Pretorius Z A, Visser B, du Preez P J
Department of Plant Sciences, University of the Free State, Bloemfontein 9300, South Africa.
Plant Dis. 2007 Oct;91(10):1364. doi: 10.1094/PDIS-91-10-1364C.
Asian soybean rust was first reported on soybean in South Africa (SA) in 2001 (3). The disease has occurred in all ensuing seasons, particularly in the humid, eastern production regions, causing significant losses in soybean fields not protected by fungicides. In April 2005, rust-infected Pueraria lobata (kudzu) was detected near Nelspruit, Mpumalanga, SA. At this location (25°20'41″S, 30°43'30″E), kudzu plants occurred abundantly on road sides, edges of pine plantations, and in natural vegetation. Most vines were infected, with abaxial surfaces of older leaves often showing 100% severity. Following inoculation with rust spores collected from kudzu, soybean line PI200492 (Rpp1) produced tan lesions typical of a susceptible reaction for Asian soybean rust. PI230970 (Rpp2), PI462312 (Rpp3), and PI459025 (Rpp4) showed red-brown lesions typical of a resistant reaction. Using Ppm1/Ppa2 and Ppm1/Ppm2 primer combinations, the amplification profiles of the internal transcribed spacer region (1) of rust DNA extracted from primary leaves of line PI200492 infected with spores collected from kudzu positively identified the pathogen as Phakopsora pachyrhizi. The Ppm1/Pme2 primer combination specific for P. meibomiae (1) did not yield an amplification product. The Qualiplate ELISA test kit (EnviroLogix Inc., Portland, ME) verified the identification of P. pachyrhizi on an original kudzu sample as well as the leaf material used for DNA analysis. A survey of kudzu at the Nelspruit site during July 2005 confirmed the presence of the pathogen during the offseason for soybean. At that time, incidence of kudzu rust remained high, but few leaves showed high severity. The susceptibility of kudzu to Asian soybean rust has been reported in controlled infection studies in SA (2). To our knowledge, this is the first report of P. pachyrhizi causing rust on a large, naturally occurring kudzu population in SA. References: (1) R. D. Frederick et al. Phytopathology 92:217, 2002. (2) A. Nunkumar. M.Sc. thesis. University of KwaZulu-Natal, South Africa, 2006. (3) Z. A. Pretorius et al. Plant Dis. 85:1288, 2001.
2001年，亚洲大豆锈病首次在南非被报道于大豆作物上（3）。在随后的所有季节该病均有发生，尤其在潮湿的东部产区，导致未使用杀真菌剂保护的大豆田遭受重大损失。2005年4月，在南非姆普马兰加省内尔斯普雷特附近检测到感染锈病的野葛。在这个地点（南纬25°20'41″，东经30°43'30″），路边、松树林边缘和自然植被中野葛生长繁茂。大多数藤蔓都受到感染，老叶的背面常常呈现100%的严重度。用从野葛上采集的锈病孢子接种后，大豆品系PI200492（Rpp1）产生了典型的黄褐色病斑，这是亚洲大豆锈病易感反应的表现。PI230970（Rpp2）、PI462312（Rpp3）和PI459025（Rpp4）则呈现出典型的抗反应红褐色病斑。使用Ppm1/Ppa2和Ppm1/Ppm2引物组合，对从感染了从野葛采集的孢子的PI200492品系初生叶中提取的锈病DNA的内部转录间隔区（1）进行扩增分析，明确鉴定出病原体为大豆锈菌。针对美孢层锈菌（1）的特异性Ppm1/Pme2引物组合未产生扩增产物。Qualiplate ELISA检测试剂盒（EnviroLogix公司，缅因州波特兰）验证了在原始野葛样本以及用于DNA分析的叶片材料上对大豆锈菌的鉴定。2005年7月对内尔斯普雷特地点的野葛进行的调查证实，在大豆的非生长季节病原体依然存在。当时，野葛锈病的发病率仍然很高，但很少有叶片呈现高严重度。在南非进行的受控感染研究中已报道了野葛对亚洲大豆锈病的易感性（2）。据我们所知，这是关于大豆锈菌在南非一大片自然生长的野葛种群上引发锈病的首次报道。参考文献：（1）R. D. Frederick等人，《植物病理学》92:217，2002年。（2）A. Nunkumar，硕士论文，南非夸祖鲁 - 纳塔尔大学，2006年。（3）Z. A. Pretorius等人，《植物病害》85:1288，2001年。
