du Preez E D, van Rij N C, Lawrance K F, Miles M R, Frederick R D
KwaZulu-Natal Department of Agriculture and Environmental Affairs, Private Bag X9059, Pietermaritzburg 3200, South Africa.
USDA ARS, National Soybean Research Center, University of Illinois, Urbana 61801.
Plant Dis. 2005 Feb;89(2):206. doi: 10.1094/PD-89-0206C.
During April 2004, a 150-m dry bean (Phaseolus vulgaris) plot growing adjacent to rust-infected soybean (Glycine max) at Cedara Agricultural Research Farm (29°32'S 30°16'E) was observed to be infected with two distinct rust types. Common bean rust (caused by Uromyces appendiculatus) with reddish brown uredinia and black telia was readily identified. A second rust with smaller sporulating uredinia (1.0 to 1.5 mm), which were gray in appearance, was also found. Visual rust severity on the dry bean plants, which were in mid pod-fill, was high (approximately 30 to 40% disease incidence). Twenty plants were examined and observed to be infected with both rusts. With microscopic examination of no fewer than 20 leaves per plant, the urediniospores from the smaller lesions were determined to be morphologically similar to Phakopsora pachyrhizi (3). Real-time fluorescent polymerase chain reaction assays on six leaves and sequence analysis of the nuclear ribosomal internal transcribed spacer region 2 (1) verified the identity of the urediniospores as P. pachyrhizi. Although P. vulgaris is a known host of P. pachyrhizi, to our knowledge this is the first time since the arrival of soybean rust in 2001 that P. pachyrhizi has been observed on an alternate host plant in South Africa (2). Since dry beans are grown all year in frost-free areas, the implications are that dry beans may serve as an important overwintering host and source of inoculum for seasonal soybean rust outbreaks. References: (1) R. D. Frederick et al. Phytopathology 92:217, 2002. (2) Z. A. Pretorius et al. Plant Dis. 85:1288, 2001. (3) J. B. Sinclair and G. L. Hartman. Soybean Rust. Pages 25-26 in: Compendium of Soybean Diseases, 4th ed. G. L. Hartman et al. eds. The American Phytopathological Society, St. Paul, MN, 1999.
2004年4月期间，在塞达拉农业研究农场（南纬29°32′，东经30°16′），一块与感染锈病的大豆（大豆属）相邻种植的150米长的干豆（菜豆属）地块被观察到感染了两种不同类型的锈病。由疣顶单胞锈菌引起的普通菜豆锈病很容易识别，其夏孢子堆呈红棕色，冬孢子堆呈黑色。还发现了另一种锈病，其产孢夏孢子堆较小（1.0至1.5毫米），外观呈灰色。处于豆荚充实中期的干豆植株上锈病的目测严重程度很高（发病率约为30%至40%）。检查了20株植株，发现它们都感染了这两种锈病。通过对每株植株不少于20片叶子进行显微镜检查，确定较小病斑上的夏孢子在形态上与大豆锈菌相似（3）。对六片叶子进行实时荧光聚合酶链反应分析以及对核糖体核糖核酸内转录间隔区2进行序列分析（1），证实了夏孢子为大豆锈菌。虽然菜豆是大豆锈菌已知的寄主，但据我们所知，这是自2001年大豆锈病传入以来，首次在南非的替代寄主植物上观察到大豆锈菌（2）。由于干豆在无霜地区全年种植，这意味着干豆可能成为季节性大豆锈病爆发的重要越冬寄主和接种体来源。参考文献：（1）R. D. Frederick等人，《植物病理学》92:217，2002年。（2）Z. A. Pretorius等人，《植物病害》85:1288，2001年。（3）J. B. Sinclair和G. L. Hartman，《大豆锈病》，载于《大豆病害简编》第4版，G. L. Hartman等人编，美国植物病理学会，明尼苏达州圣保罗，1999年，第25 - 26页。
