Limited occurrence of Tristeza in Yuzu and possible Tristeza-free cultivation in northernmost commercial Yuzu-producing areas of Japan

Abstract

Citrus tristeza virus (CTV) commonly infects Yuzu (Citrus junos) in most parts of the citrus-growing areas in Japan. This study examined the occurrence of CTV in the northernmost commercial citrus- producing areas of Japan. Colonies of the brown citrus aphid (Toxoptera citricidus) were detected within the areas investigated. However, 23 of the 41 trees that were examined by RT-PCR and both or either subject to stem-pitting observation and immunostrip testing were free of CTV. Several CTV- free trees were apparently more than 60 years old. A field trial revealed that all eight uninoculated seedlings tested negative for CTV at 52 months after transplanting. These results suggest that CTV- free Yuzu production is possible in the Rikuzen-Takata and Ofunato areas of Japan.