Genetic Diversity And Associated SSR Markers For Agronomic And Quality Traits Of Tall Fescue (Festuca Arundinacea Schreb.)

Accompanied with the optimization and adjustment of modern agricultural industry structure, the grassland livestock industry has got great achievement, and greater amounts of herbivore, especially the increase demands of forage. Therefore, breeding new varieties with high yield, good quality, and well adaptability is urgent need to meet the rapid development of pastoral industry. Nowadays, the varieties of forage grass were limited, with lower production capacity and poor resistance, which could not meet the demands of pastoral industry, ecological construction, and environmental greening in our country. Tall fescue is an important cool season grass, which not only served as turfgrass, but also is an essential forage grass widely used in pasture. Unfortunately, researches on tall fescue germplasm were not systematic previously, and only focused on resources collection, evaluation and storage. Modern biotechnology took a new method in resource germplam research, and the localization of important gene loci was employed in plant breeding, that provided valid support both in theory and practice in genetic improvement.115 Tall fescue accessions with different origins were employed in this research, both the agronomic traits and quality traits were accessed and evaluated, and the excellent accessions were screened. Meanwhile, the genetic diversity of tall fescue accessions were evaluated using SSR molecular markers, based on the linkage disequilibrium mapping, association analysis was conducted to explore the important gene loci that associated with agronomic and quality traits. The obtained results were as follows:1. Significant differences were observed in phenological period among 115 tall fescue accessions. Emergence period of cultivars were the fastest, and the European groups was ranking the third, with 13 d differ. Tall fescue with early heading period and florescence period were observed both in America groups and Asia groups, and the European groups were in the last, with 14 d differ.2. Wide genotypic variations in agronomic traits among 115 tall fescue accessions were observed. Notably, the variation coefficients of PH, PD, SC, SCP, and SW were exceeded 20%. PH and PD in cultivars were lower than in wild accessions. Higher variations in all agronomic traits except BCS were observed in wild accessions with the same origin. The highest variation was observed in SCP of European groups, and the variation coefficient of Asia group comes second. Notably, the variation in SW of five groups were larger. These results indicated that, abundant of outstanding accessions were existed in tall fescue germplasm, which could be selected as the excellent accessions for cultivar improvement.3. Correlation analysis on main agronomic traits showed that, very significant positive correlation was observed between PH and SL, PD, SC, and SW; between SL and PD, SC, BCS, and SW; between PD and SC, and SW; between SC and BCS; significant positive correlation between SC and SW. In contrast, there was a very significant negative correlation between SC and SCP.4. Principal component analysis showed that the cumulative contribution rates of first three principle components were up to 82.816%, and covered most of the information of seven agronomic traits. SL, SCP, and BCS were assured to be the main traits for agronomical performance of tall fescue. Clustering analysis showed that no significant correlation between geographic distance and agronomic traits.5. Wide genotypic variation in quality traits was determined among 115 tall fescue accessions. The variation coefficient of main quality traits was as following:rude fat> rude protein>dry matter. The rude protein contents in cultivars were higher relative to Asia or Africa groups. These results illustrated the positive selection on rude protein contents in forage grass breeding process. Highest contents of dry matter and rude fat were observed in Asia group. Variation coefficients of dry matter contents in wild accessions were higher than in cultivars. Meanwhile, variation coefficients of rude protein contents in wild accessions except European group were higher than in cultivars. On the contrary, variation coefficients of rude fat contents in wild accessions except Asia group were lower than in cultivars.6. Correlation analysis showed that significant positive correlation between rude protein and dry matter contents; significant positive correlation between rude protein and rude fat contents; negative correlation between rude fat and dry matter contents. Correlation analysis between quality traits and agronomic traits showed that:there was a very significant negative correlation between dry matter contents and PH, PD, and SC; significant negative correlation between dry matter contents and SL, and SW; negative correlation between dry matter contents and SCP. Significant negative correlation between rude protein contents and SW was also observed.7. Fifty-one SSR markers associated with agronomic traits (PH, SL, PD, SW, SCP, BCS, and SC) were observed. Fourteen markers were associated with PH; twelve markers were associated with SL; eleven markers were associated with SW; eight markers were associated with SCP; eleven markers were associated with SC; only one marker was associated with PD. It is interesting to observe that 9 markers (M1, M2, M3, M4, M19, M35, M40, M54 and Ml93) were associated with more than two agronomic traits. Four markers (M1, M2, M35, and M54) were associated with BCS and SC; M19 was associated with PH and PD; M40 was associated with SCP and SW; M193 was associated with PH and SL; M3 and M4 were associated with BCS, SW, and SC. Notably, BCS (branch count per spike) was explained by four markers (M1, M2, M3, M4) exceeding 10%.8. Forty-one SSR markers associated with quality traits (dry matter content, crud protein content, crud fat content) were observed. Twenty-six SSR alleles were associated with crud protein. Six markers (M213、M214、M215、M216、M217、M218) were associated closely with crud protein. Twelve SSR alleles were associated with crud fat content, six SSR markers (M253、M32、M169、M168、M100、M29) were associated closely with crud fat. Four SSR alleles were associated with dry matter contents, and the association between M49 and dry matter contents were highest, with the maximum explanation. Meanwhile, one SSR marker (M100) was observed to associate with both crud fat and dry matter contents, with the genetic explanation 12.8% and 12.7%, respectively. Most of the explanation rate by SSR markers to the quality traits was above 10%.9. Fourteen SSR markers associated with both agronomical and quality traits were observed. Six markers (M213, M214, M215, M216, M217, and M218) were associated with crude protein and PH; M40 marker was associated with curde protein, SW, and SCP; M100 marker was associated with dry matter contents, crude fat contents, and SC. These identified marker alleles associated with agronomical or quality traits could provide important information for tall fescue breeding in future.