First Report of Phakopsora pachyrhizi, the Causal Organism of Soybean Rust in the Province of Misiones, Argentina

Abstract

In April 2002, Phakopsora pachyrhizi Sydow was observed for the first time in L. N. Alem, in the Province of Misiones, Argentina. Misiones is nearly surrounded by Paraguay and Brazil, where P. pachyrhizi was discovered recently (2) and where it is a serious disease (3). Symptoms were observed on leaves in the upper half of plants at the R6 stage in a soybean research field trial. Symptoms included reddish-brown lesions on leaves especially on the abaxial surface, and uredinias were observed in the lesions with a 10× lens. Leaf defoliation was observed due to the disease after the R5 stage, and the enviroment (high humidity and air temperatures) was particularly conducive to the disease. The field trial area was 2,500 m2 and included soybean genotypes of maturity groups V to IX. Symptoms were detected in the later maturity groups. Field trials were surrounded by kudzu (Pueraria sp.), which is a common weed introduced in South America as a forage plant by Asian farmers, and it was reported as the main host of this pathogen in Paraguay (2). To confirm the identity of the pathogen, leaf samples from the middle part of plants were collected and sent to the Foreign Disease-Weed Science Research Unit, Ft. Detrick, MD. Samples were analyzed using a real-time polymerase chain reaction assay (1). Identification of P. pachyrhizi was confirmed the last week of May, 2002 (R. Frederick, personal communication). The soybean production area in Misiones is a small area in Argentina lying 600 km northeast of the main soybean area in the north central part of the country. SENASA (Servicio Nacional de Sanidad Vegetal [Nacional Service of Plant Health]) and SAGPYA (Secretary of Agriculture) were formally informed about these results on June 19, 2002. A program to assess the risk of disease spread is under development. References: (1) R. D. Frederick et al. Phytopathology 92:217, 2002. (2) W. Morel Paiva. AnaisII Congresso Brasilero de Soja e Mercosoja. Foz de Iguazu, Brazil, 2002. (3) T. Yorinori. Anais II Congresso Brasilero de Soja e Mercosoja. Foz de Iguazu, Brazil, 2002.

Asian soybean rust in Brazil: past, present, and future

“…The disease was first reported in Africa in the mid-1990s (Pretorius et al, 2001). Then, in 2001, it was found in Paraguay and in the west of the state of Paraná, Brazil, spreading, within three years, throughout South America (Rossi, 2003;Yorinori et al, 2005). In 2004, ASR was reported in the continental United States (Schneider et al, 2005).…”

Pathogenic Variation of South American <i>Phakopsora pachyrhizi</i> Populations Isolated from Soybeans from 2010 to 2015

“…Soybean rust can result in a 10%-80% reduction in yield or losses of over 80%, particularly when the disease develops under preferable environmental conditions for P. pachyrhizi (Hartman et al 2005, Levy 2005, Li et al 2010, Pennisi 2010, Rosa et al 2015, Yorinori et al 2005. Since the first outbreak of soybean rust caused by P. pachyrhizi in Paraguay and Brazil in 2001 and in Argentina in 2003 (Ivancovich 2005, Rossi 2003, Yorinori et al 2005, it has rapidly spread to most of the soybean fields throughout South America, and has continuously impacted soybean production in the region, resulting in tremendous economic losses.…”

Models and applications for risk assessment and prediction of Asian soybean rust epidemics

“…From Africa, the fungus was thought to have spread into South America, affecting late-season soybean plants in Paraguay andBrazil in 2001 (Yorinori , 2002), and in northern Argentina in 2002 (Rossi, 2003). In November 2004 Asian soybean rust was found in the continental United States, the last major soybean production area where it had not been previously reported (Schneider , 2005).…”