. RNA from these tumors was examined for the presence of T-DNA encoded transcripts. Six genetic loci involved in virulence and tumor morphology have been identified by transposon mutagenesis: rol A-D on the leftward T-DNA (TL-DNA) and tms1 and 2 on the rightward T-DNA (TR-DNA). On the basis of map position, the rol A-D loci are associated with transcripts of 650, 1,050, 850 and 1,250 nucleotides, respectively, while the tms loci are associated with transcripts of 2,500 and 1,600 nucleotides. An additional transcript of 1,050 nucleotides not associated with a detectable phenotype was identified on the TL-DNA. On the TR-DNA, at least four transcripts other than those associated with tms1 and 2 were identified.