Germplasm Exploration,Utilization And Molecular Genetic Diversity Research Of Ixeris Polycephala

Ixeris polycephala is an excellent grass-fodder and high-quality annual Asteraceae forage, which is important grass species for grassland animal husbandry development in China. Up till now, the number of self-breeding Ixeris polycephala varieties are comparatively less, besides introduced varieties become confused in market management, so it would be particularly important to breed new varieties, besides obvious differences in agronomic traits and genetic level among varieties are fundamental basis for identification, market application and directional breeding of Ixeris polycephala. This assay using the Ixeris polycephala germplasm as material, investigated phenotypic variation rules through quantity characters of Ixeris polycephala, analyzed production differences of Ixeris polycephala varieties (lines), along with SRAP molecular marker utilization to analyze genetic diversity of Ixeris polycephala. Additionally, constructed the Ixeris polycephala varieties (lines) DNA fingerprint based on EST-SSR and SRAP marker. The key results were as follows:1. Phenotypic variation analysis of Ixeris polycephalaThrough 11 phenotypic character among 30 Ixeris polycephala materials for investigating phenotypic variation character in different types, in order to provide the basic reference for breeding and improvement of Ixeris polycephala. There were wide range of variation within phenotypic character of Ixeris polycephala, the third reproductive branch had the most significant variance coefficient of 38.04%, followed by reproductive height and flower number, while leaf length had the least variance coefficient of 11.87%, wild type reached highest variation extent as 46.37%. There was significant correlation among these phenotypic characters. The wider and longer leaf of Ixeris polycephala were tall plants with strong stem, longer inflorescence, more reproductive branches.The cluster analysis showed that the materials could be divided into four groups with similar phenotypes which the first and second group belonged to narrow leaved creeping type, third group belonged to mid-wide leaved erect type, and forth group belonged to wide leaved erect type. Principal component analysis showed the fore three principal components accumulated at 71.904%, and indicated that the differences among Ixeris polycephala materials derived from plant height, stem diameter, the size of leaves and flower number. Thus, leaf number, third reproductive branch number, floret number of Ixeris polycephala had ample genetic variation, could provide important basic reference for phenotypic identification.2. Analysis productive performance of 15 annual Ixeris polycephala varieties(lines)By way of field trails, studied on the agronomic traits of 15 Ixeris polycephala varieties(lines) in Ya'an, southwest of Sichuan Province. The results showed that the new lines growth period of Chuanxuan No.1 and L5-4 were longer than Longmu (P<0.01). During two years from 2013 to 2014, the yields of new lines Chuanxuan No.1 were the highest, especially had advantage of yields at second defoliation and regeneration. Comparing with Longmu, the average hay yields of the new lines Chuanxuan No.1 reached at 5585 kg/hm2,increased 64.75%(P<0.01). In the aspect of stem-leaf ratio, the highest leaf-content was the new lines L5-4,second on the ranking was new lines Chuanxuan No.1, the stem-leaf ratio were 0.52 and 0.55 respectively. In terms of nutrients, the new lines Chuanxuan No.1 had abundant minerals and high nutritional value, the crude protein achieved 26.12%, and crude fiber achieved 12.11%. Thus, the new lines Chuanxuan No.1 and L5-4 with high yields and rich leaves were suitable for planting promotion in southwest of Sichuan province.3. Analysis genetic diversity of Ixeris polycephla revealed by SRAP markersResearch the genetic relationship and diversity of 30 Ixeris polycephala based on Sequence-related amplified polymorphism,32 SRAP primers were screened according to high polymorphism and clear bands from 209 SRAP primers. The 32 SRAP primer pairs amplified a total of 430 bands including 381 polymorphic bands among 30 Ixeris polycephala varieties (lines), and the ratio of polymorphism was as high as 88.86%.The average genetic similarity coefficient of cultivated new lines was 0.837, and the varieties genetic similarity coefficient was 0.805. As known by the POPGENE software results, the Nei's gene diversity (H) values ranged from 0.1283 to 0.2603,and the Shannon's information index values (I) ranged from 0.1898 to 0.3943,the polymorphic bands and Nei's gene diversity (H) values and Shannon's information index values (I) of the clutivated new lines were slightly higher than Ixeris polycephala varieties, indicated there was certain similarity between cultivated new lines and varieties, and the former's genetic diversity level was better than varieties.Thirty Ixeris polycephala materials were separated into six groups based on UPMGA clustering analysis, the first group included six varieties and eighteen cultivated new lines, the wild materials were divided into others groups, clustering analysis and principal component analysis results was relatively consistent. Comprehensive results showed that Ixeris polycephala groups have abundant genetic variation, there was close genetic relationship between cultivated new lines and varieties.4. Construction DNA fingerprinting of Ixeris polycephala varieties (lines) baesd on EST-SSR and SRAP markersWith the intention of DNA fingerprinting construction among 14 Ixeris polycephala varieties (lines), twenty four of 152 EST-SSR primers and 32 of 209 SRAP primers were screened according to clear bands and high polymorphic imformation.Total of 270 bands including 223 polymorphic bands had been amplified from 24 EST-SSR primers, the polymorphism information content values reached 0.834.The Nei's gene diversity (H) values ranged from 0.2464 to 0.4288,and the Shannon's information index (I) values ranged from 0.3597 to 0.6148, the distinguished varieties (lines) number ranged from 3 to 14. Thirty two SRAP primers detected 367 polymorphic bands and the average value of polymorphism information content was 0.826.The Nei's gene diversity (H) values ranged from 0.2006 to 0.3898. and the Shannon's information index (I) values ranged from 0.3167 to 0.5716. the distinguished varieties (lines) number ranged from 2 to 12. Nine varieties (lines) emerged special bands on 7 primers, and took comprehensively consideration of each genetic diversity index, obtained a total of 40 polymorphic bands from 5 core primers (IpSSR102?IpSSR80?IpSSR91?Me10+Em5?Me9+Eml7)for DNA fingerprinting construction of 14 Ixeris polycephala varieties(lines), and each varieties(lines) had a standard DNA fingerprinting pattern.