Meadowsweet rust gall on the petioles and / or midrib veins. The rust has a severe effect on the survival of meadowsweet seedlings. Meadowsweet rust gall Triphragmium ulmariae is a species of fungus in the Sphaerophragmiaceae family. It causes meadowsweet rust gall, which develops as a chemically induced swelling, arising from the lower surface of the meadowsweet leaves. This common gall is caused by the foliar 'rust' fungus "Triphragmium ulmariae" (DC.) Link, 1825 . The fungus attacks the petioles and / or midribs of the perennial meadowsweet ("Filipendula ulmaria") plant, a member of the family Rosaceae, causing swelling and distortion. Sori develop with
True-breeding organism plants for gardeners are F1 hybrids, which if propagated from seed will produce F2 hydrids which are quite different from their parents; the F1 hybrids therefore don't breed true. True-breeding organism A true-breeding organism, sometimes also called a purebred, is an organism that always passes down certain phenotypic traits (i.e. physically expressed traits) to its offspring of many generations. An organism is referred to as true breeding for each trait to which this applies, and the term "true-breeding" is also used to describe individual genetic traits. In Mendelian genetics, this means that an organism must be homozygous for every trait