Panama Disease: An Old Nemesis Rears its Ugly Head - Part 2. The Cavendish Era and Beyond

Fig. 11. Vegetative compatibility in FOC has been assessed with nitrate-nonutilizing, nit, mutants. (A) Wildtype isolates are cultured on a chlorate containing medium on which mutant sectors eventually form (lower righthand corner). (B) Mutant sectors that develop usually grow diffusely on a medium that contains nitrate as the sole source of N. These nit mutants are phenotyped for utilization of different nitrogen sources to determine the portion of the nitrate utilization pathway that has been affected. In (C) nit mutants have been plated on a basal medium that contains either ammonium (upper left), nitrate (upper right), hypoxanthine (lower left) or nitrite (lower right). Correll et al. (6) determined that the most reliable results in complementation tests were obtained when nit1 (nitrate reductase) and NitM (molybdenum cofactor, which is under the control of several genes) mutants were paired. The mutant at the top of each of these plates is a NitM mutant since it utilizes neither nitrate nor hypoxanthine. All that remain, except that on the lower left, utilize all but nitrate and are nit1 mutants. (D) Wild-type growth at the intersection of complementary mutants, as seen in the top of this picture, indicates vegetative compatibility (photos courtesy of R. C. Ploetz).



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Panama Disease: An Old Nemesis Rears its Ugly Head - Part 2. The Cavendish Era and Beyond