| Lotus belongs to Nelumbo(Nelumbonaceae),and has ornamental,cultural,economic,and ecological values.It is also an important material resource for plant phylogenetic research.China is an important country in terms of distribution and cultivation of Asian lotus(Nelumbo nucifera Gaertn.)and is rich in germplasm including cultivated cultivars and wild resources.The wild lotus germplasms are not only contain important genetic information,but also have the characteristics of usually large size of plants and flowers,and strong adaptability,as well as the advantages in specific nutrient contents,therefore they are important resources for the study of plant phylogeny and the breeding of new cultivars.Due to the influence of natural factors and the interference of human activities,the wild lotus resources are rapidly decreasing with the risks of decreasing genetic diversity and loss of important genes.However,the distribution and diversity of the wild Asian lotus resources has been poorly understood,and particularly the diversity and genetic relationship of wild Asian lotus resources in northern China are still unknown.To master the distribution and diversity of wild Asian lotus resources in northern China remain unclear.Therefore,it is not helpful for conservation and utilization of the wild lotus resources.In this study,the germplasms of wild Asian lotus were investigated in a wide range,and then representative populations were selected as experimental plant materials.The genetic diversity of the wild lotus in northern China was analyzed by combining morphological method and molecular markers,and its genetic background was investigated and identified.The main results included:1.Investigation and selection of the wild Asian lotus germplasm resources in northern ChinaFrom 2016 to 2017,the 24 wild Asian lotus populations(including 21 northern populations)in China were investigated for two consecutive years,and the data on the habitat status,population area,protection and utilization of the populations were recorded.It was found that northern China is an important region of the wild Asian lotus,among which Heilongjiang Province is the most concentrated.Judging from the habitat conditions,most of the wild Asian lotus populations in northern China were in natural growth without human’s interference.The 17 representative populations were selected for diversity analysis based on an criteria of documented literature,long-term natural growth,little or no human interference and morphological characteristics of wild lotus.2.Phenotypic diversity of the 17 wild Asian lotus populations in northern ChinaPhenotypic diversity of the 17 wild Asian lotus populations in northern China was analyzed based on the 25 phenotype traits.The results showed that the variation of 17 wild Asian lotus populations in northern China was relative low.The coefficient of variant(CV)for the 15 quantitative traits were from 4.97% to 26.51%.The CV values for leaf height,petal length and carpel number were more than 20%,namely 20.16%,20.55% and 26.51%,respectively.The Shannon-Weaver diversity index(I)for the 10 pseudo-qualitative traits were from 0 to 0.81.The I values for bud shape and petal shape were 0.81 equally.The bud shapes were ovate and the petal shapes were oval in most populations.The principal component traits were not obvious.The cumulative contribution rate of the first seven principal components was 76.634%.The main decisive traits included stamen number,carpel number,pedecile diameter,leaf height,petiole diameter,leaf length,etc.Some morphological differences were observed among populations,but they were not significant.The unweighted pair group method with arithmetic mean(UPGMA)clustering based on Euclidean distance could divide the 17 populations into three groups.The results of population clustering showed a certain correlation with the geographical location.Among them,14 populations,including HLJ-zy,NMG-kl,HLJ-fy,JL-hc,NMG-dx and SD-jn were clustered into one group;LN-xm and HB-ax were clustered into another group,and HLJ-hl clustered the third group.The clustering results of populations were related to the geographical location of the populations,and the populations with similar geographical location clustered together.The morphology and size of lotus fruits differed among different populations.The vertical-horizontal diameters raito of fruits in most populations from Heilongjiang,Jilin,Liaoning and Inner Mongolia,were larger,namely longer in shape,than those in Hebei populations,which suggested that they might be relatively primitive.3.Genetic diversity of wild Asian lotus in northern ChinaThe genetic diversity of the 69 wild Asian lotus samples from 25 collection points(populations)in six provinces including Heilongjiang,Jilin,Liaoning,Inner Mongolia,Hebei and Shandong Province were analyzed by the simple repeat sequence molecular marker(SSR)and the chloroplast DNA fragment sequencing,with 27 samples including wild Asian lotus from southern China,ancient Asian lotus,cultivars,wild Asian lotus from other countries and American lotus used as references.The results showed that the genetic diversity of wild Asian lotus resources in northern China was moderate.The chosen primers had good polymorphism,the 86 from 87 polymorphic bands were amplified using the 14 pairs of SSR primers(11 g SSR and 3 EST-SSR)in all 96 samples.The number of polymorphic bands(Na)amplified by each pair of primers was 3–15(6.143 in average).The average number of effective alleles(Ne),mean values of observed heterozygosity(Ho)and expected heterozygosity were 2.965,0.137 and 0.617,respectively.The values of Na,Ne,Ho and He of the wild Asian lotus in northern China marked by the 14 pairs of SSR primers were 4.701,2.504,0.087 and 0.552,respectively.The UPGMA clustering based on Nei’s genetic distance divided 69 wild lotus samples into three groups.GroupⅠincluded most of the samples from Heilongjiang and Jilin;Group Ⅱincluded most of the samples from Inner Mongolia and Fangzheng of Heilongjiang;Group Ⅲ included all samples from Hebei and Shandong,and the wild Asian lotus samples from southern China(except Wanning of Hainan).The results of UPGMA dendrogram based on Nei’s genetic distance and STRUCTURE analysis were similar.The results of chloroplast DNA fragments sequencing showed 16 haplotypes found in wild Asian lotus resources in northern China.The haplotype level of chloroplast was higher and the distribution of haplotypes in the wild lotus samples had geographical correlation.It is inferred that the genetic distance between the wild Asian lotus from the Songhua River basin and the Liao River basin in northeastern China was relatively small,and these lotuses were relatively primitive compared to those from other regions.4.Genetic diversity of wild Asian lotus populations in Baiyangdian Lake and Weishan LakeThe 127 samples including the two largest populations of wild Asian lotus in northern China(Baiyangdian Lake and Weishan Lake)and several reference materials were sequenced using RAD-Seq method,and the 535,269 SNP sites were obtained.The genetic diversity and genetic structure were analyzed based on the SNPs.The results showed that the populations differentiation between Baiyangdian Lake and Weishan Lake was not obvious but the intra-population genetic diversity of the two populations were relative high.Both populations showed external gene mixing.According the NJ phylogenetic tree,all the tested samples were divided into 10 branches,of which most of the samples from Baiyangdian Lake and Weishan Lake,6 wild Asian lotus samples from China,4 ancient lotus samples and the wild Asian lotus samples from Thailand and India were clustered into one umbrella branch.The results of NJ phylogenetic tree and population genetic structure showed high consistency.It is speculated that both Baiyangdian Lake and Weishan Lake populations had the same genetic background with the ancient Asian lotuses,and some wild Asian lotus populations from Heilongjiang,Jilin,Inner Mongolia,and so on.5.Comprehensive evaluation and conservation strategy of wild Asian lotus population resources in northern ChinaThe conservation and utilization values of 17 wild Asian lotus populations in northern China was analyzed using analytic hierarchy process(AHP),the results showed that the 17 wild Asian lotus populations were classified into three categories.Based on the habitat,genetic diversity and interference risk,the related protective measures were suggested respectively,and the corresponding protection suggestions were proposed.This study deepened the understanding of the diversity of wild Asian lotus resources in northern China,and preliminarily revealed their genetic and evolutionary relationship,which provided a theoretical reference for their protection,introduction,breeding,and landscape application. |
PDF Full Text Request