Evaluation of USDA Soybean Germplasm Accessions for Resistance to Soybean Rust in the Southern United States

Crop Science ◽  
2011 ◽  
Vol 51 (2) ◽  
pp. 678-693 ◽  
Author(s):  
D. R. Walker ◽  
H. R. Boerma ◽  
D. V. Phillips ◽  
R. W. Schneider ◽  
J. B. Buckley ◽  
...  
Crop Science ◽  
2014 ◽  
Vol 54 (4) ◽  
pp. 1673-1689 ◽  
Author(s):  
David R. Walker ◽  
Donna K. Harris ◽  
Zachary R. King ◽  
Zenglu Li ◽  
H. Roger Boerma ◽  
...  

Plant Disease ◽  
2008 ◽  
Vol 92 (5) ◽  
pp. 767-771 ◽  
Author(s):  
T. L. Slaminko ◽  
M. R. Miles ◽  
R. D. Frederick ◽  
M. R. Bonde ◽  
G. L. Hartman

Phakopsora pachyrhizi, the causal organism of soybean rust, was first found in the continental United States in 2004 and has been found on soybean, kudzu, Florida beggarweed, and three Phaseolus species in the field. The pathogen has been reported to occur on more than 90 legume species worldwide and it is likely to infect native and introduced legume species in the United States. The objective of this study was to determine if 176 species representing 57 genera of legumes, the majority of which are either native or naturalized to soybean-growing areas of the United States, could be hosts of P. pachyrhizi. Between one and three accessions of each species, a total of 264 accessions, were inoculated with a mixture of four isolates of P. pachyrhizi. Severity and sporulation were rated on a 1-to-5 scale at 14 and 28 days after inoculation. P. pachyrhizi was confirmed by the presence of sporulating uredinia and/or immunological assay on 65 new species in 25 genera; 12 of these genera have not been reported previously as hosts. Many of the newly identified hosts grow in the southern United States, and like kudzu, could serve as overwintering hosts for P. pachyrhizi.


Plant Disease ◽  
2010 ◽  
Vol 94 (4) ◽  
pp. 477-477 ◽  
Author(s):  
C. A. Bradley ◽  
R. A. Hines ◽  
N. R. Pataky ◽  
J. S. Haudenshield ◽  
G. L. Hartman

Soybean rust, caused by Phakopsora pachyrhizi Syd., first was observed in the continental United States during 2004 on soybean (Glycine max (L.) Merr.) in Louisiana (4), and on kudzu (Pueraria montana (Lour.) Merr. var. lobata (Willd.) Maesen & Almeida) in Florida (2). Kudzu is a leguminous weed that is prevalent in the southern United States with its range extending northward into other states including Illinois. In October 2009, a kudzu patch located in Pulaski County in southern Illinois was investigated for the presence of soybean rust. Twenty-five leaflets were collected, and the abaxial sides of leaflets were evaluated visually for the presence of uredinia with a dissecting microscope. Uredinia and urediniospores were found on two leaflets. When viewed with a compound microscope, urediniospores were hyaline, echinulate, and measured 20 × 25 μm. On the basis of uredinia and urediniospores, the disease tentatively was identified as soybean rust caused by P. pachyrhizi. To confirm the identification, one leaflet with pustules was assayed with a Soybean Rust QuickStix Diagnostic Kit (Envirologix, Portland, ME). For the other leaflet, the area of the pustule was excised (approximately 28 mm2) and an area of the leaflet at the margin on the opposite half of the leaflet with no visible pustule (approximately 54 mm2) was excised. DNA was extracted from the excised areas of the leaflet for confirmation by quantitative PCR (Q-PCR) using primers and probe specific to P. pachyrhizi and P. meibomiae (Arthur) Arthur (1). Both the QuickStix Diagnostic Kit and the Q-PCR confirmed the diagnosis as soybean rust caused by P. pachyrhizi. Q-PCR also suggested the presence of a nonsporulating latent rust infection on the same kudzu leaflet at the margin on the opposite side of the midrib. Soybean rust first was confirmed on soybean in Illinois in 2006 (3), but to our knowledge, this is the first observation of the disease on kudzu in the state. This report confirms that at least some kudzu plants in Illinois are susceptible to soybean rust and that latent kudzu infection may exist without outward signs of the fungus. Currently, this is the most northern observation of soybean rust on kudzu in North America. It is unknown what role, if any, Illinois kudzu will play in the epidemiology of soybean rust in the state. Since kudzu tops die after the first frost, there is no expectation of P. pachyrhizi to overwinter in Illinois on kudzu as it does in some states adjacent to the Gulf of Mexico. References: (1) R. D. Frederick et al. Phytopathology 92:217, 2002. (2) P. F. Harmon et al. Online publication. doi:10.1094/PHP-2005-0613-01-RS. Plant Health Progress, 2005. (3) G. L. Hartman et al. Plant Dis. 91:466, 2007. (4) R. W. Schneider et al. Plant Dis. 89:774, 2005.


2009 ◽  
Vol 10 (1) ◽  
pp. 23 ◽  
Author(s):  
Edward J. Sikora ◽  
Dennis P. Delaney ◽  
Mary A. Delaney ◽  
Kathy S. Lawrence ◽  
Malcomb Pegues

Soybean rust (SBR), caused by the fungus Phakopsora pachyrhiza, has been a recurring problem for soybean growers in the southern United States. In some cases, growers in this region have followed a fungicide spray program consisting of two fungicide applications to protect their crop from the disease. Our study was conducted to determine how various sequential fungicide spray programs perform under the relatively high SBR pressure found in Alabama. Results from this study suggest that there are significant differences in the relative effectiveness of a program based on products used and the sequence in which they are applied. Factors such as recent weather conditions, proximity to sources of SBR, cost of available products, and an estimate of a crops yield potential should be considered when choosing a fungicide program. Accepted for publication 10 February 2009. Published 2 April 2009.


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