Submitted to: Genetics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: July 30, 2001
Publication Date: N/A
Interpretive Summary: Leaf rust, is a disease of wheat caused by the fungus Puccinia triticina. This fungus is an obligate parasite, it can only live and reproduce on living wheat plants. Generally 40-50 races of the leaf rust fungus are detected in North America every year. Races of the fungus can be detected on certain lines of wheat which have different genes that condition resistance to the fungus. Differences in the DNA between collections can also be detected by using molecular biology techniques such as amplified fragment length polymorphism (AFLP). This study was undertaken to determine the genetic relationships between isolates of the fungus that are found in different parts of Canada. Sixty nine isolates of the fungus were tested for virulence and 37 different races of the fungus were detected. All of the isolates were different for AFLP pattern. Both the virulence markers and the AFLP markers placed the 69 isolates into four groups that were associated with the geographic origin of the isolates, or with certai types of races. Isolates from western Canada were generally distinct from isolates that were from eastern Canada. The average variation for both the virulence markers and AFLP markers between isolates in different groups was significantly larger than between isolates within the same group. The AFLP technique was able to distinguish between isolates that were identical for virulence characteristics. The AFLP technique will be a powerful tool to detect genetic differences among isolates of the wheat leaf rust fungus, P. triticina.
Technical Abstract: Isolates (69) of the wheat leaf rust fungus Puccinia triticina from the eastern (Ontario and Quebec), prairie (Manitoba and Saskatchewan), and Pacific (Alberta and British Columbia) regions of Canada were tested for virulence to 22 near- isogenic Thatcher wheat lines, and for amplified fragment length polymorphism (AFLP) using 10 specific amplification primer pairs. There were 37 distinct virulence phenotypes, and 69 molecular phenotypes with 164 AFLP markers. Both virulence and AFLP markers distinguished four major groups of isolates which could also be grouped according to geographic region or in broad virulence groups. The weighted average virulence distance (simple distance coefficient) within groups was 0.21, and between groups was 0.36. The weighted average AFLP variation (1- Dice coefficient) within groups was 0.24, and between groups was 0.38. Isolates from the prairies with virulence to resistance gene Lr17 were in a adistinct AFLP group while prairie isolates that were avirulent to Lr17 wer in a different group. Isolates from eastern Canada avirulent to Lr2a and virulent to Lr2c, and isolates avirulent to Lr22b were also in distinct AFLP groups. There was a 0.53 correlation between the virulence polymorphism and AFLP variation generated by all 10 selective primer pairs. AFLP variation grouped isolates in the same manner as did virulence- isozyme variation and random amplified polymorphic DNA variation.