Uzbekistan has grown cotton for over 200 years, developing strains adapted to the regional conditions. However, changes in growing conditions over the past few years have demanded new strains. Three institutes are responsible for breeding superior varieties of cotton. The Ministry of Agriculture tests and certifies candidate varieties prior to commercialization. Although some problems exist, the variety approval process generally performs well. The most important change in growing conditions has been an increase in soil salinity because of massive diversion of water for irrigation from the Aral Sea. Drainage of this sea, which has lost 75 percent of its volume in about 30 years, has also drastically affected weather patterns. Wilt is another problem causing significant loss in yield.