THE EVALUATION OF THE VIRUS-FREE HOP QUALITY AFTER 5 YEARS GROWING INTHE CZECH-REPUBLIC

Virus-free hops are grown at considerable area at the present time (19 96). It represents 13% of total hop gardens area (including new planti ngs from the year 1996). Virus-free hops still hold (i.e. five years a fter first planting in the year 1991) considerable quality and quantit y advantages comparing with traditional hops. They contain substantial ly more hop resins, the content of alpha bitter acids is higher by nea rly 100% in dependence on the year of harvest. Content of beta bitter acids changes slightly and does not exceed 10 to 15% as a rule. The an alyses of hop oils confirm presence of farnesene as the most important marker of the Saaz semi-early red-bine hops in hop oils. Virus-free h ops give ki her yield. The difference, comparing to traditional hops, is the most significant in the first crop. After achievement of full e ffectiveness virus-free hops give higher yield by 20 to 25%. No reinfe ction by ApMV has not been detected yet.