Variation Of Lignin Content And Association Analysis Of FmPAL Nucleotide Polymorphism In Progenies Of Fraxinus Mandshurica Interspecific Hybrids

Fraxinus mandshurica is one of the most important wild protected plants in Northeast China.In this study,the variation of lignin content in F1 progenies of interspecific hybrids of Fraxinus was analyzed.Phenylalanine ammonia lyase(PAL),a key enzyme in lignin biosynthesis pathway,was cloned.The bioinformatics and expression pattern of FmPAL gene were analyzed.The SNP loci of FmPAL in F1 clones were screened and correlated with lignin content,which laid a solid foundation for molecular breeding and wood improvement of Fraxinus mandshurica.The main results are as follows:1.There were significant differences in lignin content between 71 hybrid combinations of Fraxinus mandshurica and 16 free-pollinated progenies of female parent(P<0.01).The coefficient of variation of each cross combination ranged from 17.27%to 24.43%.The heritability ranged from 0.657 to 0.801.The hybrid combinations with highest lignin content were-No.70,No.129 and No.7.The genetic gains of lignin content were 13.59%,25.57%and 36.33%,respectively.Six clones with high lignin content were selected as follows:1-86-5,1 1-100-3,11-129-6,11-7-10,1-48-4 and 1-55-1.Significance of growth traits(growth rate/basal diameter)of grafted seedlings of 81 hybrid combinations of Fraxinus mandshurica and 19 free-pollinated progenies of female parent was analyzed.There was no significant difference in the height growth and the basal diameter of free pollinated offspring of female parent and.The coefficient of variation of the growth among the hybrids ranged from 67.94%to 74.22%.The hybrids with the highest growth were 69,75 and 112.The genetic gains of growth and basal diameter of 69 hybrid combinations were 47.09%and 5.45%respectively.those of 75 hybrid combinations were 34.75%and 24.15%respectively.those of 112 hybrid combinations were 61.54%.2.The FmPAL gene was cloned and its coding region was 1674 bp,encoding 557 amino acids.Using bioinformatics analysis and expression pattern analysis,we showed that FmPAL protein was a stable hydrophilic protein with no signal peptide but transmembrane domain.The protein of Fraxinus mandshurica had close genetic distance with Pinus sylvestris var.mongolica.The results of expression pattern analysis illustrated that FmPAL had the highest expression in new shoots,and reached the highest expression level in May.During abiotic stress and hormone induction(low temperature,salt,abscisic acid,auxin and gibberellin),the expression of FmPAL gene changed significantly.The results showed that FmPAL gene was involved in abiotic stress and plant hormone signal induction.3.Single nucleotide polymorphism(SNP)of FmPAL gene was studied in 176 clones of Fraxinus mandshurica F1 generation.A total of 33 SNP loci were obtained by sequencing.The PI value of nucleotide diversity was 0.00745,the haplotype number was 131,the haplotype diversity value was 0.9997,and the average difference of nucleotides was k:12.423.It is proved that FmPAL gene has high mutation rate and rich genetic diversity.The single SNP base was genotyped according to the sequence peak map.The correlation between wild homozygous and mutant homozygous lignin content was analyzed.Three SNP loci were screened out,which had significant differences with lignin content.The results showed that SNP 140,SNP654 and SNP796 in FmPAL gene were significantly correlated with lignin content in Fraxinus mandshurica.