Abstract
Graduate School of Bioresources, Mie University,Kurima-machiya 1577, Tsu, Mie Pref. 514-8507, JapanEcheveriaagavoidesbelongstothefamilyofCrassulaceae.Itiscommonlygrown as an ornamental plant in India. Diseased leaves of E. agavoidescollected from Shillong, Meghalaya (North East India) were found to beheavilyinfectedbypowderymildewduringJanuary2008.Almost70%ofthe plants surveyed were found infected in Shillong. Disease symptomsincluded greyish white circular patches consisting of epiphytic mycelia andconidia, mostly on the upper surface of leaves. Infected leaves later onturnednecrotic.Heavyinfectionresultedinseveredefoliation.Avoucherspecimen has been deposited in CABI Bioscience UK Centre (IMI No.396393).Microscopic observations revealed conidia were formed singly, whichruled outthepossibilityofGolovinomycesorontii,Neoerysiphe galeopsidisand Podosphaera macularis reported on Crassulaceae (Farr et al., 2005).Hyphae were between 4AE3–5AE2 lm wide with multilobed appressoria.Conidiophores were mostly erect containing a foot cell (22AE4–36AE7 · 12AE4–15AE2 lm) followed by two or three short cells, and conidia were cylindricalin shape (30AE6–46AE2 · 15AE2–19AE3 lm). Fibrosin bodies were absent.Conidiaproducedshortgermtubesontheapicalportionterminatinginlobedappressoriaupongermination.Basedonthesemorphologicalcharactersthepowdery mildew belongs to the genus Oidium subgenus Pseudoidium ,theanamorphof Erysiphe (Cooketal.,1997).Noperfectstage(chasmothecium)wasfoundtobeassociatedwiththisfungus.PathogenicitywasconfirmedbydustingconidiaonhealthypottedplantsofE. agavoides, with uninoculatedplants serving as controls. Inoculated plants developed symptoms after aweekwhereascontrolplantsremainedhealthy.In GenBank, DNA sequences of the rDNA ITS region (Acession No.AB467356) and D1/D2 domains of the 28 rDNA (AB467357) wereunique. The ITS sequences (EF434394, EU185636 to EU185641) of ananamorph of Erysiphe reported on various members of the Crassulaceaein the UK and Hungary were found to be different from the presentsequence (Henricot, 2008). However, these sequence analyses support themorphological observation that the fungus belongs to Oidium subgenusPseudoidium.This is the first record of powdery mildew on Echeveria in India.This disease is also of regulatory significance since this part of India(North East) shares its boundaries with Nepal, China, Burma, Bhutanand Bangladesh, and this disease has not been reported from any ofthese countries.References
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