| Dactylis glomerata L.also known as Cocksfoot or orchardgrass,belonging to the genus Dactylis of the Gramineae.With the high-yielding,strong adaptability,high sugar and protein content,and persistence,orchardgrass has been became one of the top three perennial forage grass grown worldwide for more than 100 years.In addition,orchardgrass also plays an important role in the ecological engineering and pasture construction,and the demand is very great.Therefore,it is very important to breed new varieties of orchardgrass with high quality and adaptability.Due to highly cross-pollinated,orchardgrass is highly hybrid in hybridity.Like other most grass,orchardgrass yield related traits were quantitative trait controlled by polygene and affected by environmental and management factor.It is difficult to meet the requirements of cultivating new varieties of Dactylis glomerata by using conventional breeding methods.The genetic map of orchardgrass could be used for locating important agronomic traits,further providing basis for gene mapping and cloning,so as to improve the accuracy for breeding work.In this study,based on the proposed test-hybridization strategy,an F1 population of 214 individuals derived from the cross between two Chinese orchardgrass cultivar "Kaimo" and "01436" was used for map construction.In order to obtain a high density genetic map of tetraploid orchardgrass previously established,we used EST-SSR and genomics-SSR markers to enhance the density of the genetic map.Phenotypic detection was collected for this hybrid population,and then QTL analysis based on high density genetic map.It can help us to improve the selection efficiency for good genotype of yield and provide basis for molecular assisted breeding of tetraploid orchardgrass.The results of the study are as follows:(1)Density-increasing of Ochardgrass Genetic Linkage Map.574 pairs of EST-SSR markers and 150 pairs of Genomic-SSR markers were selected as the screening primers.A total of 169 clear bands were obtained,and 89 were used to construct the genetic linkage map of orchardgrass.A high-density linkage map of orchardgrass was constructed using 2,551 markers,which were distributed on seven linkage groups spanning 758.4 cM.The encrypted map including 4187 SNP markers and 84 SSR markers,the number of markers in the LGs from 166 to 709,with average 364.LG1 contains the largest maker with 709,while the LG7 was the least with 166 The sizes of the individual LGs ranged from 60.28 to 147.09 cM,with average inter-marker distances ranging 0.19—0.76 cM..The average distance between adjacent distance markers was reduced from 0.37 cM to 0.3 cM(2)Phenotypic identification and correlation analysis of related traits of orchardgrass.Phenotypic identification of population and parental in Ya’an from 2013 to 2017 and 2016 to 2017 in Chongzhou in the field in the full-bloom stage,including plant height,flag leaf length,flag leaf width,inverted two leaf length,inverted two Ye Kuan,stem diameter,inflorescence length,tiller number and dry weight per plant.Most of the traits between parents showed significant differences at 6 year points.The performance of the female parent "kaimo" is better than the 01436" of the male parent.The phenotypic values of most traits are within the range of paternal variation.Histograms and normal distributions of the frequency distribution of most traits showed that the data of all the years showed the normal distribution of continuous variation as a whole,which was in line with the genetic traits of quantitative traits and could be used for QTL mapping.Correlation analysis showed that most of the yield-related traits such as plant height,flag leaf length,tillers were significantly positively correlated with dry weight except for the flag leaf width,second leaf width and the stem diameter of YA2017,CZ2016 and CZ2017.The relationship with dry weight per plant were tillers,plant height and leaf length(3)QTL analysis of biomass related traits using an ultra-high-density genetic map in orchardgrass.MapQTL5.0 was used to conduct logarithm of odds and percentage of phenotypic variance explained analysis,and interval mapping(IM)was used to detect QTLs for target traits.The result shown,a total of 144 QTLs were identified and distributed on 7linkage groups with genetic contribution range in 5.7%～24.7%.Among them,the number of QTL of a single trait range from10 to 29,and the QTL with a contribution rate of more than 10%has 41,of which 4 are greater than 20%,and the number of Pleiotyopican and Multiple QTL was 13,9 respectively Moreover,he numbers of controlling Plant height,Flag leaf length,Second leaf length,Flag leaf width,Second leaf width,Stem diameter,Inflorescence length,Tiller number,Dry weight per plant 20,29,11,11,10,14,19,17,10 respectively.Most QTL can only be expressed in a single environment.At the same time,a QTL enrichment area was detected on 1,2 and 5 linkage groups,and the characters in each enrichment area were different. |
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