POWDERY MILDEW CAUSED BY LEVEILLULA SAXAOULI ON ILJINIA REGELII IN THE GURBANTUNGGUT DESERT OF XINJIANG

Abstract

Iljinia regelii (Bunge) Korov., family Chenopodiaceae, one of the most important stabilizers of sand dunes for the control of desertification only occurs in the desert area of Central Asia (Zhu et al., 2003). In summer 2014, severe outbreaks of a previously unknown powdery mildew were observed in the Gurbantunggut desert in Xinjiang (China). The upper surface of leaves and stems was covered with a white mycelium. In severe infections, distortion of the leaves was observed. Conidia were single, dumbbell-like, cylindrical with cingulum-like rings near the apex and base, 41-63×16-25 μm in size. Chasmothecia 158-239 μm in diameter were scattered or gregarious, often immersed in mycelium patches, had appendages mostly poorly developed, mycelioid, simple or irregularly branched, 40-148 μm long. Asci were numerous (10 to 32), ellipsoid-obovoid, saccate-clavate, 80-112×30-49 μm in size, stalked and contained two ellipsoid-ovoid, colourless ascospores measuring 23-41×14-27 μm. These morphological characters were consistent with those of Leivellula saxaouli (Braun and Cook, 2012). To confirm the identification, the internal transcribed spacer (ITS) rDNA was amplified and sequenced, and deposited in GenBank (accession No. KP345898). Comparison with sequences available in database revealed that the ITS sequence shares 99% similarity with that of L. saxaouli recorded in Haloxylon sp. from Iran (accession No. AB044382.1) (Khodaparast et al., 2001). Based on the host, morphology, and ITS sequence analysis, the fungus was identified as L. saxaouli. To our knowledge, this is the first report of L. saxaouli causing powdery mildew on Iljinia regelii. The presence of L. saxaouli on I. regelii could pose a potential threat to the fragile ecological systems of desert areas of Xinjiang, China.