Influence of Apple Mosaic Virus on the Growth, Yield, and Qualities of Saaz Hop

Abstract

The aim of this study is to elucidate the influence of apple mosaic virus (ApMV) infection on Saaz hop in the Saaz region of Czech Republic. The comparison between virus free and ApMV infection for the growth, yield and qualoties of Saaz hop was studied in one test garden in detail over two consecutive years (2010 and 2011). ApMV weakened vegetative growth and decreased hop cone yield. ApMV infection resulted in a decrease in the production of humulone (alpha acid) and essential oil. The composition of terpene compounds, which contribute to the hoppy aroma of beer, were also affected. ApMV-infected hop cones had lower ratio of mono-terpenes, and higher ratio of sesqui-terpenes than those derived from uninfected plants. Beer brewed using ApMV-infected hops had a diminished fruity aroma compared to beer brewed using uninfected hops. From these results, protecting hop plants from ApMV infection is important for maintaining both quantity and quality of hop. In some commercial gardens, it was confirmed that hop plants have been maintained virus-free for over 20 years. This fact suggests that good field practices can protect hop plants from virus infections.