Fusarium culmorum (Fc) and F. graminearum (Fg) belong to the predominant causal agents of fusarium crown and root rot (FCR) in wheat. While many studies have been done to investigate crown rot, including stem base infection, root colonization and mycotoxin production associated with root rot is not well understood. In this study the impact of mycotoxins on the colonization of wheat roots and stem bases was analysed by using Fc and Fg isolates that varied in both quantity and types of trichothecenes they produce. Seedling inoculations in growth chambers with a high deoxynivalenol (DON)- and 3-acetyldeoxynivalenol (3ADON)-producing isolate led to more severe symptoms and 20-times greater colonization of the stem base, as measured by Fc DNA accumulation, than isolates that produced less DON/3ADON. In contrast to stem base colonization, in vitro inoculations of roots with a Tri5 deletion mutant deficient in Fg trichothecene production led to three-times higher colonization than the wildtype. Furthermore, an Fc isolate that produced low levels of zearalenone resulted in twice the level of colonization of a high DON/3ADON-producing isolate included in the study. When root inoculation with a low DON/3ADON-producing Fc isolate was supplemented with exogenous DON, DON production decreased by more than half per unit weight of Fc DNA, and root colonization doubled compared to the untreated control. Therefore, in contrast to its potential role as an aggressiveness factor in stem base infection, trichothecene production by Fc and Fg is detrimental to the early stages of wheat root colonization in FCR.
Bibliographical noteFunding Information:
The authors are grateful for the support of a postdoctoral fellowship for M. Winter from the German Research Association (DFG). They would like to thank H. C. Kistler and K. Broz, Cereal Disease Laboratory, USDA ARS, St Paul, MN, USA for providing strains of F. graminearum and providing laboratory space as well as guidance during the work with the mutant strain of F. graminearum and for critical discussions. Additionally, they thank S. P. McCormick, USDA ARS NCAUR, Peoria, IL, USA for providing pure deoxynivalenol.
© 2018 British Society for Plant Pathology
Copyright 2019 Elsevier B.V., All rights reserved.
- aggressiveness factor
- deoxynivalenol (DON)
- fusarium foot and root rot
- soilborne diseases