The Eleventh Regional Wheat Workshop For Eastern ... - Cimmyt

Assessment ofpathogenic variability in stripe rust - Wellings et al.
Erikkson,l. 1894. Ueber die specialisierung des parasitismus bei den getreiderostpilzen. Berlin Devt. Botantical
Ges. 12: 44-46.
Johnson, R., Stubbs, R.W., Fuchs, E. and N.H. Chamberlain. 1972. Nomenclature for physiologic races of
Puccinia striiformis infecting wheat. Transactions ofthe British Mycological Society 58: 475-480.
Latch, G.C.M. 1976. Stripe rust, Puccinia striiformis f. sp. dactylidis on Dactylis glomerata in New Zealand.
New Zealand Journal ofAgricultural Research 19: 535-536.
Manners, J.G. 1960. Puccinia striiformis Westend. var dactylidis var. nov. Transactions ofthe British
Mycological Society 43: 65-68.
Marshall, D. and RL. Sutton. 1995. Epidemiology of stripe rust, virulence ofPuccinia striiformis f. sp. hordei,
and yield loss in barley. Plant Disease 79: 732-737.
McIntosh, R.A., Wellings, C.R and R.F. Park. 1995. "Wheat Rusts; an Atlas of Resistance Genes", CSIRO
Press, 200 pp.
Pretorius, Z.A., Boshoff, W.H.P. and G.H.J. Kema. 1997. First report ofPuccinia striiformis f.sp. tritici on
wheat in South Africa. Plant Disease 81: 424.
Tollenaar, H. 1967. A comparison ofPuccinia striiformis f. sp. poae on bluegrass with P. striiformis f. sp. tritici
and f. sp. dactylidis. Phytopathology 57: 418-420. .
WeIlings, C.R and R.A. McIntosh. 1990. Puccinia striiformis f. sp. tritici in Australasia - pathogenic changes
during the first ten years. Plant Pathology 39: 316-325.
Wellings, C.R., McIntosh, R.A. and 1. Walker. 1987. Puccinia striiformis f. sp. tritici in eastern Australiapossible
means of entry and implications for plant quarantine. Plant Pathology 36: 239-241 .
Wellings, C.R, Burdon, J.J., McIntosh, R.A., Wallwork, H., Raman, H. and G.M. Murray. 2000. A new variant
of Puccinia striiformis causing stripe rust on barley and wild Hordeum species in Australia. New
Disease Report, British Society for Plant Pathology.
Questions and Answers:
Cobus Ie Roux: Are you able to distinguish between different biotypes by using the isogenic
Avocet lines in the trap nurseries?
Answer: The trap nurseries with Avocet NILs are designed to evaluate the effectiveness of
single genes. It can be expected that nurseries will be infected with one or more pathotypes.
As gene combinations in NILs become available, it will be feasible to distinguish pathotype
mixtures in nurseries. It is also anticipated that the NIL set will form the basis for a revision
of pathotype nomenclature in Pucdnia striiformis fsp. tritid.
M.A. Mahir: What is the possibility of hybridization and recombination between pathotypes
being responsible for the continuous development of new pathotypes and biotypes of YR
beside genetic mutation?
Answer: Somatic recombination between cereal rust pathotypes has been clearly documented
in Australia for wheat stem rust (P. graminis trifid) and rye stem rust (P. graminis secalis)
giving rise to hybrid stem rust pathotypes. The literature also suggests somatic recombinants
for P. striiformis. However, the evidence for P. striiformis in Australia does not support
somatic recombination at the present time.
Temam Russien: How often do you find new pathotypes of yellow rust in Australia? In
other words, what is the rate of mutation of Y r of wheat?
Answer: It is difficult to predict a precise mutation rate, since this will be a function of
population size and selection pressure. Nevertheless, it appears on average that we can expect
a new pathotype each year, although most of these pathotypes have not been signi ficant for
our commercial wheats.
140