Rhizomania is one of serious threat to sugar beet production in Morocco and in several parts of the world. This disease led to a statistically significant decrease in the quality and yield of sugar beet plantations. Therefore, this study aimed at comparing the efficacy of six commonly used RNA extraction methods for the detection, recovery of RNA of beet necrotic yellow vein virus (BNYVV) and removal of amplification inhibitors by reverse transcription-polymerase chain reaction (RT-PCR). The efficiency of these extraction methods was then compared to that of a commercial isolation kit with high content of phenolic compounds. The results showed that the extraction with the lithium chloride technique, the commercial kit, and direct and membrane spotting crude extract methods were found effective in yielding a higher purity and a higher concentration of RNA when compared to the other tested methods. Extraction with the lithium chloride technique and the Qiagen kit (RNeasy Plant Mini Kit) allowed the most intense band, whereas the CTAB method has generated the least intense band. Furthermore, the silica capture extraction method did not yield any RNA after extraction and electrophoresis. Consequently, it was concluded that, of these six methods, the lithium chloride technique and the Qiagen kit are the most appropriate for the extraction of viral RNA from sugar beet samples prior to RT-PCR for detecting BNYVV.

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Rhizomania is one of the most devastating diseases of sugar beet worldwide. The disease poses a serious threat to Moroccan production and it is capable of significantly decreasing quality and yield of sugar beet plantations. The long-term survival of its fungal vector (Polymyxa betae) in soil makes it a very difficult disease to manage. Therefore, this study investigated the potential of a non-pathogenic fungal Fusarium oxysporum strain Fo47 to control Polymyxa betae. This biocontrol agent was applied as soil treatment, seed treatment, or a combination of the both treatments. A bio-test was performed on treated soil. After four weeks of culture, the roots of sugar beet seedlings were retrieved and analyzed by the DAS-ELISA test. Results indicated that F. oxysporium Fo47 reduced the activity and survival of P. betae when compared to a reference biocontrol agent Trichoderma harzianum, which only revealed significant in reducing the viral load of Beet Necrotic Yellow Vein Virus (BNYVV) as seed treatment. The non-pathogenic Fusarium oxysporum Fo47 was more effective as soil treatment and allowed almost the same reduction of BNYVV virus concentration as T. harzianum 908. Therefore, our findings emphasizes that the performance of the biocontrol agent depends on the method of application.