Submitted to: Phytopathology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 1/23/2004
Publication Date: 6/1/2004
Citation: Kosman, E., Pardes, E., Szabo, L.J., Anikster, Y., Manisterski, J., Yehuda, B.P., Sharon, A. 2004. Genetic variation, distribution, and the development of virulence on lr26 in populations of the wheat leaf rust fungus puccinia triticina. Phytopathology. Interpretive Summary: Wheat leaf rust is widespread throughout the world and accounts for major losses each year. At present, the best means of control of wheat leaf rust is through the use of wheat cultivars containing leaf rust resistance genes. These genes are race specific and changes in the leaf rust population occur often and result in plant resistance breaking down. Isolates of wheat leaf rust from USA, Israel and Europe were examined usin DNA markers and ability to cause disease on 16 different wheat cultivars each containing a different leaf rust resistance gene. The results indicate that there is no significant exchange of wheat leaf rust isolates between Israel and Europe, but there is between Israel and USA. This information will be used by scientists for studies on epidemiology of wheat rust disease and wheat breeders.
Technical Abstract: Isolates of Puccinia triticina were obtained from Israel, Europe and the U.S.A. The isolates in each of the three populations were tested for virulence on a Thatcher wheat line with the Lr26 resistance gene. The diversity within and between the three major populations, and within and between the Lr26 virulent and avirulent sub-populations were determined by comparison of virulence phenotype on 16 near isogenic Thatcher lines that carry leaf rust resistance genes, and by random amplified polymorphic DNA (RAPD) markers. The diversity within the isolates from Israel was low relatively to the isolates from Europe and the USA according to the virulence phenotype and high according to the RAPD markers. The Lr26 sub-populations from the different geographical locations exhibited a similar trend. The distances between the populations from Israel and Europe were the largest, and between Europe and the USA the smallest. Cluster analysis according to RAPD markers divided the entire population into four groups. Three groups were closely associated with the geographical origin of the isolates Israel, the U.S.A. and Europe. The last group contained isolates from Israel and the U.S.A. The distance between the last group and any of the groups was significantly higher than the distances among the three other groups. The results indicate that there is no significant exchange of P. triticina isolates between Israel and Europe. There may be at least two different sources from which the fungus arrives in Israel but the precise origin is unknown. The results also indicate that the wide spread of P. triticina isolates that are virulent on Lr26 may have resulted from large scale introduction of wheat that carry the Lr26 resistance gene.