Using random amplified polymorphic DNA to analyze the genetic relationships and variability among three species of wheat smut (Tilletia)

Covered smut or bunt of wheal, caused by Tilletia caries, T. foetida (T. laevis), and dwarf bunt, caused by T. controversa, significant pathogens of wheat. However, the molecular and genetic make-ups of these fungi have not been studied extensively. The extremely long rime required to germinate the Tilletia controversa teliospores, their thick walls and high lipid content have discouraged extensive genetic analyses of the fungi by methods such as RFLP or RAPD. We recently developed a method to extract genomic DNA from the thick-walled teliospores of Tilletia. This method was used to extract the genomic DNA from 90 smut samples. The average Tilletia DNA yield per infected wheat head was significantly different for T. controversa as compared to T. caries and T. foetida (T. laevis). RAPD reactions were performed with the 90 Tilletia individuals and 13 random primers. The resulting RAPD patterns were scored for presence or absence of specific fragments and this information was tabulated for each sample in a large data matrix. The total number of RAPD fragments per individual and per primer were calculated. A high level of genetic variability was observed between species, races, and even individuals of the same race of Tilletia. Cluster analysis of the RAPD handing patterns distinguished races of Tilletia caries, T. foetida (T. laevis), and T. controversa. No race- or species-specific markers were identified.