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12 results on '"Cotterill, PJ"'

8. Pathogenic specialization of Puccinia hordei Otth. in Australia, 1966-1990

Author

Cotterill, PJ, Park, RF, and Rees, RG

Abstract

One hundred and fifty-four isolates of the leaf rust pathogen (Puccinia hordei), collected from infected barley plants in Australia between 1966 and 1990, were typed to determine virulence with respect to the resistance genes Rphl to Rph9, Rphl2 (Triumph) and several uncharacterized resistance sources. The Australian cultivar, Prior, reacted differentially to the isolates examined, and is believed to possess a gene which is also present in addition to Rph2 in Reka 1. Virulence and avirulence on Prior were designated P+ and P- respectively. Eleven distinct pathotypes (pt) were identified, with pt 243 P+ and 243 P- predominating in samples collected between 1966 and 1979. In the 1980s, pt 210 P+ was most commonly isolated from samples collected in Queensland and northern New South Wales, and although a range of different pathotypes was present in southern Australia, pt 200 P+ was most frequent in this region. Virulences to genes Rphl, Rph2, Rph4, Rph5, Rph6, Rph8, Rph9 and Rphl2 have been detected, and only Rph3 and Rph7 are likely to be of value in protecting future Australian barleys from the disease.

Published
1995
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12. Spatiotemporal analysis of epiphytotics of downy mildew of oilseed poppy in tasmania, australia.

Author

Scott JB, Hay FS, Wilson CR, Cotterill PJ, and Fist AJ

Abstract

Downy mildew, caused by Peronospora arborescens, has become the major disease affecting oilseed poppy (Papaver somniferum) since its first record in Tasmania in 1996. Two field trials conducted in 2000 and 2001 studied the progression and spatial distribution of downy mildew epiphytotics. The logistic and exponential models best described the progression of disease incidence and severity, respectively. Incidence and severity increased rapidly following canopy closure. In 2001, incidence increased from 0.16%, prior to canopy closure, to 100% at late flowering (40 days). Spatial analyses of epiphytotics were conducted by fitting the beta-binomial and binomial distributions, median runs analysis, and the spatial analysis by distance indices. All analyses demonstrated that the distribution of incidence and severity was strongly spatially aggregated from canopy closure until at least late flowering. These results suggest that secondary spread from a few primary infections is the major factor in epiphytotics.

Published
2003
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