Fig. 12. Infectivity of diploids carrying a single dose of B-cyclin genes. (A) Morphology of a wild-type diploid cell (inset, FBD11 cells at same magnification) and a diploid cell with a single gene dose of clb2 (UMP32). Cells were grown in CMD to exponential phase and DAPI stained. Scale bar: 10 µm. (B) Charcoal assay of diploid strains heterozygous for mating type. FBD11 is a wild-type strain, UMP21 has a single dose of the clb1 gene, and UMP32 has a single dose of the clb2 gene. (C) Disease symptoms on the leaf blades of young maize plants 14 days post inoculation with the strains indicated. Strong anthocyanin production was induced by infection with UMP32 but no tumors were apparent. (D) Hyphal development of wild-type, UMP21 and UMP32 cells inside the plant tissue. Observe that mutant UMP32 cells appeared to have fewer branches and the hyphae look wider the wild-type hyphae. Scale bars: 20 µm.