Isakeit T, Odvody G N, Shelby R A
Department of Plant Pathology and Microbiology, Texas A&M University, Weslaco 78596.
Department of Plant Pathology and Microbiology, Texas A&M University, Corpus Christi 78406.
Plant Dis. 1998 May;82(5):592. doi: 10.1094/PDIS.1998.82.5.592A.
In March 1997, ergot was found on sorghum (Sorghum bicolor (L.) Moench) regrowth in several abandoned commercial grain sorghum fields in Cameron and Hidalgo counties in the Lower Rio Grande Valley (LRGV) of Texas. White sphacelia in florets produced honeydew containing macrospores (hyaline, oblong to oval, 10 to 25 μm × 5 to 7 μm) and microspores (hyaline, spherical, 3 μm in diameter). Macrospores germinated iteratively to form secondary conidia when placed on water agar and in situ following rain. Secondary conidia were hyaline, pyriform, with a protruding hilum, and measured 10 to 17 μm × 5 to 7 μm. High-pressure liquid chromatography analysis detected the alkaloid di-hydroergosine in sphacelia, which is unique to C. africana (1). The pathogen was also confirmed on adjacent johnsongrass (S. halepense). The spread of ergot across Texas was associated with the progressive maturation of the commercial sorghum crop as follows: LRGV (mid-May), Coastal Bend near Corpus Christi (June), Winter Garden area southwest of San Antonio (July), and the seed production region of the Texas Panhandle (mid-August). Ergot incidence ranged from a trace to 10% of the heads in (self-fertile) grain sorghum fields of the LRGV. Most heads had only a few infected florets, but a few heads had 35 to 50% of the florets infected. Only trace amounts were found in grain sorghum fields in other areas of the state. Incidence and severity of ergot were greatest in fields of male-sterile sorghums grown for forage. Ergot was generally low in primary heads of male-sterile sorghums in hybrid seed production fields but, in the absence of pollen, axillary tillers sometimes developed high levels of ergot. The major impact of sorghum ergot is expected to be in hybrid seed production fields in the High Plains of Texas. Reference: (1) D. E. Frederickson et al. Mycol. Res. 95:1101, 1991.
1997年3月，在得克萨斯州下里奥格兰德河谷（LRGV）卡梅伦县和伊达尔戈县的几个废弃商业谷物高粱田中的高粱（Sorghum bicolor (L.) Moench）再生植株上发现了麦角菌。小花上的白色粉孢产生的蜜露含有大孢子（透明，长椭圆形至椭圆形，10至25μm×5至7μm）和小孢子（透明，球形，直径3μm）。将大孢子置于水琼脂上以及雨后原位培养时，会反复萌发形成次生分生孢子。次生分生孢子透明，梨形，具突出脐点，大小为10至17μm×5至7μm。高压液相色谱分析在粉孢中检测到生物碱二氢麦角异胺，这是非洲麦角菌（Claviceps africana）所特有的（1）。在相邻的约翰逊草（S. halepense）上也证实了该病原菌。麦角菌在得克萨斯州的传播与商业高粱作物的逐渐成熟有关，情况如下：LRGV（5月中旬）、科珀斯克里斯蒂附近的海岸弯地区（6月）、圣安东尼奥西南部的冬季花园地区（7月）以及得克萨斯州狭长地带的种子生产区（8月中旬）。在LRGV的（自花授粉）谷物高粱田中，麦角菌发病率在穗头中从微量到10%不等。大多数穗头只有少数小花感染，但少数穗头有35%至50%的小花感染。在该州其他地区的谷物高粱田中仅发现微量麦角菌。在用作饲料的雄性不育高粱田中，麦角菌的发病率和严重程度最高。在杂交种子生产田中，雄性不育高粱的主穗上麦角菌通常较少，但在没有花粉的情况下，腋生分蘖有时会出现高水平的麦角菌。预计高粱麦角菌的主要影响将出现在得克萨斯州高平原的杂交种子生产田中。参考文献：（1）D. E. Frederickson等人。《真菌学研究》95:1101，1991年。
