|
|
| |
| |
First Asian soybean rust found in Republic of Congo
|
9/17/2007 11:40 a.m. CDT -- Asian soybean rust has been confirmed for the first time in the Democratic Republic of Congo, on soybeans in February.
Nigeria and Uganda are the closest countries where soybean rust had been found before.
In February 2007, during a disease survey in DRC, soybean leaves with rust symptoms were observed in 10 fields in the following areas in Bas Congo Province: Bangu, Kimpese, Kolo-Fuma, Lukala, Mbanza-Ngungu, Mpalukide, Mvuazi, and Ntemo. Rust incidence in these fields ranged from 85 percent to 100 percent, while severity ranged between 3 percent and 35 percent of the leaf area on infected plants.
Urediniospores were transparent, minutely echinulate (set with small spines), and measured 23 to 31 micrometers by 16 to 20 micrometers. Within a week of collection, infected leaf samples were sent to the USDA-Agricultural Research Service Foreign Disease-Weed Science Research Unit for pathogen identification. DNA was extracted from sections of leaves containing sori, and all 10 field samples amplified in a real-time fluorescent PCR with Phakopsora pachyrhizi-specific primers.
Infected leaves of cultivar Vuangi collected from one field each in the INERA [Institut de l'Environnement et Recherches Agricoles] Research Station, Kimpese-Crawford, and Kimpese-Ceco were separately washed in sterile water to collect urediniospores that were used to separately inoculate three detached leaves of susceptible cultivar TGx 1485-1D.
Lesions on inoculated leaves developed five days after inoculation (DAI), and pustules (110 to 130 micrometers) formed 7 DAI and erupted two days later, exuding columns of urediniospores similar in size to the initially collected isolates. Inoculation of another set of detached leaves with a spore suspension from the first set of detached leaves resulted in typical rust symptoms.
Seedlings of cultivar Williams also showed typical rust symptoms when inoculated separately with urediniospores collected from nine fields (that is, all except Kimpese-Ceco, which was infective in the detached leaf assay).
Inoculation and incubation were carried out at the FDWSRU Plant Pathogen Containment Facility at Fort Detrick, Md.
The PCR assay, morphological characters of the isolates, and pathogenicity tests demonstrate that P. pachyrhizi occurs in DRC. To the researchers' knowledge, this is the first report of P. pachyrhizi infecting soybean in DRC.
Source: The American Phytopathological Society, Plant Disease 2007; 91(9): 1204.
For an easy way to stay informed, sign up for the biweekly Bulletin e-mail newsletter from www.StopSoybeanRust.com. You also will receive our RUST FLASH e-mails alerting you to important breaking news as soon as it occurs. All are archived in Bulletins.
|
| |
|
|
|
