New Disease Reports
New Disease Reports (2008) 18, 6.
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First report of powdery mildew on Mexican sunflower in India

P. Baiswar*, R. Kumar, S. Chandra and S.V. Ngachan

*pbaiswar@yahoo.com&nbsp;

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Accepted: 19 Aug 2008

Tithonia diversifolia is a perennial garden plant coµmonly known as Mexican sunflower, belonging to the Asteraceae. Crude extracts of T. diversifolia leaves have intrinsic antimalarial properties (Ajaiyeoba et al., 2005).

Diseased plants of T. diversifolia were collected from Barapani, Meghalaya (1010 meters above mean sea level), were found to be heavily infected by powdery mildew during June and July 2007. Almost 70% of the plants surveyed in Barapani were infected. Disease symptoms included greyish white irregular patches consisting of epiphytic mycelia and conidia on both surfaces of the leaves. Symptoms were also present on stem, ray and disc florets (Fig. 1). Infected leaves later on turn necrotic (Fig. 2). A specimen has been deposited in Herbarium Cryptogamiae India Orientalis (HCIO), New Delhi, India (HCIO No. 47,968).

Hyphae were between 5-7 µm wide with nipple shaped appressoria (Fig. 3). Conidiophores were mostly erect containing a foot cell (37-64 x 7-11 µm) followed by two or three shorter cells (8-12 x 8-10 µm); conidia were cylindrical (26-34 x 14-18 µm) and produced in chains (Fig. 4). The basal septum of the conidiophore was just adjacent to mycelium. Fibrosin bodies were absent. Shoulder germination of conidia was also observed (Fig. 5). These morphological characters suggest this is the anamorph of Golovinomyces cichoracearum (Braun, 1987). No perfect stage (chasmothecium) was found. Pathogenicity was confirmed by dusting conidia on healthy potted plants of T. diversifolia, non-inoculated plants serving as control. Inoculated plants developed symptoms after a week whereas control plants remained healthy. Necrosis developed 18 days post-inoculation.

The only occurrence of powdery mildew on T. diversifolia was reported in Zambia (Hirata, 1986). To our knowledge, this is the first record of powdery mildew of T.diversifolia in India. This disease is also of regulatory significance since it has not been reported from adjoining countries like Sri Lanka where this crop is grown for the purpose of green manuring.

Figure1+
Figure 1: Symptoms of powdery mildew on Tithonia diversifolia plant
Figure 1: Symptoms of powdery mildew on Tithonia diversifolia plant
Figure2+
Figure 2: Symptoms of powdery mildew on Tithonia diversifolia leaf
Figure 2: Symptoms of powdery mildew on Tithonia diversifolia leaf
Figure3+
Figure 3: Hyphal appressoria of anamorph of powdery mildew on Tithonia diversifolia. Bar=20µm
Figure 3: Hyphal appressoria of anamorph of powdery mildew on Tithonia diversifolia. Bar=20µm
Figure4+
Figure 4: Conidiophores and conidia of anamorph of powdery mildew on Tithonia diversifolia, Bar=20µm
Figure 4: Conidiophores and conidia of anamorph of powdery mildew on Tithonia diversifolia, Bar=20µm
Figure5+
Figure 5: Germinating conidia of anamorph of powdery mildew on Tithonia diversifolia. Bar=20µm
Figure 5: Germinating conidia of anamorph of powdery mildew on Tithonia diversifolia. Bar=20µm

Acknowledgements

Authors would like to thank Dr. Prof. Uwe Braun for helping in identification of the pathogen.

References

  1. Ajaiyeoba EO, Bolaji OM, Akinboye DO, Falade CO, Gbotosho GO, Ashidi JS, Okpako LC, Oduola OO, Falade MO, Itiola OA, Houghton PJ, Wright CW, Ogundahunsi OA, Oduola AMJ, 2005. In vitro anti-plasmodial and cytotoxic activities of plants used as antimalarial agents in the southwest Nigerian ethnomedicine. Journal of Natural Remedies 5, 1-6.
  2. Braun U, 1987. A monograph of the Erysiphales (powdery mildews). Beihefte zur Nova Hedwigia 89, 1–700.
  3. Hirata K, 1986. Host range and geographical distribution of the powdery mildew fungi. Tokyo, Japan: Japan Science Society Press.
This report was formally published in Plant Pathology

©2008 The Authors