First report of orange rust of sugarcane caused by Puccinia kuehnii in Guyana.
In September 2012, orange uredinial lesions (0.3 to 1.2 mm long × 0.1 to 0.3 mm wide; mean 0.6 ± 0.16 mm long × 0.2 ± 0.01 mm wide) 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. hybrid) cultivar, DB7869, grown on an estate in east Berbice-Corentyne, Guyana. Based on field observations, urediniospore morphology and sequence analysis of the rDNA internal transcribed spacer region, the causal agent was identified as P. kuehnii. Since its initial discovery, orange rust has been observed on another important commercial cultivar, DB9633, at the same estate in east Berbice-Corentyne, and has also spread to another estate on the west bank of Demerara. Guyana's sugar industry, the country's largest employer and the Caribbean's second largest sugar producer (231 071 t in 2015; mean of 229 561 t/year) accounts for 18% of its domestic agricultural production and its third largest foreign revenue earnings. Several other sugar-producing countries in the Caribbean including Cuba, Jamaica and the Dominican Republic have all confirmed the presence of this disease. This is thought to be the first confirmed report of orange rust of sugarcane in Guyana.