| Aquilaria(Aquilaria sinensis(Lour.)Spreng.)is the only basic source plant which can produce agarwood in China belonging to Thymelaeaceae,Aquilaria Lam.Hainan Province is rich in germplasm resources of A.sinensis andis the main producing area of domestic agarwood.The agarwood produced in Hainan is of high quality and deeply loved by Chinese and foreign in ancient and modern times.However,in recent years,the research on the germplasm resources of A.sinensis has found that the artificially cultivated varieties/improved varieties lack systematic selection.There are problems such as the germplasm resources of A.sinensis are different and uneven,as well as lack of systematic understanding ofthe population genetics of A.sinensis.The investigation found that there were only sporadic remnants of native wild A.sinensis,some new seedlings with high variability and special phenotypic traits were also found in Hainan province.These resources may be formed by natural hybridization or mutation,and it may also be caused by multiple asexual reproduction and grafting.Their origin and kinship remains unknown.Therefore,we used morphological and ISSR molecular markers in this study to analyze thephenotypic characteristics and genetic relationships of 51 resources,to provide data for the breeding and creation of new varieties/improved varieties of A.sinensis,and has contributed to the upgrading and adjustment of the industrial structure,to increase growers’ income and sustainable development of the world’s agarwood industry.The main findings are as follows:(1)Morphological analysis was carried out on 16 main leaf traits of 51 A.sinensisresources.The quantitative classification criteria and genetic relationship of the varieties were discussed by statistical methods such as general descriptive statistics,correlation analysis,principal component analysis and cluster analysis.Among them,the coefficient of variation of the numerical characters of A.sinensis leaves was12.54%-28.54%,and the range of Shannon diversity index was 0.098-1.778.(1)Thecorrelation analysis indicated that there was a significant positive correlation between leaf area and leaf length,leaf width and petiole length.Also the leaf length was found significantly correlated with the leaf width and petiole length.And between leaf abaxial vesicles(with or without)and the degree of secondary vein uplift(P<0.01).There is a significant negative correlation between the leaf length-width ratio and leaf area,leaf width,petiole length.Moreover between the leaf shape and the degree of secondary vein uplift,leaf abaxial vesicles(with or without).And between leaf apex and leaf abaxial vesicles(with or without)(P<0.01).The leaf width was significantly positively correlated with leaf thickness(P<0.05)and the leaf thickness was significantly negatively correlated with leaf length-width ratio(P<0.05).(2)The results of the principal component analysis indicated that the cumulative contribution rate of the first five principal components was69.9%,and the first principal component was related to leaf secondary vein characteristics(secondary vein bifurcation angle,intensity and uplift degree)together with the leaf margin undulation.The second principal component is related to leaf shape.The third principal component is related to leaf color and leaf length-width ratio.The fourth principal component is related to leaf symmetry.The fifth principal component is related to the length of leaf petiole.(3)The clustering analysis of phenotypic traits show that the Euclidean distance of 51 A.sinensis experimental ranges from 0.707 to 11.197.No.10 and No.12 has the smallest Euclidean distance of 0.707,indicating the closest genetic relationship;No.42 and No.51 has largest Euclidean distance of 11.197,indicating that the two cultivars has the least genetic relationship.At the Euclidean distance of 10.0,the 51 A.sinensis test varieties are divided into 4 clusters.(2)ISSR molecular marker research was:(1)In this study,amplification results showed that 85 bands were amplified by the 10 primers screened,with an average of 8.5bands were amplified per primer,of which 60 bands had genetic polymorphisms.(2)The genetic diversity analysis showed that the genetic similarity coefficient among 51 A.sinensis germplasm resources was between 0.6353 and 0.9647,the genetic distance was0.0359-0.4537,and the average genetic similarity coefficient was 0.7830.(3)Through UPGMA cluster analysis,the dendritic clustering maps of the germplasm of 51 A.sinensiswere established.At the genetic similarity coefficient of 0.80,the tested materials could be divided into sixgroups,a total of 16 accessions from No.1-9,No.13-17 and No.22-23 were grouped into group I;a total of 5 accessions from No.18-21 and No.24 were grouped into group II;a total of 15 accessions from No.25-39 were grouped into group III;a total of 9 accessions of No.40-48 were clustered into group IV;a totalof 3accessions of No.49-51 were clustered into group V;a total of 3 accessions of No.10-12 were clustered into group VI.(3)Comparative analysis of morphology and molecular biology: The results of comprehensive morphological and molecular biology studies found that the clustering results obtained by the two methods were not exactly the same.Among them,the most representative similarities are mainly manifested in No.10 and No.11 and No.12 in the morphological clustering map,molecular clustering map and population clustering map,which all show unique singleness,that is,they are clustered into separate groups at different genetic distances.Compared with other groups,the accessions of this group had the characteristics of leaf thickness,large leaf area and wavy leaf margins.The mutual confirmation of the three cluster maps showed that No.10,No.11 and No.12 are closely related and possibly the same germplasm.The main difference is that the germplasm clusters with similar phenotypic characteristics in the morphological clustering map are not classified into one groupin the molecular clustering.At the same time,the germplasm aggregated in the molecular cluster map was scattered in the morphological cluster map,which may be related to the occurrence of false positives.In this study,the analysis of leaf morphology and molecular biology of 51 A.sinensisresources found that in the utilization and breeding,theleaf thickness germplasms has the closest genetic relationship and can be classified as a separate category.The investigation provided a scientific data for the innovative utilization and classification of resources of A.sinensis. |
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