Abstract: The anti-oxidant enzymes including SOD, POD and CAT and MDA, which is one of the oxidant products, and IAA and ABA, which were relative to earliness but not to decrepitation of the short-season upland cotton (SSC), were studied. The changes and hereditary characters of these biochemical substances at different development stages in different types of short-season upland cottons were studied. CAT activity and ABA content in SSC had significant maternal effect. The activity of SOD, the contents of soluble proteins, IAA and MDA showed significant dominant effect. The activity of POD and the contents of ABA showed significant additive effect. Based on the changes and genetic development, the biochemical assistant breeding technology was established and the relative selective standards, i.e. the selective range, activity of enzymes and time, were determined. Zhongmiansuo 20, 24, 27, 36 and so on were successfully bred by using the biochemical assistant breeding technology.

Key words: Short-season upland cotton, Earliness but not decrepitude, Biochemical substance, Assistant breeding