DRY TWIST: A SYSTEM OF CULTURING RUSTS FROM SINGLE SPORES

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Abstract
The dry twist system of culturing rust from a single urediospore or aeciospore provides a simple, rapid, and straightforward procedure which requires a minimum of manual dexterity. Two successive crops of urediospores, the first used to infect differential varieties for race identification, and the second crop for collection of a pure increase of the culture, can be produced directly from the single spore.The system combines three separate techniques: isolation of single spores from dialysis tubing cellophane; inoculation of single spores by the dry twist method, which involves drawing the needle tip lightly up along the dry leaf blade with a twisting motion; and the subsequent development of infection, first on the attached leaf and then on the excised leaf blade floating on benzimidazole in a closed petri dish. Dry twist is recommended for general use in the isolation, purification, and increase of rust cultures.