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

Abstract

Orange rust, Puccinia kuehnii (W. Krüger) E.J. Butler, is an important disease of sugarcane (complex hybrid of Saccharum L. species) that causes up to 53% yield loss (3), and can eliminate sugarcane clones in breeding programs. Initially confined to the Asia-Oceania region, P. kuehnii was reported in Florida in June 2007 (2) followed by confirmation in Central and South America. Orange rust pustules were observed on August 5, 2011, in commercial sugarcane fields located in the Ecuadorian Pacific coast of South America. Pustules were observed on cultivar SP79-2233 and sugarcane clones of the CINCAE breeding program (EC06-351, EC06-340, and EC01-744). Low levels of disease incidence and severity were observed in the sugarcane germplasm. Observation under a light microscope showed typical irregularly echinulate urediniospores that were pale in color with thickened apices and paraphyses inconspicuous to absent, such as those reported to be P. kuehnii (4). DNA of urediniospores were extracted and amplified using Pk1F and PK1R qPCR primers (5). Additionally, the 28s large ribosomal subunit DNA was sequenced (1), resulting in a qPCR and 100% sequence identity with a partial sequence of the P. kuehnii 28S ribosomal RNA gene, accession GU058010 (932/932 base pairs, GenBank Accession No. KF202306). Based on urediniospore morphology, DNA amplification, and sequence analysis, the causal agent of the rust observed in Ecuador was confirmed to be P. kuehnii. Commercial varieties have not yet shown symptoms of infections. However, a survey conducted in 2011 and 2012 showed an increase of disease severity from 3% to 28% in the susceptible cv. SP79-2233. Disease symptoms were evident from stalk growth to maturity (7 to 12 months), especially at the beginning of the harvesting season. To our knowledge, this is the first report of the presence, distribution, and disease spread by the sugarcane orange rust pathogen P. kuehnii in Ecuador. References: (1) M. C. Aime. Mycoscience 47:112, 2006. (2) J. C. Comstock et al. Plant Dis. 92:175, 2008. (3) J. C. Comstock et al. ASSCT. 29:82, 2009. (4) L. Dixon and L. Castlebury. Orange Rust of Sugarcane – Puccinia kuehnii. Syst. Mycol. Microbiol. Lab. Retrieved from /sbmlweb/fungi/index.cfm, August 12, 2011. (5) N. C. Glynn et al. Plant Pathol. 59:703, 2010.

Reaction of sugarcane varieties to orange rust (Puccinia kuehnii) and methods for rapid identification of resistant genotypes

“…RB72454 and SP89-1115 were the most susceptible ones, confirming the observations of Barbasso et al (2010) and Araújo et al (2013). SP79-2233 was also susceptible, which is corroborated by Ovalle et al (2008), Chavarría et al (2009 and Garcés et al (2014), although its AUDPC and MS% were lower than that of RB72454 and SP89-1115 in our study.…”

“…Sixteen of them were selected based on the planted area in the states of São Paulo and Mato Grosso do Sul in 2010 (Chapola et al 2011); these states together accounted for 60 % of the national sugarcane production in 2015 (CONAB 2015). Variety SP79-2233 was included in the tests due to its susceptibility to orange rust as reported in other countries (Ovalle et al 2008(Ovalle et al , 2009Chavarría et al 2009;Garcés et al 2014). Similarly, varieties RB72454 and SP89-1115 were considered susceptible to the disease in Brazil (Barbasso et al 2010).…”

Identifying Quantitative Trait Loci (QTLs) and Developing Diagnostic Markers Linked to Orange Rust Resistance in Sugarcane (Saccharum spp.)

“…Previously restricted to Asia, and the Pacific regions, sugarcane orange rust has also been detected in multiple countries in the western hemisphere ( Comstock et al, 2008 ; Ovalle et al, 2008 ; Chavarria et al, 2009 ; Flores et al, 2009 ; Barbasso et al, 2010 ; Cadavid et al, 2012 ; Garcés et al, 2014 ). The outbreak of this disease could result in devastating economic loss, with an estimation of Aus$150–210 million in 2000 in Australia ( Braithwaite et al, 2009 ).…”

“…Orange rust, caused by Puccinia kuehnii , was first reported in Australia more than 100 years ago; however, this disease only began to draw attention due to its devastating epidemic in 2000 on a major Australian sugarcane cultivar Q124 ( Braithwaite et al, 2009 ). Orange rust was first identified in the Western Hemisphere, specifically in Florida, United States, in 2007 ( Comstock et al, 2008 ) and shortly after in Guatemala ( Ovalle et al, 2008 ), Mexico, El Salvador, Panama ( Flores et al, 2009 ), Costa Rica, Nicaragua ( Chavarria et al, 2009 ), Brazil ( Barbasso et al, 2010 ), Colombia ( Cadavid et al, 2012 ), and recently Ecuador ( Garcés et al, 2014 ). The disease immediately became an emerging threat to sugarcane production and breeding programs since its discovery ( Comstock et al, 2008 , 2010 ), which can cause up to 50% cane yield loss in its susceptible hosts ( Magarey et al, 2011 ).…”

Distinguishing sporulating and nonsporulating lesions as a method for evaluating the resistance of sugarcane genotypes to orange rust

“…In susceptible varieties, yield losses greater than 50% were reported (Araújo et al ., ). After detection in Brazil (Barbasso et al ., ), orange rust was also reported in other South American countries including Colombia (Cadavid et al ., ), Ecuador (Garcés et al ., ) and Argentina (Funes et al ., ).…”