Department of Biology, University of Virginia, Charlottesville, VA, 22904, USA.
Biology Department, Amherst College, Amherst, MA, 01003, USA.
Am J Bot. 2018 Jun;105(6):1088-1095. doi: 10.1002/ajb2.1114. Epub 2018 Jul 11.
Plant pathogens that form persistent systemic infections within plants have the potential to affect multiple plant life history traits, yet we tend to focus only on visible symptoms. Anther smut of Silene latifolia caused by the fungus Microbotryum lychnidis-dioicae induces the anthers of its host to support fungal spore production instead of pollen, and the pathogen is primarily transmitted among flowering plants by pollinators. Nevertheless, most of its life cycle is spent in the asymptomatic vegetative phase, and spores falling on seedlings or nonflowering plants can also infect the host. The purpose of this study was to ask whether the fungus also had an effect on its host plant in the juvenile vegetative phase before flowering as this is important for the disease dynamics in species where infection of seedlings is commonplace.
Leaf length and leaf number of inoculated and uninoculated juvenile plants were compared in greenhouse experiments, and in one experiment, disease status of the plants at flowering was determined.
Inoculated plants had shorter but more leaves, and reduced root mass at the early juvenile (preflowering) stage. Some of these effects were detectable in plants that were inoculated but showed no disease symptoms at flowering.
These results show that pathogenic fungi can have endophyte-like effects even in the total absence of their typical and more charismatic symptoms, and conversely that the assessment of endophyte effects on the fitness of their hosts should include all stages of the host life cycle.
在植物体内形成持久系统感染的植物病原体有可能影响多种植物生活史特征，但我们往往只关注可见的症状。丝石竹由真菌 Microbotryum lychnidis-dioicae 引起的花药黑粉病会促使其宿主的花药支持真菌孢子的产生而不是花粉，并且病原体主要通过传粉媒介在开花植物之间传播。然而，它的大部分生命周期都处于无症状的营养阶段，落在幼苗或不开花植物上的孢子也可以感染宿主。本研究的目的是询问真菌在开花前的幼年营养阶段是否也会对其宿主植物产生影响，因为这对于感染幼苗很常见的物种中的疾病动态很重要。
在温室实验中比较了接种和未接种的幼年植物的叶片长度和叶片数量，并在一个实验中确定了植物在开花时的疾病状况。
接种植物在早期（开花前）的幼年期叶片较短但数量较多，根质量减少。在一些接种但在开花时没有表现出疾病症状的植物中可以检测到这些影响。
这些结果表明，即使在没有典型和更具魅力的症状的情况下，致病真菌也可以产生类似内生菌的作用，反之亦然，评估内生菌对其宿主适应性的影响应包括宿主生命周期的所有阶段。
