Fast and sensitive detection of soil-borne cereal mosaic virus in leaf crude extract

Soil-borne viruses of cereals have been reported in several countries, however the damage they cause is difficult to evaluate, likely due to a lack of fast and cost-effective detection tools. In Europe two soil-borne viruses are known to infect wheat, the best known being soil-borne cereal mosaic virus (SBCMV). SBCMV is a furovirus with rigid rod-shaped particles containing a ssRNA genome, and is transmitted by Polymyxa graminis Led., a plasmodiophorid that can persist in soil for up to 20 years. SBCMV was reported on common (Triticum aestivum L.) and durum [Triticum turgidum L. subsp. durum (Desf.) Husn.] wheat, as well as on the less cultivated rye and triticale. Information about actual spread of this virus is still limited. Detection protocols currently available are costly and time-consuming (RT-PCR) or have limited sensitivity (ELISA). Above that, the presence of SBCMV is often mistaken for physiological or nutritional problems. To overcome obstacles that so far prevented to know the real diffusion of SBCMV, we have developed a new procedure that requires no extraction steps, is very fast (minutes), and has a sensitivity that allows pooling of a large number of samples. An added value is the possibility to perform the tests at the point of care (POC). The protocol, based on reverse transcription loop-mediated isothermal amplification (RT-LAMP), was first optimized on leaf crude extracts from laboratory-grown wheat plants, and then validated on field samples using a portable device. We envisage that it will ease future extensive field surveys.