Submitted to: Canadian Journal of Plant Pathology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 6/13/2005
Publication Date: 10/8/2005
Citation: Strausbaugh, C.A., Overturf, K.E., Koehn, A.C. 2005. Pathogenicity and real-time pcr detection of fusarium spp. in wheat and barley roots. Canadian Journal of Plant Pathology. 27:430-438. Interpretive Summary: Fusarium root rot of wheat is a fungal root disease problem of concern worldwide. The primary causal agent in southeastern Idaho is Fusarium culmorum. Traditionally soil-borne pathogens have been managed through the use of crop rotations, proper fertilization, tillage, and host resistance. However, crop rotation options are limited in some areas because of low rainfall. Also, in an effort to minimize production inputs and reduce soil and wind erosion there is a trend toward direct-seeded cereal production. These cropping challenges along with the lack of commercial cultivars with resistance to Fusarium root and foot rot makes controlling this disease complex problematic. Above ground symptoms of Fusarium root and foot rot include missing and stunted plants and/or the development of “white heads.” However, these symptoms may not always appear and Fusarium root and foot rot may go unnoticed unless roots are examined. Root examination is laborious and difficult since lesions caused by F. culmorum and F. pseudograminearum can be confused with those caused by other Fusarium spp. and Biopolaris sorokiniana. In this study we established a molecular assay that will allow researchers to quantify F. culmorum in wheat and barley roots. This assay should allow for more sensitive root disease research with the Fusarium root rot complex and aid in the development of resistant cultivars. The study also established that some Fusarium spp. considered to be saprophytes or minor pathogens can significantly reduce root length even though they produce what appear to be insignificant lesions on the roots. If these so called “minor pathogens” significantly restrict root growth in our drier rainfed cereal production areas, they are likely to negatively impact production.
Technical Abstract: The influence of Fusarium spp. frequently isolated from wheat and barley roots in southern Idaho was investigated along with the development of a real-time PCR assay. Four growth chamber experiments and two field studies were conducted to establish the virulence of five Fusarium spp. on wheat and barley roots. Root material from these studies was then utilized to establish a real-time PCR assay based on nucleotide sequences for the tri5 gene. Fusarium culmorum followed by F. acuminatum and F. reticulatum resulted in the largest root lesions and percent infected root area. However, the greatest impact on total root length was by F. semitectum followed by F. acuminatum and F. equiseti. The TaqMan based real-time assay was able to quantify F. culmorum in root tissue from both growth chamber and field studies down to 61 pg. The assay will also detect F. pseudograminearum and F. graminearum.