Soybean Rust Caused by Phakopsora pachyrhizi Detected in the State of Campeche on the Yucatan Peninsula, Mexico

Abstract

Soybean rust caused by Phakopsora pachyrhizi Syd. & P. Syd is a destructive foliar disease of soybean (Glycine max L), which was first confirmed in North America in Louisiana during 2004 (4). Soybean rust (SBR) has also been reported late in the growing season as far north as Illinois, Indiana, and Iowa. SBR was first confirmed in Mexico in 2005 in the state of San Luis Potosi on soybean (3) and subsequently reported in the states of Tamaulipas, Veracruz, and the southwestern coast of Chiapas. Symptoms of SBR were observed on leaves of multiple, nearly mature soybean plants near the city of Campeche (19.72796°N, 90.0771°W) on the Gulf Coast of the Yucatan Peninsula during November 2008. Angular and irregular chlorotic lesions on leaves contained necrotic spots and pale brown, erumpent, cone-like uredinia with a central opening. Ellipsoid to obovoid, echinulate, light tan urediniospores (10 to 13 × 16 to 18 μm) were observed microscopically. DNA was extracted from leaf tissue containing uredinia and from asymptomatic tissue with the DNeasy Plant Mini Kit (Qiagen, Valencia, CA). P. pachyrhizi was confirmed in the symptomatic leaves by a PCR assay with Ppm1/Ppa2 primers, but not from the asymptomatic leaves (1). Subsequently, the DNA extracted from symptomatic and asymptomatic leaf tissues was tested again in another laboratory by a specific quantitative PCR assay (1), and positive results for the presence of soybean rust were obtained only from the symptomatic tissue. As a final confirmatory step, amplified DNA from the PCR assay was sequenced, and the results matched P. pachyrhizi sequences in the GenBank database. To our knowledge, these observations confirm for the first time the presence of P. pachyrhizi in the state of Campeche of southern Mexico. Although it was confirmed on soybean during 2008, it is not known how long the pathogen has been present or which other hosts may be infected there. The presence of SBR on the Yucatan Peninsula is significant because of its potential effects on local plant hosts. In addition, the climate allows possible year-round survival of the pathogen and long-distance transport of urediniospores to the United States. Potential transport of SBR spores from this part of Mexico to the United States has been reported through the application of NOAA's HYSPLIT (Hybrid Single Particle Lagrangian Integrated Transport) model and atmospheric back-trajectory analysis (2). References: (1) R. D. Frederick et al. Phytopathology 92:217, 2002. (2) S. V. Krupa et al. Plant Dis. 90:1254, 2006. (3) A. C. Rodriguez et al. Plant Dis. 90:1260, 2006. (4) R. W. Schneider et al. Plant Dis. 89:774, 2005.

Identification of daylily rust (Puccinia hemerocallidis) and characterization of resistance of five genotypes

“…Las royas son parásitos obligados y altamente específicos al hospedante; en algunas especies de royas, las formas especiales y razas fisiológicas son definidas de acuerdo con la especificidad del hospedante y cultivares (Li et al, 2007). En el caso de P. hemerocallidis, no se ha reportado especificidad al hospedante a nivel de razas fisiológicas por lo que, no sería sorprendente la existencia de tal especialización patogénica en este patosistema ya que es similar a aquellos que involucran royas en diferentes cultivos de importancia económica (Leonard y Szabo, 2005;Soto-Estrada et al, 2005;Yáñez et al, 2009), pero es necesario realizar más estudios para demostrar este aspecto.…”

“…tritici) y roya de la hoja del trigo (P. triticina) la recombinación ge-special forms and physiological races are defined according to the host specificity and cultivars (Li et al, 2007). In the case of P. hemerocallidis, there are no reports on its host specificity, so it would not be surprising to find such pathogenic specialization in this pathosystem, considering that it is similar to those that involve rusts in different economically important crops (Leonard and Szabo, 2005;Soto-Estrada et al, 2005;Yáñez et al, 2009), but further studies must be conducted to demonstrate this aspect.…”

Composición química y degradación de cuatro especies de Pennisetum sp

“…No ano de 2002 a doença apareceu no Brasil (Yorinori, et al 2002b;Costamilan, et al 2002;Reis et al, 2002) e na Argentina (Rossi, 2003). Em 2003 foi relatada na Bolívia (Navarro et al, 2004) e na Colômbia (Reis et al, 2006a), progredindo em 2004 para o Uruguai (Stewart et al, 2005) e 2005 no Equador (Sotomayor-Herrera, 2005), México (Cárcamo-Rodríguez et al, 2006;Yáñez-Morales et al, 2009) e Estados Unidos (Schneider et al, 2005). Atualmente, a ferrugem asiática está presente em todos os países onde a soja é cultivada.…”