in 2003, and a specific melon cultivar (C. melo var. acidulus 'PI 313970') found resistant to it, then used for backcrossing to increase resistance in other cultivars. Such modern selective breeding of plants for phytopathological resistance to particular fungal races involves a great deal of genetic research; this PI 313970 versus race S case involved multi-stage hybridization to propagate a recessive gene, pm-S in successive generations, and how this may affect other recessive and codominant genes for resistance to other races of P. xanthii "remains to be determined". A 2004 literature review regarding powdery mildew races that parasitize various cucurbit plants concluded that "race identification is important for basic research and is especially important for the commercial seed industry, which requires accuracy in declaring the type and level of resistance ... in its products". However, identifying specific races was seen as having little utility in horticulture for choosing specific cultivars, because of the rapidity with which the local pathogen population can change geographically, seasonally, and by host plant. At least three other Erysiphaceae fungi can cause powdery mildew in cucurbits: The most frequent, after P. xanthii, is Erysiphe cichoracearum, the former primary causal organism throughout most of the world. Podosphaera fusca is another, sometimes considered synonymous with P. xanthii. Cucumbers in greenhouse environments have also been reported to be susceptible to Leveillula taurica. Lilacs Microsphaera syringae is a fungus that can cause powdery mildew in lilac. Strawberries Podosphaera aphanis is the cause of powdery mildew in strawberries and other Rosaceae like Geum rivale (the water avens) Tree leaves Sawadaea tulasnei is a fungus that causes powdery mildew on tree leaves. This fungus attacks the leaves of the Acer platanoides (Norway maple) in North America, Great Britain, and Ireland, Acer palmatum (also known as the Japanese maple or smooth Japanese maple). Oregon grape Erysiphe berberidis is a fungus that causes powdery mildew on Oregon grape leaves. Arabidopsis Golovinomyces orontii causes powdery mildew on Arabidopsis (rockcress) leaves. Cannabis Caused by several fungi including Golovinomyces ambrosiae (syn. G. spadiceus) and Podosphaera macularis. See also . Hyperparasites of powdery mildew In the family Sphaeropsidaceae of the Sphaeropsidales fungi, species of the genus Cicinnobolus are hyperparasites of powdery mildew. Ampelomyces quisqualis is an anamorphic fungus that is a hyperparasite of powdery mildews. This parasitism reduces growth and may eventually kill the mildew. Research on biological control of powdery mildews (especially in high-value crops such as