D.J. Soares, D.F. Parreira and R.W. Barreto*

Departamento de Fitopatologia, Universidade Federal de Viçosa, Viçosa, Minas Gerais, Brazil, 36571-000

*rbarreto@ufv.br

Accepted for publication 08/08/05

Luffa cylindrica, known as smooth loofah, sponge gourd, dish-cloth gourd and vegetable sponge (local name: bucha), is a member of the Cucurbitaceae that is native to tropical Asia, possibly India. It was an important crop before the Second World War because of its use as a biological filter. In Brazil, loofah is a subsistence crop for small farmers. A downy mildew, caused by Pseudoperonospora cubensis, is one of the most important diseases for this crop (Purseglove, 1968), but although this fungus is a common cucurbit pathogen worldwide and also in Brazil, it has never been recorded on loofah in Brazil (Mendes et al., 1998).

Figure 1-2: Leaves of L. cylindrica showing downy mildew symptoms. 1. Adaxial view; 2. Abaxial view.	Figure 3-6: Close-up of a leaf of Luffa cylindrica with downy mildew symptoms. 3-4. Abaxial view showing vein-delimited lesions with water-soaked margins, and a whitish mass of sporangia and sporangiophores. 5-6. Adaxial view showing spots and scattered downy growth (arrowed).	Figure 7-8: Plasmopara australis ex Luffa cylindrica. 7. Sporangiophores. Bar = 100 µm; 8. Sporangiospores. Bar = 20 µm.

In May of 2005 plants of L. cylindrica were found showing moderate downy mildew symptoms in a small spontaneous population in the locality of Viçosa, state of Minas Gerais, Brazil. The lesions were amphigenous, initiating as slight discolorations of the tissues, become yellowish to necrotic, mostly vein-limited, with a clear water-soaked margin and a white, lanose to felt-like mass of fungal structures abaxially.(Fig. 1-6). A sample was deposited in the local herbarium (VIC 28797).

The fungus had the following morphology, as observed under the light microscope: Sporangiophores up to 460 µm long, aseptate, hialine, cylindrical, straight, with a slightly swollen base 10–18 µm, branches mostly at right angles and with truncated tips, sporangia deciduous, predominately oblong, 13–22 x 9–13 µm, l/w ratio (1.18–)1.36–1.90(–2.20), slightly papilate, sometimes with a small pedicel 1–2 µm long; sexual stage not found (Fig. 7-8). Morphology of this fungus places it unequivocally in the genus Plasmopara. Only two Plasmopara species are known on Cucurbitaceae: Plasmopara australis and Plasmopara orientalis. None of these were ever reported on L. cylindrica (Farr et al., No Date). P. australis is considered restricted to Argentina and N. America, while P. orientalis was recorded from far eastern Russia, China and Japan (Constantinescu, 2002). The combination of characters presented by the fungus on loofah matches well within the concept adopted by the former author for P. australis. This is, therefore, the first record of this fungus for Brazil and the first record of this fungus on L. cylindrica worldwide.

Acknowledgements
The authors would like to thank Dr José Ricardo Liberato for his valued assistance.

Constantinescu O, 2002. Plasmopara orientalis sp. nov. (Chromista, Peronosporales). Sydowia 54, 129-136.

Farr DF, Rossman AY, Palm ME, McCray EB, No Date. Fungal Databases, Systematic Botany & Mycology Laboratory, ARS, USDA. Retrieved June 24, 2005, from http://nt.ars-grin.gov/fungaldatabases/

Mendes MAS, Silva VL, Dianese JC, Ferreira MASV, Santos CEN, Neto EG, Urben AF, Castro C, 1998. Fungos em Plantas no Brasil. Brasília, Brazil: EMBRAPA-SPI.

Purseglove JW, 1968. Tropical Crops – Dicotyledons. England: Longman Group Ltd.

The British Society for Plant Pathology