To Study the Heat Resistance Features of Bread Wheat Varieties and Species for the Southern Regions of the Republic of Uzbekistan

Wheat (Triticum aestivum L.) is considered one of the world's most important cereal crops. Every year 704 million tons of grain is produced worldwide. Bread wheat croplands cover 17% of the total crop area. In recent years, sudden changes in air temperatures have a negative impact on the morphological, physiological, biochemical and molecular properties of wheat and grain yield. Therefore, it is important to create high-yielding and resistant varieties of bread wheat to abiotic factors and to develop its primary source in the condition of different regions. In the result of this study, the influence of high temperature which varied from 30°С and above continuously during spiking and maturation period of grain, especially in the period of grain filling, on grain quality and productivity has been studied thoroughly for southern parts of Uzbekistan. Mostly, winter bread wheat varieties are grown in these southern regions. The optimal sowing time in autumn season is the second decade of October. In order to determine the heat resistance of the winter wheat varieties that are mostly grown in the Republic and selected in the result of breeding, the experiments and observations were carried out on optimal and late sowing periods. The optimal planting time was found to be appropriate on the 15th of October and for late sowing the 15th of November. At the same time, late sown varieties and samples are divided into resistant and non-resistant groups due to the delay in the maturation period and greater exposure to heat. At the study, temperatures during the growth period were calculated and daily temperatures during the grain filling period were determined too, and the influence of air temperature on growth phases, height of plant (cm), spike length (cm), number of spikelets in a spike (pieces), grain weight in a spike(g), weight of 1000 grains (g), grain nature (g/l), protein amount (%), gluten amount (%), its changes and the results in optimal and late periods were studied by comparing them.