Bradley C A, Río L E Del
Department of Plant Pathology, North Dakota State University, Fargo, ND 58105.
Plant Dis. 2003 May;87(5):601. doi: 10.1094/PDIS.2003.87.5.601B.
In late August 2002, patches of soybean (Glycine max) plants in a field in Richland County, ND exhibited symptoms and signs of charcoal rot and died prematurely. Dead plants had a silvery-gray appearance, and black microsclerotia (76 ± 28 μm in diameter) were present in the vascular tissue of the lower stems and roots. Stem tissue was placed in petri dishes containing potato dextrose agar (PDA). Gray hyphae grew from the stem tissue and subsequently turned black and formed microsclerotia (188 × 139 ± 48 μm). The fungus was identified as Macrophomina phaseolina (Tassi) Goid. based on colony color and morphology and size of the microsclerotia (1). To confirm pathogenicity, soybean plants (cv. Garst D 041 RR) were grown in the greenhouse and inoculated with the previously obtained isolate of M. phaseolina. Stems of soybean plants at the V2 stage were excised just below the third node. Mycelia plugs of a 1-week-old culture of M. phaseolina were placed into the large end of disposable micropipette tips (200 μl). The micropipette tips containing the M. phaseolina culture were subsequently placed over 10 excised soybean stems. To serve as a control, 10 excised soybean stems were inoculated with micropipette tips containing plugs of noninfested PDA. Thirty days after inoculation, micropipette tips were removed, and lesions that had developed on the stem were measured. The mean lesion length of M. phaseolina inoculated stems was 7 mm; no lesions developed on the control plants. M. phaseolina was reisolated from infected tissue of inoculated plants that were placed on PDA. Charcoal rot was only observed in the Richland County field; however, no surveys were conducted to determine the prevalence of the disease throughout the soybean production area of North Dakota. Because it is now known that this disease occurs in North Dakota, growers, extension personnel, and crop consultants must scout for the disease and practice recommended management strategies. Reference: (1) G. S. Smith and T. D. Wyllie. Charcoal rot. Pages 29-31 in: Compendium of Soybean Diseases, 4th ed. G. L. Hartman, J. B. Sinclair, and J. C. Rupe, eds. The American Phytopathological Society, St. Paul, MN, 1999.
2002年8月下旬，北达科他州里奇兰县一块田地里的大豆（Glycine max）植株出现了炭腐病的症状和病征，并过早死亡。死亡植株呈现银灰色外观，黑色微菌核（直径76±28μm）存在于下部茎和根的维管组织中。将茎组织置于含有马铃薯葡萄糖琼脂（PDA）的培养皿中。灰色菌丝从茎组织中生长出来，随后变黑并形成微菌核（188×139±48μm）。根据菌落颜色、形态以及微菌核的大小，该真菌被鉴定为菜豆壳球孢（Macrophomina phaseolina (Tassi) Goid.）（1）。为了确认致病性，在温室中种植大豆植株（品种为Garst D 041 RR），并用先前获得的菜豆壳球孢分离株进行接种。在V2生长阶段的大豆植株，在第三节下方切除茎部。将菜豆壳球孢1周龄培养物的菌丝体小块放入一次性微量移液器吸头（200μl）的大口端。随后将含有菜豆壳球孢培养物的微量移液器吸头放置在10个切除的大豆茎上。作为对照，用含有未感染PDA小块的微量移液器吸头接种10个切除的大豆茎。接种30天后，移除微量移液器吸头，并测量茎上形成的病斑。接种菜豆壳球孢的茎的平均病斑长度为7mm；对照植株上未形成病斑。从接种植株的感染组织中重新分离出菜豆壳球孢，并将其置于PDA上。仅在里奇兰县的田地里观察到炭腐病；然而，未进行调查以确定北达科他州大豆产区该病的流行情况。由于现在已知这种病害在北达科他州发生，种植者、推广人员和作物顾问必须对该病进行巡查，并实施推荐的管理策略。参考文献：（1）G. S. 史密斯和T. D. 威利。炭腐病。载于：《大豆病害简编》第4版，G. L. 哈特曼、J. B. 辛克莱和J. C. 鲁普编。美国植物病理学会，明尼苏达州圣保罗，1999年，第29 - 31页。
