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Prevalence and importance of sensitivity to the Stagonospora nodorum necrotrophic effector SnTox3, in current Western Australian wheat cultivars.

Waters, Ormonde D.C., Lichtenzveig, Judith, Rybak, Kasia, Friesen, Timothy L., Oliver, Richard P.
Crop & pasture science 2011 v.62 pp. 556
Leptosphaeria nodorum, Triticum aestivum, breeding, cultivars, culture filtrates, greenhouses, host specificity, hosts, leaves, loci, pathogens, screening, seedlings, toxins, wheat, Western Australia
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.