Wheat viruses transmitted through the soil: how important for Italian durum wheat?

Durum wheat (Triticum turgidum L. subsp. durum (Desf.) Husn.) contributes 14% of total EU wheat production, and Italy represents the greatest European producer. This cereal can be affected by numerous pathogens, including various viruses that can significantly compromise productivity. In particular, a number of soil-borne wheat viruses have been reported throughout the world. Two soil-borne viruses have been reported in Italy on wheat: soil-borne cereal mosaic virus (SBCMV) and wheat spindle streak mosaic virus (WSSMV). Both viruses have a ssRNA genome and are transmitted by Polymyxa graminis Led., a plasmodiophorid that can persist in soil for up to 20 years. Although these two viruses have been described more than twenty years ago, their real prevalence in the Italian wheat-producing areas remains unknown. This lack of knowledge is caused mainly by two factors. First, the difficulty in distinguishing symptoms caused by these viruses from plant nutritional imbalances or physiological stress. Second, lack of fast, sensitive and cost-effective detection tools. Actually, the detection assays currently available are costly and time-consuming (RT-PCR) or have limited sensitivity (ELISA). Since the prevalence and severity of these viruses are expected to increase due to climate change, there is a need for new detection tools, with improved performance: no extraction steps, very fast results (minutes), and a sensitivity that allows the pooling of a large number of samples. We have developed two protocols for the rapid, easy and highly sensitive detection of SBCMV and WSSMV that can be used in the field to simplify the surveillance of these viruses. The protocols are based on a reverse transcription loop-mediated isothermal amplification (RT-LAMP) and can be performed on plant crude extracts, without the need for RNA extraction. The sensitivity of RT-LAMP compares well with RT-qPCR, with the obvious advantage that it produces results in minutes rather than hours.