FPS has used microshoot tip tissue culture therapy to eliminate viruses from grape cultivars for more than 20 years. The process is successful in eliminating viruses in over 85% of the selections. FPS has processed thousands of grape selections of over 750 cultivars. Many of these selections were processed even when the original plant material tested negative for viruses to meet the rigorous standard that FPS set for grapevine foundation material, referred to as Protocol 2010. Protocol 2010 standards require that vines must be generated using microshoot tip culture and be tested for an extensive list of pathogens. Vines meeting Protocol 2010 standards are planted in a foundation vineyard at Russell Ranch on the UC Davis campus. Since new pathogens may be identified at any time, microshoot tip culture may be considered a preventive measure to limit the presence of viruses and other pathogens in foundation stock.
Microshoot tip tissue culture is the regeneration a single plant from a single, minuscule (approximately 0.4–0.5 mm in size) explant including the meristem and one to three pairs of leaf primordia. Excision requires skill, patience, and lots of practice. This video describes the steps before and after excision and shows a meristem tip being excised under a microscope. The whole process from excision in tissue culture to harvest of dormant cuttings can take anywhere from 5 to 10 years. FPS is working on ways to shorten this time using HTS testing to release it under a provisional status.
