Swett Cassandra L, Kirkpatrick Sharon C, Gordon Thomas R
Department of Plant Science and Landscape Architecture, University of Maryland, College Park 20742.
Department of Plant Pathology, University of California, Davis 95616.
Plant Dis. 2016 Jan;100(1):79-84. doi: 10.1094/PDIS-03-15-0270-RE. Epub 2015 Nov 12.
Fusarium circinatum can be a cause of mortality in pine seedlings but it is also possible for infected seedlings to remain symptomless. The results of this study documented a biotrophic phase in symptomless Pinus radiata seedlings that can persist for at least 52 weeks. A strain of F. circinatum, transformed to express the green fluorescent protein, was observed to grow intercellularly in the root cortex, with no evidence of damage to surrounding cells. Under experimental conditions, shoot symptoms developed only following collar infection, and root deterioration was seen only in plants that first expressed aboveground symptoms. This sequence of events implies that damage to the root system was a secondary consequence of girdling. If so, root symptoms may not reliably detect seedlings infected by F. circinatum. Supplemental mineral nutrition increased the incidence of infection and symptom development in seedlings but some infected plants remained symptomless, precluding the use of this approach to detect infected seedlings. Overall, our findings suggest that the ecological activities of F. circinatum may not be limited to a necrotrophic association with pine trees. A more comprehensive understanding of the life history of this fungus may yield insights that contribute to more effective management of pitch canker.
轮状镰刀菌可导致松树苗死亡，但受感染的树苗也可能无症状。本研究结果记录了无症状辐射松树苗中的一个活体营养阶段，该阶段可持续至少52周。观察到一株转化后表达绿色荧光蛋白的轮状镰刀菌在根皮层细胞间生长，周围细胞无损伤迹象。在实验条件下，仅在颈部感染后才出现地上部症状，且仅在首先出现地上部症状的植株中观察到根系衰退。这一系列事件表明，根系损伤是环割的次要后果。如果是这样，根部症状可能无法可靠地检测出受轮状镰刀菌感染的树苗。补充矿质营养增加了树苗感染和症状出现的发生率，但一些受感染植株仍无症状，这排除了使用这种方法检测受感染树苗的可能性。总体而言，我们的研究结果表明，轮状镰刀菌的生态活动可能不限于与松树的坏死营养关联。对这种真菌生活史的更全面了解可能会产生有助于更有效管理松材线虫病的见解。
