BREEDING FOR EARLY MATURITY AND HEAT-TOLERANT SPRING BREAD WHEAT

The Republic of Uzbekistan annually cultivates autumn cereals on 1,200,000 hectares of irrigated area, yielding an average of 55 quintals per hectare. In the southern regions of the republic, in Surkhandarya and Kashkadarya regions, heat and drought conditions of cereal crops during the ripening period have a significant impact on the yield of autumn cereals. Also in the republic of Karakalpakstan and in Horazm region as a consequence of very cold and dry winter, and dropping of air temperature up to -30 degrees bring about perishing 50-60% of autumn cereal crops. Taking into account this, creating early spring wheat varieties in increasing soil temperature, finding initial sources and carrying out scientific researches on them are considered to be an important task. Taking into consideration of problems given above, the researches were fulfilled on spring bread wheat by grain and leguminous crops research institute in the conditions of Karshi district of Kashkadarya region and Chimbay district of the republic of Karakalpakstan. In the conditions of Kashkadarya region delaying in sowing spring wheat varieties causes a contraction of period between varieties before germination, and in the condition of the republic of Karakalpakstan this indicator was observed to continue according to the biology of the varieties. In the condition of Karshi district sharp increasing air temperature in late spring months and decreasing relative air humidity declines germination period, and in the condition of Chimboy district not to decrease relative air humidity affects germination period of plants according to the biology of the variety. As well as, among studied varieties hot tolerance Kr-SpR2014-3, KrJ-SpR2014, Kr-SpR2014-6, Kr-Sp/2010/59, Janub gavhari, Kr-SpR2014-13, Kr-SpR2014-19, Kr-SpR2014-20, Kr-SpR2014-21 and Kr-SpR2014-22 varieties were chosen in order to use in next stages of the selection.