Analysis Of Genetic Diversity Of Peanut Germplasm Resources And AhLEA Gene Family

Peanut is an important oil crop and economic crop in China.More than 7000 peanut germplasms are preserved.However,it still lacks systematic collated identification,and the actual utilization efficiency is very low.At the same time,the lack of excellent germplasm resources and the excessive reliance on a small number of backbone parental resources are the main reasons limiting the breeding of new cultivars of peanut,especially the abundant disease resistance genes in wild accessions.So,the classification and sorting of peanut germ plasms is particularly important in the conservation of germ plasm diversity,the utilization of germ plasms,and the cultivation of new cultivars.In this study,94 peanut accessions at home and abroad were selected and collected to analyze the main traits of peanut.The phenotypic and quality data,principal component analysis,correlation analysis and systematic clustering analysis were performed,and SSR molecular markers were developed for evolutionary tree analysis and molecular identity card construction of these accessions.Bioinformatic and expression analyses of the Ah LEA-4 gene family,an embryogenesis enriched protein in late seed development,were also performed.The main findings are as follows:1.The coefficients of variation,PCA,correlation,and evolutionary tree analysis of phenotypic and quality data for the 22 cultivars of peanut were analyzed.The results revealed that the 22 material phenotypic traits were in the range of 0.14-0.48.The correlation analysis showed a highly significant positive correlation,which resulted in the classification of four principal components with a high cumulative contribution to87.35%.The range of variation coefficients for the quality traits of the 22 accessions was 0.12-0.77,and there were extremely significant positive correlations among some leaf related genes in the correlation analysis,which were classified into two categories by principal component analysis with a cumulative contribution of 83.60%,representing the majority of the information.Evolutionary tree analysis grouped the 22 accessions into three groups.Cluster I had one accession,z17,and was mainly characterized by a high main stem,a high number of main stem nodes,many individual pods,and small pods.Cluster Ⅱ had 12 accessions,and was mainly characterized by a short main stem,a low number of total branches,the lowest average number and fruit weight of individual plants,and the smallest oleic to linoleic acid ratio.Cluster Ⅲ had nine accessions,and was mainly characterized by an intermediate height of the main stem,the largest fruit weights of pods and individual plants,low crude protein and linoleic acid contents,and the highest oleic acid content.2.The coefficients of variation,principal component analysis,correlation,and evolutionary tree analysis of phenotypic traits in 67 wild peanut accessions were analyzed.The results showed that the largest coefficients of variation for phenotypic traits were for branch number and the smallest was for crude side branches.Correlation analysis showed a positive correlation between the number of main stem segments and branch number,and between the main stem height and main stem thickness.Principal component analysis grouped 13 traits into three with a cumulative contribution of64.88%,of which the leaf related trait eigenvector values were larger in the first principal component.The evolutionary tree analysis classified the wild species into three major groups.Six accessions were available in cluster I,and was mainly characterized by longer main stem leaves and more developed side branches.Cluster II had 26 accessions and was mainly characterized by short main stems and lateral internodes.Cluster III had 35 accessions and was mainly characterized by a high number of main stem segments and branches.3.Fifty six pairs of SSR molecular markers with high polymorphism and clear amplified bands were screened,and the observed allele number(NA)varied from 2.00-13.00;the average of effective allele frequency(NE)varied from 2.80;observed heterozygosity(HO)varied from 0.26 to 1.00;expected heterozygosity(HE)ranged from 0.16-0.92,with an average of 0.41.The variation of polymorphism information index(PIC)ranged from 0.08-0.81,and 32 pic values were greater than 0.5,indicating that the screened primers were of better quality.The 94 accessions were classified into two main groups by cluster analysis.Group I(pop I)had 42 accessions,containing all22 cultivars and 20 wild accessions.group II(pop II)contained 52 accessions,all of which were wild species,and was further divided into two subgroups(pop II A,pop II B)according to the node position of the evolutionary tree.Pop II A contained 24 accessions of wild species,and pop II B contained 28 accessions of wild species.Molecular identity cards were constructed for 94 accessions based on SSR primer polymorphisms,which will provide a foundation for germplasm identification and utilization.4.The Ah LEA-4 gene family,an abundant protein in late embryogenesis,was bioinformatically analyzed,resulting in a total of 10 gene members,all hydrophilic,throughout the whole peanut genome.Expression profiling of different tissues from peanut revealed that the Ah LEA-4 gene was constitutively expressed,with the 7 gene members most abundantly expressed in seeds at later stages of pod maturation and expressed in integuments,pistil,and stamen.Moreover,transcriptome analysis of Athe expression pattern under drought stress was simulated laboratory.The results showed that the relative expression of this gene in the roots and leaves of both materials showed an initial rising and then falling trend,and the expression was higher in the roots of A.monticola,which indicated that the expression of Ah PIX3 LG gene was induced by osmotic stress and was a stress inducible gene.