农作物品种是在一定的生态条件下,经过长期的自然选择和人工定向培育的结果。任何一个品种总有一定的适应范围,不存在适应一切地区、一切年份的“万能”良种,因此,这就有一个品种选择的过程。品种的选择过程包括两个方面:一是品种的更新,即对每年使用经受了各种自然条件的考验,表现出高产、稳产、质佳、 Crop varieties are the result of long-term natural selection and artificial cultivation under certain ecological conditions. There is always a certain range of adaptability for any species, and there is no “universal” variety adapted to all regions and all the years. Therefore, there is a process of variety selection. Variety selection process includes two aspects: First, the variety of updates, that is, the use of each year to withstand the test of a variety of natural conditions, showing high yield, stable yield, good quality,