Study On Genetic Diversity Of Zoysia Willd. Germplasm Resource

Zoysia grasses (Zoysia spp.) are widely used as warm season turf grass indigenous to the countries of the western Pacific Rim. They possess excellent wear tolerance, drought tolerance, disease resistance, salinity tolerance, low fertility tolerance and low maintenance requirements.Forteen morphological characteristics, phonological phase, seed yield and its component, stolon growth rate of representative accessions of5species and1variety of Zoysia Willd. were observed in this report. The leaf low temperature of97accessions of5species and variety of Zoysia Willd. was evaluated using modified electrolyte leakage method, and15representative accessions were selected based on leaf low temperature result to evaluate the low-temperature tolerance of stolons and rhizomes using survival rate, and then soluble protein of three organs of two extreme low temperature tolerant representative accessions were studied using SDS-PAGE electrophoresis. Morphology, isozyme and SSR genetic markers at three different levels were studied combining with the geographical distribution to study the genetic variation and interspecific relationship of59accessions of Zoysia Willd. belonging to9species and1variety. The study will provide an important scientific basis for the development and untilization of zoysiagrass germplasm resource in China.The main results were stated as followings:1. Variation analysis on morphological characteristic of Zoysia Willd. in ChinaThe variations and tendencies of14morphological and their correlationship of124accessions of Zoysia Willd. were studied in the paper. The results showed that the great variation of morphological characteristics were existed among the accessions of Zoysia Willd.with the coefficient of variation (CV) at exceed10%. Correlation analysis indicated obvious correlation were existed among some of14morphological characteristics at significant levels. Some morphological characteristics was correlated siginificantly with latitude or longitude. Four groups were divided based on14morphological characteristics: fine zoysiagrass, inflorescenced coarse zoysiagrass, less-inflorescenece coarse zoysiagrass and Z099.2. Study on the variation of phenological phase of Zoysia Willd.The phenological phases of109accessions of Zoysia Willd. including5species and1variety were observed. The results showed that there is difference in the date of phonological phases among different accessions in Nanjing. Variation scopes of blooming stage and wilting stage was biggest, and that of green period was215-277d. The date of initial booting stage has a significantly positive correlation with the date of initial blooming stage, blooming stage, maturation stage and wilting stage and length of green period. The date of wilting stage has a positive correlation with the length of green period, and that of turning-green stage has a highly significant negative correlaion with the length of green period. Regression analysis indicated that turing green, initial booting, initial blooming, blooming and wilting stages of Zoysia Willd. became obviously earlier with latitude increasing. The phonological phase of coarse texture accessions was earier than fine texture accessions relatively.3. Study on propagation properties of Zoysia Willd. in ChinaThe stolon growth rate, the seed yield and its component of Z. japonica and Z. sinica in China were measured and analyzed. The results showed that in Nanjing:(1) abundant variation was existed in the total stolon length and aboveground biomass of different accessions of zoysiagrass;(2) the total stolon length was positive corrected with the aboveground biomass with correlation coefficient as0.676;(3) abundant variation was existed in the seed yield and its component, in which seed yield had the highest variation with the coefficient vatiation (CV) as102.51%;(4) seed number per spike and the weight per100seeds were positive corrected with seed yield, inflorescence density was not corrected with seed yield directly, but seed yield was correlated with inflorescence density, seed number per spike and the weight per100seeds after they interacted;(5) path analysis showed that seed number per spike and the weight per100seeds contributed the most to the seed yield, inflorescence density contributed few;(6) above ground biomass was negatively correlated siginificantly with inflorescence density;(7) the multiple comparisons analysis of the total stolon length and seed yield revealed the vegetative growth rate of six accession such as Z015,Z013, Z056et al was high, nine accessions such as Z016, Z052and Z061et al have high seed yield, six accessions such as Z012, Z063et al have high seed yield and vegetative growth rate, and the vegetative growth and seed yield of five accessions such Z111, Z018et al was both low.4. Study on Low Temperature Tolerance of Zoysia Willd.4.1The assessment of the Low Temperature Tolerance of Zoysia Willd.The leaf LT50of97accessions of5species and1variety of Zoysia Willd. were evaluated by electrolyte leakage, then stolon and rhizome low temperature of15representative accession were evaluated by survival rate. The leaf LT50of Zoysia Willd was from-1.9℃to-10.4℃with coefficient of variation (CV) of27.79%, and the LT50of different species of Zoysia Willd were ranked as follows:Z.japonica.<Z. sinica.<Z. matrella.<Z. tenuifolia.<Z. sinica var. longiflora.<Z. macrostachya. The LT50variations of Z. japonica, Z. sinica and Z. matrella were big with CV at exceed20%. The R value among the LT50of different organs were significant at5%probability level.4.2Soluble proteins variation in zoysiagrass after cold-acclimationSoluble proteins in leaves, stolon and rhizome of Z125(poor cold tolerance) and Z141(strong cold tolerance) in non-acclimation (28℃/22℃, day/night,8h light) and simulated low temperature acclimation(8℃/2℃, day/night,8h light) were studied. SDS-PAGE electrophoresis revealed that after two weeks of cold acclimation, the soluble protein synthesis in Z125had a major change, a new40KD protein components in rhizome and a66KD in leaves in cold-acclimation comparing to the non-acclimation; a more50KD and less40KD protein components changed in rhizome in cold-acclimation Z141comparing to non-acclimation Z141.After4weeks of cold-acclimation, two new protein compositions, about60KD, appeared in cold-acclimated Z141both stolon and rhizome, about60KD and20KD soluble protein compositions were disappeared in cold-acclimated Z141leaf. And only2new soluble protein compositions,about50KD, appeared in cold-acclimated Z125rhizome.5. Study on Genetic Variation and Interspecific Genetic Relationship of Zoysia Willd.5.1The morphological markersWith observing and measuring23morphological characteristics on59accessions of Zoysia Willd., the results showed as:The accessions of Z.matrella had greatest variation on most characters, Z.japonica and Z.sinica had great intraspecies differentiation but smaller than Z.matrella, and the degree of genetic diversity within species of these two were very close. The accessions of Z.koreana Mez. had little differentiation on many characters respectively, and the genetic diversity of Z.koreana were smaller;②The cluster analyzing results show:All these species can be classified by genetic distance to be3classes:the first class included of Z. japonica and Z sinica, Z. koreana and Z. macrostachy., the second class included Z. tenuifolia, Z. matrella, Z. minima Zotov. and Z.sinica var. longiflora, Z. macrantha was clustered to be a group itself;③The principal components analyzing results showed that the width of blades, the length and diameter of stolons, the spikelets number of one spike, the length of spikelets and the pedicels, the height of procreant culms, the ligule colour, whether ligule with hairs or not, these features are important in researching of the genetic relationship of species.5.2Isozyme studyThree isozyme systems (MDH、EST、POD) were conducted on59accessions of Zoysia Willd. to study the genetic relationship of species. The results show as follows:①the genetic diversity was ranked as:Z.matrella> Z. japonica> Z.sinica> Z.koreana.;②the clustering analysis results show:Z. japonica and Z. sinica> Z. sinica var. longiflora and Z.macrostachya were clustered together; Z.matrella、Z. tenuifolia were clustered to be a group, then Z.minima、Z. pacifica、Z. macrantha were also clustered to this group; Z.koreana was clustered to be a group by itself.5.3SSR analysisSSR markers were used to study the genetic relationship of accessions of Zoysia Willd..①The genetic diversity within species ranked as:Z.japonica, Z. sinica> Z. koreana> Z. matrella;②Z.japonica was clustered together with Z. sinica, Z. macros tachya and Z koreana; Z. matrella was clustered together with Z. tenuifolia and Z. minima; Z. macrantha and Z.sinica var. longiflora was a group by itself respectively.6. The evaluation of turf value of Zoysia Willd. germplasm in ChinaThe turf value of74accession of Zoysia Willd.in China were evaluated based on leaf color, density, leaf width, uniformity, green period, low temperature tolerance and rust resistance index. The result showed that ten accessions including Z014、Z075、Z008、Z142、 Z042、Z005、Z044、Z101、Z053and Z050were dark-green, dense, long green-period and common low temperanture tolerance, and the turf quality of these accessions were very high. Ten accessions including Z118、Z081、Z010、Z115、Z104、and Z103et al were yellow-green, short green-period and low tolerancc to low temperature and rust, the turf quality of these ten accessions was very low. The the turf value of other54accessions were intermediated due to two or three poor index.