Canadian Journal of Plant Pathology (1999) 21, 284-290

K. Xi, P.A. Burnett, T.K. Turkington, A. Tekauz and J.H. Helm (1999)
Determining quantitative resistance of barley cultivars at the seedling stage to net blotch caused by Pyrenophora teres
Canadian Journal of Plant Pathology 21 (3), 284-290
Abstract: Four barley (Hordeum vulgare L.) cultivars, Heartland, Harrington, Johnston, and Kasota, were compared at the seedling stage or reactions to the net and spot forms of net blotch caused by Pyrenophora teres f. teres and P. teres f. maculata, respectively. Effects of leaf wetness period, leaf position, and inoculum concentration on lesion development were investigated. The linear relationship between inoculum concentration and diseased leaf area was used to estimate inoculum concentrations causing 50% diseased leaf area (ED₅₀) on leaf 2 (the second seedling leaf) and causing 15% diseased leaf area (ED₁₅) on leaf 3 (third seedling leaf). Resistance of cultivars was compared on the basis of ED₅₀ and ED₁₅. The linear relationship of diseased leaf area with time was used to estimate the rate of lesion spread and to compare resistance. Lack of a significant linear relationship over time on leaf 3 for cvs. Heartland and Kasota inoculated with P. teres f. teres reflected resistance in these two cultivars. Both pathogens caused less than half the diseased area on leaf 3 as on leaf 2 in all cultivars. A mist period of 48 h tended to obscure the differences on leaf 2 between resistance and susceptibility. In general, there were positive correlations between the two pathogens based on ED₅₀ or ED₁₅. Pyrenophora teres f. maculata resulted in substantially higher ED₅₀ and ED₁₅ values on cvs. Johnston and Heartland, indicating that P. teres f. maculata was less virulent than P. teres f. teres on these cultivars. ED₅₀ and ED₁₅ values could be used to quantitatively differentiate moderately resistant cultivars from susceptible cultivars at the seedling stage.
(The abstract is excluded from the Creative Commons licence and has been copied with permission by the publisher.)
Link to article at publishers website
Database assignments for author(s): T. Kelly Turkington

Research topic(s) for pests/diseases/weeds:
general biology - morphology - evolution
resistance/tolerance/defence of host

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Pest and/or beneficial records:

Beneficial	Pest/Disease/Weed	Crop/Product	Country	Quarant.
	Pyrenophora teres	Barley (Hordeum vulgare)