|WATERS, ORMONDE - Curtin University|
|LICHTENZVEIG, JUDITH - Curtin University|
|RYBAK, KASIA - Curtin University|
|OLIVER, RICHARD - Curtin University|
Submitted to: Crop and Pasture Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/1/2011
Publication Date: 8/25/2011
Publication URL: http://handle.nal.usda.gov/10113/58161
Citation: Waters, O.D.C., Lichtenzveig, J., Rybak, K., Friesen, T.L., Oliver, R.P. 2011. Prevalence and importance of sensitivity to the Stagonospora nodorum necrotrophic effector SnTox3, in current Western Australian wheat cultivars. Crop and Pasture Science. 62:556-562.
Interpretive Summary: Stagonospora nodorum blotch (SNB) caused by the fungal pathogen S. nodorum is a major disease of wheat in many parts of the world and particularly in Western Australia. SNB is characterised by the interactions of pathogen produced proteins called necrotrophic effectors (NEs) that interact with dominant host sensitivity genes. To date, five NE interactions have been reported in the SNB system. The identification of wheat lines lacking sensitivity to these NEs is a promising way to identify cultivars suitable for use in breeding for increased resistance to this economically important disease. Sensitivity to the NE SnTox3 was investigated in 61 current West Australian-adapted bread wheat (Triticum aestivum L.) varieties. Of the 61 varieties, 52 were highly sensitive varieties showing a prevalence of SnTox3 sensitivity in Western Australian wheat varieties. Susceptibility to an Australian isolate of S. nodorum had a high degree of correlation to the sensitive reaction to SnTox3. We conclude that a simple screen using NEs combined with simple greenhouse disease evaluation will allow breeders to select lines that are more resistant to SNB resulting in better higher yielding germplasm.
Technical Abstract: Stagonospora nodorum is a major pathogen of wheat in many parts of the world and particularly in Western Australia. The pathosystem is characterised by interactions of multiple pathogen necrotrophic effectors (NEs) (formerly host-specific toxins) with corresponding dominant host sensitivity loci. To date, five NE interactions have been reported in S. nodorum. Two proteinaceous NEs (ToxA and SnTox3) have been cloned and expressed in microbial systems. The identification of wheat lines lacking sensitivity to one or more NEs is a promising way to identify cultivars suitable for use in breeding for increased resistance to this economically important pathogen. The prevalence of sensitivity to the NE SnTox3 was investigated in 61 current West Australian-adapted bread wheat (Triticum aestivum L.) varieties. Infiltration of SnTox3 into seedling leaves caused a moderate or strong necrotic response in 52 varieties. Seven varieties were insensitive and two varieties exhibited a weak chlorotic response. Cultivars that were insensitive or weakly sensitive to SnTox3 were noticeably more resistant to the disease. The reaction of the 61 varieties to SnTox3 was very similar to crude S. nodorum SN15 culture filtrate demonstrating that SnTox3 is the dominant NE in this isolate. We conclude that a simple screen using both SnTox3 and ToxA effectors combined with simple greenhouse disease evaluation, will allow breeders to select lines that are more resistant to the disease, allowing them to concentrate resources on other still intractable breeding objectives.