– Erysiphe kusanoi on Celtis australis . A, Chasmothecia on the lower side of a leaf. B, Conidiophores with conidia. C, Chasmothecia with asci and coiled appendages. D, Appressoria (arrows). Bar = 20 μm (b & d) ; 50 μm (c). 

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... australis L. is a deciduous tree species belonging to family Cannabaceae, distributed widely from southern Europe, North Africa to Asia. The plant leaves and twigs are used as fodder in dry seasons while wood as good quality timber. Extracts from the tree are used to treat edema, headache and boils (Singh 1982, Hocking 1993). A powdery mildew species was observed on Celtis australis plant during a survey of plant diseases in the central region of Himachal Pradesh, India. The disease appeared as white mycelia on leaves with ascomata visible as small black to brown spherical structures upon examination of fresh or dried leaves using a dissecting microscope. The disease was studied further and described in the present study. Powdery mildew samples were collected from naturally infected Celtis australis leaves. The location of the collection Mandi, is a well-known region of Himachal Pradesh and popular for its fertile land and plain and hilly regions. The specimen is deposited at Department of Botany, Abhilashi Institute of Life Sciences (AILS), Mandi, Himachal Pradesh, India. The infected leaves were examined primarily with a hand-lens and then with a dissecting microscope for the presence of mildew symptoms. A piece of clear adhesive tape was placed on infected leaves, stripped off and then place on a microscopic slide with one drop of clear distilled water. The microscopic observations were carried out for morphological characteristics of mycelia on the host, appressoria, size and shape of conidia, conidiophores and chasmothecia. White mycelium observed on the leaves of Celtis australis was analysed in detail. Morphological and microscopic analysis of diseased samples revealed that this fungus belongs to section Uncinula of the genus Erysiphe. Further investigation identified it as Erysiphe kusanoi. Erysiphe kusanoi (Syd.) U. Braun & S. Takam., Schlechtendalia 4: 20, 2000 Fig. 1 ≡ Uncinula kusanoi Syd., Mém. Herb. Boissier 4: 4, 1900. = U. clintonii auct. p.p. ( sensu Salmon 1900 p.p.). = U. miyabei auct. p.p. ( sensu Tai & Wei 1932, on Hemiptelea ). Mycelium amphigenous, effuse, evanescent to almost persistent. Superficial hyphae branched, septate, hyaline, thin walled smooth, flexuous, 3.5 – 7.5 μm wide . Mycelial appressoria multilobed, coral-shaped, mostly in opposite pairs. Chasmothecia black, scattered, 95 – 130( – 180) μm in diameter when mature, with about 13 – 22 appendages, equatorial, stiff or mostly somewhat flexuous, about 0.75 times as long as the chasmothecial diameter slightly enlarged at the very base (7.5 – 10 μm) , then equal throughout or increasing somewhat to about 6 –8 μm towards the tip, circinate, coiled or hooked at the tip, hyaline, thin walled above, thick towards the base, smooth to rough. Asci 3 – 7, obovoid-saccate, 40 – 65 × (25 – )30 –50 μm, short -stalked, (3 – )5 – 7( – 8)-spored; ascospores ellipsoid-ovoid (-subglobose), 25 – 32.5 × 10 –18 μm , colourless. Conidiophores arising laterally and centrally from the mother cells, erect, up to about 90 μm long, width somewhat increasing from base to top. Foot-cells mostly curved at the base, occasionally slight, subcylindrical, 14 – 30 × 6 –9 μm, followed by 1– 2 cells that are shorter than the foot-cells, forming conidia singly. Conidia cylindrical or almost so, 25 – 40( – 45) × 11 –18 μm , germinating at terminal position, conidial appressoria multilobate, some two sided. Known distribution – on different Celtis species ( C. australis , C. biondii , C. koraiensis , C. sinensis , C. vandervoetiana and Hemiptelea davidii , Cannabaceae , in Asia (China, incl. Taiwan, Indian, Japan, Korea). Material examined – India, Himachal Pradesh, Mandi, 760 metres (2,495 ft), on leaves of Celtis australis L., 14 November 2013, Ajay Kumar Gautam (AILS 1001). Note – Based on morphology and microscopic dimensions of conidia, conidiophores, chasmothecia as well as asci and ascospores, it was concluded that powdery mildew on Celtis australis in Himachal Pradesh belongs to Erysiphe kusanoi (Braun & Cook 2012). This species is known from Uttar Pradesh, India (Ahmad et al. 2007, Hosagoudar & Agarwal 2009, Braun & Cook 2012), but it is new for Himachal Pradesh. Two other collections of powdery mildew on Celtis australis , pertaining to “ Uncinula clintonii Peck” recorded from Almora, Uttar Pradesh, now Uttarakhand (Pandey & Gupta 1983) and Pleochaeta indica (Ahmad et al. 1995), were made earlier in India. “ U. clintonii ” ( sensu Salmon 1900) on Celtis australis refers to E. kusanoi (Braun & Cook 2012). Ahmad N, Sarbhoy AK, Kamal. 1995 – New powdery mildews from India. Mycological Research 99, 374 – 376. Ahmad N, Agarwal DK, Bambawal OM, Puzari KC. 2007 – Erysiphaceae of India. Monographic Treatment. New Delhi. Braun U, Cook RTA. 2012 – Taxonomic Manual of the Erysiphales (Powdery Mildews). CBS Biodiversity Series No. 11. CBS, Utrecht, Netherlands. Hocking D. 1993 – Trees for drylands. Oxford & IBH Publishing Co. New Delhi. Hosagoudar VP, Argawal DK. 2009 – Powdery mildews of India – check list. New Delhi. Pandey KN, Gupta RC. 1983 – Powdery mildew of Kharik in Almora – a new record for India. Madras Agricultural Journal 70(1), 50. Salmon ES. 1900 – A monograph of the Erysiphaceae. Memoirs of the Torrey Botanical Club 9, 1 – 292. Singh RV. 1982 – Fodder trees of India. Oxford & IBH Co. New Delhi, ...