Studies on the genomic organization of Magnaporthe grisea

Jose Manuel Romao, Purdue University

Abstract

The rice blast fungus Magnaporthe grisea parasitizes gramineous plants, including rice and other cultivated species. The rice-specialized group causes devastating epidemics in rice growing areas around the world. Blast is the most deleterious disease of this economically important crop and yet M. grisea is still a relatively poorly understood organism. Thus, it becomes very pressing to elucidate the mechanisms of the disease and the biology of both host plant and pathogen. The development of a genetic linkage map for M. grisea would permit the cloning of infection-specific genes based on chromosomal position, the ordering of cosmid libraries, investigations of genome rearrangements, and other studies as well. A linkage map was constructed in M. grisea based on the MGR586 middle repetitive DNA family. One MGR probe was employed to simultaneously follow the segregation of fifty-seven MGR586 sequences in crosses between polymorphic strains. An array of multi-locus linkage groups was rapidly established. The MGR586 sequences were found to be randomly distributed in the genome. This characteristic permitted further localizing on linkage groups of several markers of varied types. These included the mating-type locus, pigmentation genes, the rRNA gene cluster, and RFLP probes. Different experiments were carried out to assess the reliability of the parallel RFLP map. These included the mapping of telomeric loci, and comparisons of marker position, order, and distances in independently constructed maps. A final linkage map was produced after additional work to increase its accuracy. It includes members of two other repeated dispersed RFLP sequences found in M. grisea: MGR583 and Grasshopper. It also contains the telomeres, a pathogenicity gene, the cutinase gene, and several new RFLPs.

Degree

Ph.D.

Advisors

Hamer, Purdue University.

Subject Area

Genetics|Molecular biology|Plant pathology

COinS