Applying real-time quantitative PCR to fusarium crown rot of wheat

Fusarium crown rot (FCR) of wheat is a persistent problem that causes significant losses worldwide. In Montana, FCR is caused primarily by Fusarium culmorum and F pseudograminearum. Recently, a real-time quantitative PCR (QPCR) assay was developed for FCR using primers and probes specific for a segment of the trichodiene synthase (tri5) gene. The purpose of this study was to determine the utility of QPCR for accessing FCR severity on wheat in field experiments. In 2004 and 2005, plots of spring and durum wheat were inoculated with varying levels of F pseudograminearum oat inoculum and grown under rain-fed conditions. Two weeks prior to harvest, plants were collected from the plots and assessed for FCR severity and analyzed by QPCR for Fusarium DNA quantities. Disease severity scores (DSS) and Fusarium DNA quantities were positively correlated with each other for all three cultivars in 2004 but for only the durum cultivar in 2005 (P < 0.05). In 2004, grain yields for both spring wheat cultivars were negatively correlated with Fusarium DNA quantities (P > 0.05). When DSS and Fusarium DNA quantities negatively correlated with yield, both measurements were comparable in predicting yield reduction (R = -0.64 and -0.77, respectively). Results indicate that this QPCR assay is effective in measuring FCR severity in wheat.