Fig. 1. PCR amplification of nuclear DNA from 18 lines of tobacco using the N-gene specific primer pairs (a) E1 + E2 and (b) N1 + N2. Lanes 1 through 20 are: (1) 100 bp ladder, (2) Samsun, (3) Red Russian, (4) Connecticut Broadleaf, (5) K326, (6) NC 1125-2, (7) TI 1407, (8) TI 1459, (9) 1462, (10) TI 1463, (11) TI 1473, (12) TI 1492, (13) TI 1500, (14) TI 1501, (15) TI 1504, (16) Xanthi nc, (17) Xanthi NN, (18) Samsun NN, (19) Holmes Samsoun, (20) 100-bp ladder.