Azad H R, Holmes G J, Cooksey D A
Research Associate, Department of Plant Pathology, University of California, Riverside 92521.
Extension Plant Pathologist, Department of Plant Pathology, North Carolina State University, Raleigh 27695.
Plant Dis. 2000 Sep;84(9):973-979. doi: 10.1094/PDIS.2000.84.9.973.
An unreported disease of sudangrass (Sorghum sudanense) was observed in commercial fields in Imperial Valley of California. Symptoms included light-colored necrotic streaks, and white or tan irregular blotches, often associated with reddish purple to dark brown margins. Pantoea ananas was consistently isolated from the blotches with reddish margins, while Pantoea stewartii or mixtures of both species were isolated from necrotic streaks without reddish margins. Fourteen seed samples harvested in different locations were assayed and found to be 0.0 to 3.6% infested with P. ananas. Seed transmission may be a means by which the pathogen is introduced. Symptoms in inoculated plants appeared as early as 2 and as late as 20 days after inoculation, depending on the inoculum level, methods of inoculation, temperature, and available moisture. The initial symptoms caused by inoculations with both bacteria were similar, but as symptoms progressed, P. ananas was associated with white streaks or irregular necrotic blotches often surrounded by a reddish or purplish hue. P. stewartii was associated with light-colored necrotic streaks. A synergistic or antagonistic relationship was not observed between the two pathogens in co-inoculations. In host range studies, both bacteria caused disease on sorghum and sudangrass at similar levels of severity. P. ananas was also pathogenic on corn and oat. P. stewartii from sudangrass was pathogenic on corn but did not cause wilting that was observed with Stewart's wilt strains of P. stewartii from corn. The sudangrass strains of P. stewartii also infected oat and triticale, while the Stewart's wilt strains did not. Both P. ananas and P. stewartii from sudangrass grew at relatively high temperatures (43 and 37°C, respectively) and caused disease at elevated temperatures and conditions of relative humidity similar to those in the Imperial Valley during late summer when epidemics of the disease were common.
在加利福尼亚州帝王谷的商业田地里观察到一种未报道过的苏丹草（高粱属苏丹草）病害。症状包括浅色坏死条纹以及白色或棕褐色不规则斑块，这些斑块通常伴有红紫色至深褐色边缘。边缘带红色的斑块中始终能分离出菠萝泛菌，而边缘无红色的坏死条纹中分离出斯图尔特泛菌或两种菌的混合菌。对在不同地点收获的14个种子样本进行检测，发现菠萝泛菌的侵染率为0.0%至3.6%。种子传播可能是病原菌传入的一种途径。接种植株的症状最早在接种后2天出现，最晚在20天出现，这取决于接种菌浓度、接种方法、温度和有效湿度。两种细菌接种引起的初始症状相似，但随着症状发展，菠萝泛菌与白色条纹或不规则坏死斑块相关，这些斑块常被红色或紫色环绕。斯图尔特泛菌与浅色坏死条纹相关。在共接种时未观察到两种病原菌之间存在协同或拮抗关系。在寄主范围研究中，两种细菌在高粱和苏丹草上引起病害的严重程度相似。菠萝泛菌对玉米和燕麦也有致病性。来自苏丹草的斯图尔特泛菌对玉米有致病性，但不会像来自玉米的斯图尔特枯萎病菌株那样引起萎蔫。苏丹草的斯图尔特泛菌菌株也能感染燕麦和小黑麦，而斯图尔特枯萎病菌株则不能。来自苏丹草的菠萝泛菌和斯图尔特泛菌在相对较高温度下（分别为43℃和37℃）均能生长，并在高温及与夏末帝王谷相似的相对湿度条件下引发病害，此时该病流行较为常见。
