Isakeit T, Jo Y
Department of Plant Pathology and Microbiology, Texas A&M University, College Station 77843.
Plant Dis. 2008 Sep;92(9):1369. doi: 10.1094/PDIS-92-9-1369C.
The first discovery of Asian soybean rust (ASR) caused by Phakopsora pachyrhizi H. Sydow & Sydow in the continental United States was in Louisiana in 2004 (3). In Texas, the uredial stage of this fungus was first found on kudzu (Pueraria lobata) in November 2005 and 3 months later on soybean (Glycine max) (2). The telial stage of P. pachyrhizi was first reported in the continental United States on kudzu in central Florida (1). On January 5, 2008, telia of P. pachyrhizi along with uredia were found on living kudzu leaves at two locations in Polk and Liberty counties of East Texas, where only the uredial stage had been found in September of 2007. The kudzu in both locations had died back more than 99% in January. A single telium or a cluster of telia were found along with uredinia on the abaxial leaf surface. Telia and uredinia (n = 20) were similar in size, 136.3 ± 26.3 and 133.1 ± 16.4 μm in diameter, respectively. Telia were dark brown to black compared with tan colored uredinia. Elongated, oval-shaped teliospores (n = 15) were 18.1 ± 1.7 μm long and 10.6 ± 1.0 μm wide. A reexamination of herbarium specimens from previous ASR collections indicated that telia had been present on kudzu leaves from Liberty County collected in December of 2005 and 2006. In contrast, telia were not found on soybean leaves collected in February of 2006 and 2007 and January of 2008 from Hidalgo County in the Lower Rio Grande Valley (LRGV), an area with a subtropical climate where ASR hosts could survive year round. Kudzu does not occur in the LRGV. Infected kudzu in East Texas can support production of telia over the winter months. However, the hosts that can be infected by basidiospores have not been identified, and so the significance of telia as a source of genetic variation is not known. To our knowledge, this is the first report of the telial stage of P. pachyrhizi in Texas. References: (1) C. L. Harmon et al. Plant Dis. 90:380, 2006. (2) T. Isakeit et al. Plant Dis. 90:971, 2006. (3) R. W. Schneider et al. Plant Dis. 89:774, 2005.
2004年在美国大陆首次发现由豆薯层锈菌（Phakopsora pachyrhizi H. Sydow & Sydow）引起的亚洲大豆锈病（ASR），地点在路易斯安那州（3）。在得克萨斯州，2005年11月首次在葛藤（Pueraria lobata）上发现这种真菌的夏孢子堆阶段，3个月后在大豆（Glycine max）上发现（2）。豆薯层锈菌的冬孢子堆阶段首次在美国大陆佛罗里达州中部的葛藤上被报道（1）。2008年1月5日，在得克萨斯州东部波尔克县和利伯蒂县的两个地点，在活的葛藤叶片上发现了豆薯层锈菌的冬孢子堆以及夏孢子堆，而在2007年9月仅发现了夏孢子堆阶段。1月份，这两个地点的葛藤死亡超过99%。在叶片背面发现单个冬孢子堆或一堆冬孢子堆以及夏孢子堆。冬孢子堆和夏孢子堆（n = 20）大小相似，直径分别为136.3±26.3微米和133.1±16.4微米。与黄褐色的夏孢子堆相比，冬孢子堆为深褐色至黑色。细长的椭圆形冬孢子（n = 15）长18.1±1.7微米，宽10.6±1.0微米。对之前亚洲大豆锈病收集的标本馆标本重新检查表明，2005年12月和2006年从利伯蒂县收集的葛藤叶片上存在冬孢子堆。相比之下，在2006年2月、2007年以及2008年1月从下里奥格兰德河谷（LRGV）伊达尔戈县收集的大豆叶片上未发现冬孢子堆，该地区为亚热带气候，亚洲大豆锈病寄主可终年存活。LRGV地区没有葛藤。得克萨斯州东部受感染的葛藤能够在冬季支持冬孢子堆的产生。然而，尚未确定可被担孢子感染的寄主，因此冬孢子堆作为遗传变异来源的意义尚不清楚。据我们所知，这是得克萨斯州首次报道豆薯层锈菌的冬孢子堆阶段。参考文献：（1）C. L. Harmon等人，《植物病害》90:380，2006年。（2）T. Isakeit等人，《植物病害》90:971，2006年。（3）R. W. Schneider等人，《植物病害》89:774，2005年。
