| Dioscorea zingiberensis C. H. Wright is an endemic plant of China, and is alsoan important medicine material plant for steroid extracting for its high contents ofdiosgenin in its rhizome. But the germplasms have degenerated, lower content ofdiosgenin and lower production of rhizome by cultivation because of its confusionpropagation seedlings. We have no much knowledge about the genetic background.And there are any high quality breed at present. The resources investigation has beenmade firstly, then the Genetic diversity and Systematics by RAPD markers have beenstudied by author. A new germplasm "XHJ-401"(autotetraploid D. zingiberensis)with high content of diosgenin and high yield of rhizome has been created bychemical mutagen with itro culture; and the technique system of its mass clonalpropagation has also been established; its agronomic, biological and biochemicalcharacteristics have been studied; the triploid hybrid seeds from XHJ-401×AK havebeen obtained. The main results are as fellows:(1) An autotetraploid XHJ-401 (2n=4x=40) has been created through chemicalmutagen with itro culture from male of population TY. Its average output of rhizomeof the annual and biennial test-tube plantlets is at 7.87725×103 kg·hm-2 and8.70558×104 kg·hm-2 respectively, 141% and 373.11% higher than that of the biennialdiploid parents respectively; and its average diosgenin content is at 1.601% and 2.966% respectively; the latter is 255.21% and 81.30% higher than that of 2N and TYrespectively. It is higher or larger in photosynthesis rate, stomatic conductance,transpiration rate, content of chlorophyll a & b, Peroxidase activities, Catalaseactivities, size of stoma & guard cell, number & size of chloroplast in guard cell ofleaf than that in its 2n parents; both the adaptability in field and the growth conditionare better than that of the diploid. It lasts 306d～310d in period of growth anddevelopment, 37d～40d longer than that of the latter. Its inherited properties are stabile;and its high yield and stress resistance come from its special morphological andstructural organs, biological & biochemical characteristics. The chromosome numberof the hybrid from XHJ-401×AK is 2n=3x=30; and the pollen callus is n=1x=10.(2) The morphological diversity of D. zingiberensis has been studied. The naturalhexaploid and two tetraploids was found. The apomixes is possible in D. zingiberensis because the polyembryony has been found firstly. Beside the dioecious andmonoecious, the polygamomonoecious, polygamo-dioecious, hermaphrodite flowerwith sterility stamen, staminate flower and pistillate flower in the same inflorescencehad also been found. The sexual rate in nature is males: females: monoecious=55: 44:2. Tuberous rhizome, long clavate rhizome, heterophylly, vein depressed leaf was alsofound, The inflorescence of this species is catkin but spike. The organ morphologicdifferences changes in different populations, bodies, positions in plant, and habitats.(3) The male, female and monoecious plant of this species can be denaturalizedand changed each other; The denaturalization rate of XHJ-401, 2N & TY is 12.69%,10.83% & 10% respectively. The parthen carpy be approved, and the fruiting rate ofXHJ-401 (36.4%) is much more than that of AK (8.2%). It is a shade-enduring plant.The contents of diosgenln in rhizome is correlated with a few morphologic characters.We can use the color to estimate the diosgenin content only in the same germplasm.The width of guard cell can be used to judge the ploidy more credibly.(4) Comparative studies on the genetic diversity, population genetic structure ofD. zingiberensis have been made. It has been pointed that this species is a narrowspecies with higher genetic diversity, lower coefficient of gene differentiation (Gst)among populations, and higher estimate of gene flow (Nm). The main results are asfellows:①20 RAPD primers from 60 10-base arbitrary primers have been chosenfor their strong, reproducible amplification and distinct polymorphisms. 385 loci wereidentified with this oligonucleotide primers, out of which 220 loci were polymorphicand account for 57.14% of total genetic diversity at species level. The result showsthat the materials tested have a high level genetic diversity.②Analysis of geneticdiversity with POPGENE shows the genetic diversity of D. zingiberensis is higherthan that of other 5 species in the same genus; The Shannon's indices of diversity (I)and Nei's gene diversity (h) is 0.4737 & 0.6666 respectively. The genetic diversityamong species (h=0.4767, I=0.6697)=that within species (0.4737, 0.6666)=thatamong populations (0.4737, 0.6666)=that within populations=that amonggenerations (0.4500, 0.6414)=that of parents (AK: 0.4496, 0.6410)=that of F1(AKF1: 0.4409, 0.6308). The genetic diversity within populations is abundant; but it isobviously different in different populations. The genetic diversity of populations inthe south side of the Yangtsc Rive is larger than that in the north side of the river.③The Gst among species is 0.0709, larger than that among populations (0.0390) andthat among generations (0.0075). This means molecular variations exist mostly withinspecies but beteen species as for dioscorea; and mostly within populations but beteen populations as for D. zingeberensis.④The Nm among generations is 66.5163,larger than that among populations (12.3071), and much larger than that amongspecies (6.5516). The Nm of populations is large, but is different from population topopulation.⑤The analyses of Nei's genetic distance (D) between every every twospecies of Discorea showed that the value of D is D. gracillima(0.0289)＜D. Colletti(0.0612)＜D. nippanica subsp, rosthornii(0.0651)＜D. opposita (0.0733)＜D. bulbifera (0.0782); The D value of every two populations of D. zingiberensis is0.0067(AK-SM)～0.1575(TJ-SZH); Among 6 species: D=0.0289～0.1105, I(genetic identity)=0.9248～0.9715; D value of 3 species of Sect. Stenophora is theclosest, and Sect. Opsophyton (D. bulbifera) is the farthest. The D value betweenXHJ-401 and its parents (2N & TY) is 0.0350 & 0.0333 respectively; This means thatbig genetic variation has occurred between tetraplois XHJ-401 and its diploid parents.(5) UPGMA Clustering analysis to populations of D. zingiberensis shows thatthe taxa with same ploid has similar genetic distance; So, they can be grouped into asingle group early, this is called "population complex" (A new conception). The effectof ploid on genetic variation is much more larger than that of geographical obstructand spread distance; mountain' much more than fiver'. The differences of phenotypeand DNA can be caused by ploid doubled. So the biological effect of polyploid is notonly caused by accumulation effect of DNA, but also by other factors.(6) Molecular systematics system of taxa under species of D. zingiberensis hasbeen established. It shows that Sect. Stenophora is a natural taxon; and their evolutionsequence is from Section Stenophora to Enantiophyllum then to Opsophyton.(7) The geographical distribution map of D. zingiberensis has been ploted. Itshows the two main distribution area are not connected distinctly. So, the populationdiffusion is possibly along the lines of the Yangtse Rive and its branches from west toeast, and then branching to north and south respectively in the middle drainage area ofthe rive, and forming two subcentre, that is west Hunan and northwest Hubei. Thehigh mountains is the main obstruct factor for its population spread. D. zingiberensiscan distribute in three kinds of communities including forests, shrubs and tussock; andits natural distribution rate is at 50.2%, 34.6% and 15.2% respectively; and 48.4%,55.6%,45.2% respectively when the Canopy density is at 3～5.
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