Visacane, an innovative quarantine tool for the exchange of pest and disease-free sugarcane germplasm

Sugarcane varietal improvement can not exclusively rely upon exchange and introduction of genetic resources via true seeds (fuzz). It also requires the introduction of vegetative propagation material (cuttings, tissue-cultured plantlets). The continued increase in international and intercontinental trade in plants has led to the enforcement of quarantine measures before introduction into a country because many plant pathogens can be carried and transmitted by vegetatively propagated material. Visacane is the new name of Cirad's sugarcane quarantine (http://visacane.cirad.fr/en/). It covers three main quarantine procedures: detection of pests and pathogens, elimination of pests and pathogens, and transfer of plant material free of pests and pathogens. It has been devoted to sugarcane quarantining for several decades. Besides phytosanitary constraints, Visacane takes also into account legal constraints and ensures, through appropriate contracts, that plant breeders' intellectual property rights over the transferred material are respected. Unlike most sugarcane quarantines that are essentially used to import sugarcane germplasm into a country, Visacane can import and export varieties from and to most sugarcane growing countries in the world, ensuring that the material is free from any important pest and disease causing pathogen. Until recently, the sugarcane quarantine process was aimed at detecting known pathogens harbored by the plant material and eliminating these pathogens whenever possible. It is an a priori process, because it only takes into account the pathogens that have been previously described and for which efficient detection tools exist. During the last three decades, several new viruses infecting sugarcane have been discovered, including Sugarcane bacilliform virus, Sugarcane yellow leaf virus, Sugarcane streak mosaic virus and the virus associated with Ramu stunt. In addition, the etiology of chlorotic streak, a disease known since 1929, has not been elucidated so far, although there is evidence for its infectious nature. Therefore, it can be assumed that unknown pathogens are still to be discovered in sugarcane, especially if these pathogens do not cause symptoms that can be easily observed. For these reasons, the research team associated with Visacane is setting up a new strategy of diagnostics, the so-called sequence-independent approach which aims at deciphering the virome (= the genomes of all the viruses that inhabit a particular organism). We believe that our forthcoming combined process, that will include our traditional approaches in addition to the metagenomics approach, will drastically improve our routine quarantine diagnostics. (Texte intégral