ARS | Publication request: VIRULENCE OF PYTHIUM SPECIES ISOLATED FROM WHEAT FIELDS IN EASTERN WASHINGTON

Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: May 13, 2004
Publication Date: September 20, 2004
Citation: Higginbotham, R.W., Paulitz, T.C., Kidwell, K.K. 2004. Virulence of pythium species isolated from wheat fields in eastern washington. Plant Disease.88:1021-1026.

Interpretive Summary: Pythium root rot of wheat is an important disease that reduces yield in the Pacific Northwest. At least 10 different species have been shown to cause this disease. However, little is know about the relative virulence of these species, and which are the most important. This information is needed in order to screen germplasm for tolerance to this disease. A technique was developed to rate virulence in the greenhouse, based on the effect of the pathogen on shoot and root. Root measurements include root length and number of root tips, as determined by root scanning software. Isolates of nine Pythium species were tested on cultivars 'Chinese Spring' and 'Spillman'. Differences in virulence were detected among species and among isolates within species. Isolate Pythium debaryanum 90136 and P. ultimum 90038 were the most virulent, and may prove useful in future disease screening assays of Triticum germplasm.

Technical Abstract: Although Pythium root rot in wheat (Triticum aestivum L.) is well documented, limited information is available concerning which species of Pythium are most responsible for disease damage. The objective of this study was to examine the variation in virulence on wheat among isolates of Pythium collected from cereal grain fields in eastern Washington. Isolates of nine Pythium species were tested for virulence on spring wheat cultivars 'Chinese Spring' and 'Spillman'. Cultivars were planted into pasteurized soil infested with Pythium isolates and placed in a growth chamber maintained at a constant 16'C and ambient humidity. Plant height, length of the first true leaf and number of seminal roots were recorded and roots were digitally scanned to create computer files that were analyzed using WinRhizo software. Pythium isolates caused a significant reduction (P < 0.05) in the number of root tips, root length and length of the first leaf. Differences in virulence were detected among species and among isolates within species. Isolate Pythium debaryanum 90136 and P. ultimum 90038 were the most virulent, and may prove useful in future disease screening assays of Triticum germplasm.