title: Transfer of a supernumerary chromosome between vegetatively incompatible biotypes of the fungus Colletotrichum gloeosporioides.
abstract: Two biotypes (A and B) of Colletotrichum gloeosporioides infect the tropical legumes Stylosanthes spp. in Australia. These biotypes are asexual and vegetatively incompatible. However, field isolates of biotype B carrying a supernumerary 2-Mb chromosome, thought to originate from biotype A, have been reported previously. We tested the hypothesis that the 2-Mb chromosome could be transferred from biotype A to biotype B under laboratory conditions. Selectable marker genes conferring resistance to hygromycin and phleomycin were introduced into isolates of biotypes A and B, respectively. A transformant of biotype A, with the hygromycin resistance gene integrated on the 2-Mb chromosome, was cocultivated with phleomycin-resistant transformants of biotype B. Double antibiotic-resistant colonies were obtained from conidia of these mixed cultures at a frequency of approximately 10(-7). Molecular analysis using RFLPs, RAPDs, and electrophoretic karyotypes showed that these colonies contained the 2-Mb chromosome in a biotype B genetic background. In contrast, no double antibiotic colonies developed from conidia obtained from mixed cultures of phleomycin-resistant transformants of biotype B with biotype A transformants carrying the hygromycin resistance gene integrated in chromosomes >2 Mb in size. The results demonstrated that the 2-Mb chromosome was selectively transferred from biotype A to biotype B. The horizontal transfer of specific chromosomes across vegetative incompatibility barriers may explain the origin of supernumerary chromosomes in fungi.
authors.affiliation: Cooperative Research Centre for Tropical Plant Pathology, The University of Queensland, Brisbane, Queensland 4072, Australia.
authors.forename: C
authors.initials: C
authors.lastname: He
authors.forename: A G
authors.initials: AG
authors.lastname: Rusu
authors.forename: A M
authors.initials: AM
authors.lastname: Poplawski
authors.forename: J A
authors.initials: JA
authors.lastname: Irwin
authors.forename: J M
authors.initials: JM
authors.lastname: Manners
mesh_terms: D001203:Ascomycota / Q000187:drug effects / Q000235:genetics*; D015825:Chromosomes, Fungal; D002934:Cinnamates; D004352:Drug Resistance, Microbial; D007887:Fabaceae / Q000382:microbiology; D006921:Hygromycin B / Q000031:analogs & derivatives / Q000494:pharmacology; D010946:Plants, Medicinal; D011995:Recombination, Genetic; D014170:Transformation, Genetic
chemical_list: D002934:Cinnamates; D006921:Hygromycin B; C026273:hygromycin A