Phenotypic and alpha-acid content diversity of wild hop populations in Croatia

An ecogeographical survey of wild hop populations was conducted in the northwest of Croatia in two consecutive years. A total of 121 plants was documented on eight locations. Along with the passport data, the data on three phenotypic traits (no. of leaflets, cone shape, aroma) were gathered during collection, while the content of a-acids in hop cones was determined by lead conductance. Shannonʹs information index was calculated for each phenotypic trait and was used as a measure of intra- and inter-population diversity. For all analyzed traits, most of the total phenotypic diversity was attributable to differences among plants within populations. The differences in proportions of individuals having a particular trait state between all pairs of populations in the case of leaflet number and cone shapes were non-significant. Four out of 28 pairwise comparisons for aroma were proven significant, indicating the existence of differences in proportions of individuals across populations recorded to have ʹtypical hoppy, ʹfine hopʹ or ʹroughʹ aroma. No significant differences were observed for a-acids content among populations. Plants exhibiting elongated cone shape had significantly higher a-acids content than those having oval or round cone shapes. Similarly, plants categorized as ʹroughʹ aroma hop cones had the highest content of a-acids compared with those categorized as ʹtypical hoppyʹ or ʹfine hop aromaʹ hop cones.