优良玉米杂交种的育成,要经过自交系的选育、杂交组合选配和鉴定、繁育推广等程序,一般需10年左右,时间较长。多年来,我们在南京地区采用就地一年种植两季的方法加速世代,大大缩短了育种年限,使一批优良杂交组合及时地在大面积生产上发挥了增产作用。高产、抗病、优质早熟单交种苏玉1号就是采用这种方法花了仅6年时间育成的。南京地区就地一年种植两季进行育种加代的主要技术措施: 一、春季利用弓膜或地膜覆盖播种利用弓膜和地膜覆盖播种,可使播期提前25～15天左右,同时薄膜的增温效应也加快了玉米前期的发育进程。据测定,至4月下旬,弓膜和地膜覆盖玉米的有效积温可比正 Good maize hybrid breeding, go through inbred lines breeding, hybrid combinations matching and identification, breeding and promotion procedures, generally takes about 10 years, a long time. Over the years, we have used the method of planting two seasons in one year in Nanjing to speed up the generations, greatly shorten the breeding years and make a batch of excellent hybrid combinations play an increasing role in large-scale production in a timely manner. High yield, disease resistance, high quality single cross Su Yu 1 is the use of this method took only 6 years bred. In Nanjing, planting two seasons a year in situ breeding and generation of the main technical measures: First, the use of bow or mulching spring sowing the use of arch film and mulching sowing, sowing date can be 25 to 15 days ahead of schedule, while the film by the increase Temperature effect also accelerated the development of early corn. It is determined that by the end of April, the effective accumulated temperature of bow and mulch maize is positive