Study On Genetic Diversity Of Dioscorea Esculenta Germplasms

Dioscorea esculenta (lour) brukill, a liana species of Dioscoreaceae, its underground tuber has high medicinal and nutritional value. In this study, morphological markers and molecular markers methods were applied to detect the genetic diversity and phylogenetic analysis relationship of 129 germplasms. The results could provide scientific basis for making right protection strategy, fostering new cultivars and regulating of high quality, high-yield cultivation. The main results are as follows:1. The phenotypic data was obtained by filed investigation records of the agronomic characters.129 accessions was clustered by SAS software, most of the accessions were clustered as a large group, which have similar characters of low yield per plant and middle leaf (30.0-50.9cm2).12 accessions were clustered as a group, which have similar characters of moderate yield per plant and relatively smaller leaf(<30.0 cm2). No.22 and No.104 were clustered as a group, which have similar characters of low yield per plant, short tubers, and relatively smaller leaf(<30.0 cm2). No.51 was clustered alone, which has characters of high yield per plant and large leaf(>50.9 cm2). No.76 was clustered as a group, which has characters of high yield per plant and relatively smaller leaf(<30.0 cm2).2. A total of 10 RAPD primers were selected from 200 primers, and 66 amplified sites were detected, of which 58 (87.9%) were polymorphic. UPGMA clustering results demonstrated that genetic similarity coefficient of 129 materials was ranged from 0.436 to 0.929, with the average of 0.674.Mostly materials were clustered into the same group which shown the less genetic differences among the materials; No.121 and No.122 material were clustered into a single group, No.95 material was clustered into the other group by itself,These accessions were obviously different from the other ones, a comparatively higher genetic diversity were represented.3. A total of 10 ISSR primers were employed on 129 individuals of D. esculenta from 200 primers, and 93 amplified polymorphic sites were detected, of which 89 (96.8%) were polymorphic loci. UPGMA clustering results demonstrated that genetic similarity coefficient of 129 materials is ranged from 0.484 to 0.892, with the average of 0.687. It show that mostly materials were clustered into the group which have less genetic differences among the materials; No.68 and No.95 materials were clustered into two group separatly, both of them were obviously different from the others, which have comparatively higher genetic differences.4. Comparison of the data obtained by RAPD and ISSR analysis on the 129 accessions showed that both of them could be clearly distinct from each other. All of the accessions were clustered into 3 groups with GS=0.625, most of them were clustered together except No.95 that clustered alone. No.121 and No.122 were cluster into another sigle group with GS=0.64 by both of the methods. No.68 was clustered alone by ISSR analysis but which was clustered into other group by RAPD analysis, these differences may be due to different specific fragments that were amplified by these two methods. The results above showed the similar cluster results and genetic diversity of these two methods with high correlation.5. The genetic diversity of 129 D. esculenta accessions was compared by morphological and molecular markers. No.117 and No.119 were cluster together with the characters of small leaf area and low yield per plant by morphological markers. Meanwhile, the least genetic distence was found between No.117 and No.119 by RAPD(0.07) and ISSR(0.11) which showed the correlation of these two kind of markers. But there are differences between them, such as No.51 was clustered alone by morphological marker, but was clustered with other accessions by molecular markers. There are advantages and disadvantages of morphological and molecular markers, the combination of these two kind of markers could reveal the genetic diversity more better.6. All the results above showed the rich genetic diversity among these 129 D. esculenta accessions. Most of accessions were clustered together by moleculer markers with characters of low yield per plant, poor quality, less genetic difference. But there are some accessions with similar morphological characters shown larger genetic differences, such No.65 and No.95, which are the good canditate for D. esculenta breeding. The decreasing of the yield and quality of D. esculenta was result from the defect of high quality cultivars and proper planting techniques, which may further influence its larger area plantation. It is suggestion that tissue culture of high quality and yield D. esculenta should be involved and D. esculenta germplasm should be collected preserved and estimated in order to utilize it more scientifically and properly.