Introducing two medicinal plants, Rosa canina and Rosa elymatica, as new hosts for Podosphaera panosa in Iran

The genus Rosa from Rosaceae family has 18 species in Iran of which 12 are self-growing shrubs and the species R. persica, R. orientalis, R. pulverulenta, R. iberica, R. hemisphaeria, R. boissieri, R. elymatica grow in many countries as well. Many forms & cultivars from the genus grow in temperate and cold areas of Iran. In this survey, an important disease that damage these plants in Lorestan province was found and powdery milews on two species of this genus namely Rosa canina L. & R. elymatica Boiss & Hausken were identified. The symptoms include white, dusty appearance on upper surface of leaves, petals, fruits and stem of the infected plants. Mycelium of the causal agent is white in colour, and there is clistothecium into the hyphae. There is few appendage beneath the cleistothecium. Cleistothecium is 100-157 µm, asci have ellipsoid shape and are 71-105×90-195 µm. Ascospore is ellipsoid to egg shape and 20-21×22-39 µm in size. Conidia are ellipsoid egg to barrel shape and have 9-14×19-30 µm size. By comparing the characters of the disease agent to special key for this fungus (Braun 1978 , Braun & Takamatsu 2000), the fungus was idendified as Podosphaera panosa (Lév.) Braun & takamatsu with synonyme of Sphaerotheca parasa (Wallr. Fr.) Lév. The fungus has been reported so far on plant species of Rosasp., Hultemia persica (Michx. ex Juss.) Staef (syn :Rosa persica MichX. ex Juss.) & R. multiflora Dum. but this is the first report of occurance of this fungus on the two plant species, Rosa canina and R. elymantica from Iran.