Wednesday, 9 November 2005

Development of a Detached Leaf Assay for Stripe Rust Resistance Screening.

Aleksandre Loladze1, Kimberly Garland Campbell2, and Xianming Chen2. (1) Washington State University, 201 Johnson Hall, WSU, Pullman, WA 99164, (2) USDA ARS, 209 Johnson Hall, WSU, Pullman, WA 99164

Stripe rust (Puccinia striiformis F. sp. Tritici) is one of the major diseases of wheat (Triticum aestivum L. em Thell.) worldwide causing significant yield and quality loss. Detached leaf assay experiments have been developed to screen for resistance to Fusarium head blight, Stagonospora nodorum and Mycosphaerella graminicola resistance. Although detached leaf assays can be more efficient than field-based screening, a detached leaf assay has not been previously developed to screen for resistance to stripe rust. This study was conducted to develop a detached leaf assay to screen for resistance to Puccinia striiformis on agar media in Petri dishes. Treatments consisted of water-gar media containing the plant senescence retardants Benzimidazole (100 mg l-1) and Kinetin (10 mg l-1) plus the fungicides Dithiocarbamate (0.1 mg ml-1) and Pentachloronitrobenzene (0.33 g l-1) in all combinations. 3-5 cm long segments of the second leaves of 14 d old seedlings were surface disinfected, placed on agar surface, inoculated with stripe rust spores (PST-45) and placed into a dark growth chamber at 100C for 24 h. The temperature was increased to 150C and a 12 h photoperiod for the next 20 days. Infection was rated at 14 and 21 d after inoculation. A most suitable agar media was identified (0.5% water-agar and 10 mg l-1 Kinetin) that allowed the leaf segments to avoid senescence longer and at the same time did not affect stripe rust development. A second detached leaf assay experiment for testing various reactions of different wheat genotypes to stripe rust inoculation is being carried out.

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