First Report of Orange Rust Disease of Sugarcane in the Dominican Republic.

In June 2011, uredinial leaf lesions typical of rust disease were observed on the two main commercial sugarcane (a complex Saccharum spp. L. hybrid) cultivars CR87339 (30% of acreage), CR83323 (17% of acreage) as well as cultivars BR9806, BR9816, and BT88133 at La Romana in the Dominican Republic. Morphological analysis of the lesions using both light and scanning electron microscopy identified obovoid spores (36 × 24 μm) with apical wall thickenings which are distinctive features of Puccinia kuehnii (W. Krüger) E.J. Butler, the causal agent of orange rust disease of sugarcane (4). DNA from dried leaf samples containing urediniospores was extracted and PCR-amplified using the P. kuehnii specific primers (Pk1-F/Pk1-R) (1). A 527-bp fragment representing the ITS rDNA region was obtained and sequenced. A GenBank BLAST search of the database of the consensus sequence showed 100% sequence identity to the GenBank accession GU564421 along the entire sequence length. Based on field observations, urediniospore morphology, PCR amplification, and DNA sequence analysis, the causal agent of the observed rust disease was therefore confirmed to be P. kuehnii. Since its initial discovery, orange rust disease has been observed in 15 additional sugarcane cultivars at the Central Romana Sugarcane Corp. Ltd. at La Romana and has persisted during the years 2012 and 2013. Central Romana Sugarcane Corp. Ltd. is the largest sugarcane grower (70,000 ha) and sugar producer (430,000 t annually) in the Caribbean. Although an economic impact assessment of the disease has not been performed at La Romana, orange rust disease has the potential to cause significant yield loss (1). Orange rust has been reported previously in several parts of Central America and in the neighboring islands of Cuba and Jamaica in 2010 (2,3). To our knowledge, this is the first confirmed report of orange rust disease of sugarcane in the Dominican Republic. References: (1) J. C. Comstock et al., J. ASSCT. 29:82, 2009. (2) N. C. Glynn et al. Plant Pathol. 59:703, 2010. (3) L. Pérez-Vicente et al. Plant Pathol. 59:804, 2010. (4) E. V. Virtudazo et al., Mycoscience 42:167, 2001.