Production of Virus-free Vitis Vinifera ‘koshu’ Plantlets From Shoot Tips or Axillary Buds 

Abstract Objective: Vitis vinifera ‘Koshu’ is the most important grape cultivar for producing white wine in Japan. Most Koshu vines are heavily infected with viruses of multiple types, such as grapevine leafroll-associated viruses, which severely interfere with normal development and physiology such as photosynthesis of grapes. The meristem culture method has been the most commonly and successfully employed to eliminate viruses from grapevines. Koshu is, however, known for its difficulty of regenerating plantlets from meristems. Results: We have established a robust method of regenerating plantlets with high frequency from shoot apical meristem tissues of ‘Koshu’ grapevines. The key points of this method are the use of (1) no or low concentrations of 6-benzyl-aminopurine (BAP) (0.22 µM) for shoot regeneration, and (2) a synthetic auxin, such as 10-5 M 4-chloroindole-3-acetic acid (4-Cl-IAA), for rooting. This method should be very useful and important for producing ‘Koshu’ virus-free vines.