| The genetic diversity of Agropyron was assessed from three degree: morphology, cytology, and RAPD markers. Analysis was performed within and between populations and species. The following materials were used in this experiment: 27 populations involving 3 species of Agropyron collected from Xinjiang in 1998, 21 populations involving 2 species of Agropyron collected from Inner Mongolia in 1999, 12 populations involving 4 species and 1 subspecies of Agropyron collected from the other areas of China, and 7 populations involving involving 2 species of Agropyron introduced from other countries. The major results are as follows:1.The genetic diversity was analyzed in morphology and cytology in the populations collected from Xinjiang and Inner Mongolia. A. cristatum was the most common species in both areas. A total of 3 species were found in Xinjiang and showed three ploidy levels: diploid, tetraploid, and hexaploid. The hexaploid collection was found in China for the first time. Only two species were collected in Inner Mongolia. These Agropyron occurred at two ploidy levels: diploid and tetraploid.2.Analysis was performed within and between populations, species by R.APD markers. The 100 random decamer primers were emploied in amplication reactions. Among them, 20 primers were informative and yielded some scortable bands. The level of polymorphism varied between different taxonomic units depending on the primers emploied. The Jaccard similarity coefficients of different taxonomic were calculated and the results were used to produce a cluster diagram using the unweighted pair-group methed (UPGMA).3.In order to optimize sampling strategies, 30 plants of one population from Xinjiang analysed by RAPD markers. 30 plant fell into 12 groups. If a new population formed by the 12 plants from each group, this new population could make up 80% genetic diversity of the 30 plants.This result suggested that no less then 12 plants be collected in a collection site.4.The genetic diversity within population was analysed on 10 plants of one3population by RAPD markers. The result revealed that the genetic diversity withinpopulation was high and correlated with its allogarnous reproductive system.5. The genetic diversity of inter-popuIation was asseesed on l0 ntulpopulations. The result revealed that the genetic diversity of inter-population wascorrelated with the geograPhical origin of the collections, and the germplasm of A.crdrium in China had much more genetic diversity comPared with othersoriginated from other countries.6. The relationships between 5 species were investigated using two populationsof each specie. A total of l0 populations of 5 species fell into 5 groups, and tWopopulations of each specie were clusted into one grouP except one specie, A.desertOrum. For the tWo populations of A. desertOrum, one population was clustedinto one grouP with tWo populations of A. michnoi, and the other was separate.This result revealed that these tWo species might closely be relatCd in genetics.However, it was also thought that the result was affected greatly by geograPhicalorigin of the collections.7. The relationships of A. desertOrum ssp. pilOsiusculum with A. cristatum (2X,4X), A. mongOlicum, and A. desertorum were also analysed. The result revealedthat the A. dertOrum ssP. piIosiusculum and A. mongOlicum were most related. msresult showed that it should be discussed newly tha the A. desertOrum ssp.pilOsiusculum was treated as a subsPecies of A. desertOrum in the Flora of China...
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