Carson M L
Research Plant Pathologist and Associate Professor, USDA-ARS, Department of Plant Pathology, North Carolina State University, Raleigh 27695-7616.
Plant Dis. 1998 Sep;82(9):1043-1047. doi: 10.1094/PDIS.1998.82.9.1043.
Selection occurring during the saprophytic or overwintering phase of the life cycle of Cochliobolus heterostrophus, the causal agent of southern leaf blight of maize, may be a factor in the persistence of apparently less aggressive isolates in the pathogen population. The relative aggressiveness and ability to perennate of 22 isolates of C. heterostrophus from North Carolina was measured in series of experiments. Significant differences in aggressiveness and percent perennation (overwintering survival) were observed. There was a weak but often significant negative correlation between the ability of isolates to persist on the soil surface and their aggressiveness. The ability of race O isolates to sporulate on senescent corn leaf discs was positively correlated with their aggressiveness. Selection against increased aggressiveness during overwintering does not appear sufficient by itself to counter selection for increased aggressiveness occurring during the pathogen's pathogenic phase.
玉米南方叶枯病的病原菌——异旋孢腔菌（Cochliobolus heterostrophus）在其腐生或越冬阶段发生的选择，可能是病原菌群体中明显致病性较弱的分离株得以持续存在的一个因素。在一系列实验中，对来自北卡罗来纳州的22个异旋孢腔菌分离株的相对致病性和多年生能力进行了测定。观察到致病性和多年生百分比（越冬存活率）存在显著差异。分离株在土壤表面存活的能力与其致病性之间存在微弱但通常显著的负相关。O小种分离株在衰老玉米叶片圆盘上产孢的能力与其致病性呈正相关。仅靠越冬期间对致病性增强的选择似乎不足以抵消病原菌致病阶段对致病性增强的选择。
