选育玉米自交系所用的基础材料大致有三种:自由授粉群体(地方品种)、各种杂交种和改良群体。在五十年代到七十年代,我省玉米育种工作者都曾用地方品种大量分离过自交系,但育成的自交系不是配合力不高就是农艺性状欠佳,所以用于生产的不多。到八十年代,我省已普及玉米杂交种,地方品种在生产上已不多见。由于种植保存有一定难度,育种单位也不轻易地大规模使用。七十年代末期,我省一些单位着手群体改良工作,但因工作刚开始,改良群体尚需多轮的努力。所以,目前多数单位乐意用杂交种作为分离自交系的基础材料,即二环系选育,其 There are basically three basic materials used to breed maize inbred lines: free pollinators (native varieties), various hybrids, and improved populations. During the 1950s and 1970s, most of the maize breeding workers in our province used large numbers of landraces to separate inbred lines. However, the bred inbred lines did not have high combining ability or poor agronomic traits, so they were not used in production many. By the 1980s, corn hybrids were widely spread in our province, and local varieties were rare in production. Due to the difficulty of plant preservation, breeding units are not easily used on a large scale. In the late seventies, some units in our province started the work of group improvement. However, as the work started, the improvement of the group still required many rounds of efforts. Therefore, at present, most units are willing to use hybrids as the basic material for isolating inbred lines, namely,