Southern blots and PCR of total DNA from Rhs 1A1 revealing the presence of a DNA copy of the M2 dsRNA. Autoradiographs of blots of BamHI digests from M2 dsRNA clone M2–31 (A; 16 hr exposure), total DNA from the R. solani isolate Rhs 1A1 (B, lane 1; 48 hr exposure), and total DNA of Nicotiana tabacum (B, lane 2). The blots were hybridized with a 32P-labeled cDNA clone (M2–31) of M2. C shows the ethidium bromide-stained DNA size standards (lane 1), and PCR products amplified with primer combinations encompassing bases 1–1316 (lane 2), 1263–2474 (lane 3), and 2435- 3570 (lane 4) of the M2 sequence. Numbers on the left indicate size (kbp), and arrow shows the position of the recombinant plasmid carrying clone no. 31. A control PCR reaction with tobacco DNA and M2 specific primers did not give rise to any product (data not shown).