Fig 1.
Schematic representation of the sexual and asexual life cycle of cereal rust fungi exemplified by the yellow rust fungus, Puccinia striiformis f. sp. tritici, infecting wheat and the sexual host, common barberry.
(A) Telia containing two-celled teliospores are formed on the senescing wheat host. Initially, each cell contains 2 haploid (n) nuclei which then fuses to form a diploid (2n) nucleus in each cell after karyogamy. (B) Germinating teliospores bearing basidia with haploid (n) basidiospores of different mating types are formed after meiotic divisions. Germinated basidiospores may infect the sexual host. (C) Pycnia bearing haploid (n) pycniospores and receptive hyphae are formed on the adaxial side of the barberry leaf after basidiospore infection. Plasmogamy occurs when pycniospores fuse with receptive hyphae of different pycnia having different mating types. (D) Subsequently, aecia containing dikaryotic (n+n) aeciospores are formed on the abaxial side of the leaf which may infect the cereal host. (E) Uredinia containing dikaryotic (n+n) urediniospores are reproduced asexually in the cereal host, which may result in polycyclic infections within the same growing season (figure modified from [16,17]).