Varieties producing green fruit, less strongly-flavoured and sweeter than typical blackcurrants, are cultivated in Finland, where they are called "greencurrants" ("viherherukka"). In Poland, the Research Institute of Horticulture has done work on improving the blackcurrant with regard to disease and pest resistance, fruit quality, adaptations to local conditions and mechanical harvesting. Researchers have crossed various varieties and introduced inter-specific genetic material from the gooseberry ("Ribes grossularia"), the red currant ("Ribes rubrum") and the flowering currant ("Ribes sanguineum"). The resulting offspring were further back-crossed to "R. nigrum". Cultivars produced include 'Tisel' and 'Tiben' in 2000 and 'Ores', 'Ruben' and 'Tines' in 2005. Further cultivars 'Polares' and 'Tihope' are being tested. Since 1991, New Zealand has become an important centre for research and development, as its temperate climate is particularly suitable for cultivation of the crop. Breeding programmes are concentrating on yield, large fruit size, consistency of cropping and upright habit.