First Report of Orange Rust of Sugarcane Caused by Puccinia kuehnii in Guyana

Abstract

In September 2012, orange uredinial lesions (0.3 mm to 1.2 mm in length x 0.1 mm to 0.3 mm in width; mean of 0.6 mm ± 0.16 mm in length x 0.2 mm ± 0.01 mm in width) surrounded by dark, reddish-brown necrotic tissue and running parallel to the leaf venation were observed on leaves of a major commercial sugarcane (Saccharum spp. L. hybrid) cultivar - DB7869, grown on an estate, in east Berbice-Corentyne, Guyana. Golden yellow to orange coloured obovoid urediniospores (27.5 µm to 60.0 µm in length x 17.5 µm to 37.5 µm in width; mean of 38.0 µm ± 7.82 µm in length x 24.0 μm ± 3.31 µm in width) with distinct apical wall thickenings were visible using both light and scanning electron microscopy based on a random sample of 30 urediniospores. These features were characteristic of Puccinia kuehnii (W. Kruger) E.J. Butler, the causal agent of orange rust of sugarcane (Virtudazo et al. 2001). Isolated DNA from symptomatic dried leaf material was amplified using P. kuehnii species specific primers (Pk1-F/Pk1-R) targe...