ABSTRACT
<p><b>OBJECTIVE</b>To study difference among populations which belong to Astragalus membranaceus and A. membranaceus var. mongholicus on morphology, habit, characteristics of physiology and resistance to powdery mildew, and classify them in order to provide theoretical basis for breeding and improving varieties.</p><p><b>METHOD</b>Morphology, habits, isozyme and soluble protein electrophoretograms were compared among the populations. They were categorized by cluster analysis based on those electrophoretograms. Different ability of resistance to powdery mildew was also studied through comparing disease indices among six populations.</p><p><b>RESULT</b>The results showed A. membranaceus var. mongholicus was distinctly different from A. membranaceus. There was a special type in colonies of A. membranaceus, which showed hairy upper epidermis of leaflets and later florescence.</p><p><b>CONCLUSION</b>Astragalus for medicine could be categorized in three types A. membranaceus var. mongholicus, A. membranaceus early florescence type and A. membranaceus late florescence type. Among them A. membranaceus var. mongholicus is most resistant to powdery mildew, while A. membranaceus is easily infected, and the early florescence type is even more easily infected.</p>