Viji G, Wu B, Kang S, Uddin W, Huff D R
Department of Plant Pathology, The Pennsylvania State University, PA 6802.
Department of Agronomy, The Pennsylvania State University, PA 16802.
Plant Dis. 2001 Aug;85(8):817-826. doi: 10.1094/PDIS.2001.85.8.817.
Gray leaf spot is a serious disease of perennial ryegrass (Lolium perenne) turf in the United States. Isolates of Pyricularia grisea causing the disease in perennial ryegrass were characterized using molecular markers and pathogenicity assays on various gramineous hosts. Genetic relationships among perennial ryegrass isolates were determined using different types of trans-posons as probes. Phylogenetic analysis using Pot2 and MGR586 probes, analyzed with AMOVA (analysis of molecular variance), showed that these isolates from perennial ryegrass consist of three closely related lineages. All the isolates belonged to a single mating type, MAT1-2. Among 20 isolates from 16 host species other than perennial ryegrass, only the isolates from wheat (Triticum aestivum) and triticale (× Triticosecale), showed notable similarity to the perennial ryegrass isolates based on their Pot2 fingerprints. The copy number and fingerprints of Pot2 and MGR586 in isolates of P. grisea from perennial ryegrass indicate that they are genetically distinct from the isolates derived from rice (Oryza sativa) in the United States. The perennial ryegrass isolates also had the same sequence in the internal transcribed spacer (ITS) region of the genes encoding ribosomal RNA as that of the wheat and triticale isolates, and exhibited rice isolate sequence polymorphisms. In pathogenicity assays, all the isolates of P. grisea from Legacy II perennial ryegrass caused characteristic blast symptoms on Marilee soft white winter wheat, Bennett hard red winter wheat, Era soft white spring wheat, and Presto triticale, and they were highly virulent on these hosts. An isolate from wheat and one from triticale (from Brazil) were also highly virulent on perennial ryegrass and Rebel III tall fescue (Festuca arundinacea). None of the isolates from perennial ryegrass caused the disease on Lagrue rice, and vice versa. Understanding the population structure of P. grisea isolates infecting perennial ryegrass and their relatedness to isolates from other gramineous hosts may aid in identifying alternate hosts for this pathogen.
灰斑病是美国多年生黑麦草（Lolium perenne）草坪的一种严重病害。利用分子标记和对各种禾本科寄主的致病性测定，对引起多年生黑麦草病害的稻瘟病菌株进行了特征分析。使用不同类型的转座子作为探针，确定了多年生黑麦草分离株之间的遗传关系。使用Pot2和MGR586探针进行系统发育分析，并通过分子方差分析（AMOVA）表明，这些来自多年生黑麦草的分离株由三个密切相关的谱系组成。所有分离株都属于单一交配型MAT1-2。在来自多年生黑麦草以外的16个寄主物种的20个分离株中，只有来自小麦（Triticum aestivum）和小黑麦（× Triticosecale）的分离株，基于其Pot2指纹图谱，与多年生黑麦草分离株表现出显著相似性。多年生黑麦草稻瘟病菌株中Pot2和MGR586的拷贝数和指纹图谱表明，它们在遗传上与美国水稻（Oryza sativa）来源的分离株不同。多年生黑麦草分离株在编码核糖体RNA的基因的内部转录间隔区（ITS）区域也具有与小麦和小黑麦分离株相同的序列，并表现出水稻分离株的序列多态性。在致病性测定中，来自Legacy II多年生黑麦草的所有稻瘟病菌株在Marilee软质白冬小麦、Bennett硬质红冬小麦、Era软质白春小麦和Presto小黑麦上引起典型的稻瘟病症状，并且它们对这些寄主具有高致病性。来自小麦的一个分离株和来自小黑麦（来自巴西）的一个分离株对多年生黑麦草和Rebel III高羊茅（Festuca arundinacea）也具有高致病性。来自多年生黑麦草的分离株均未在Lagrue水稻上引起病害，反之亦然。了解感染多年生黑麦草的稻瘟病菌株的种群结构及其与其他禾本科寄主分离株的相关性，可能有助于确定该病原菌的替代寄主。
