| Korean pine(Pinus koraiensis Siebold&Zucc.)is one of the tree species with high economic value for both fruit and wood uses in Northeast China.It is widely used in forest land renewal.Because of difficulties of P.koraiensis to reproduce asexually,the building of seed orchards has been the most important way used to improve this species.However,due to the slow growth of Korean pine,low degree of genetic improvement,etc.,part of the Korean pine seed orchards still in the primary stage,thus it is imperative to upgrade the seed orchards.In this study,110 different cloned parent genotypes and families(86 half-sib and 28 full-sib)of Korean pine at Naozhi orchard,northeast China were taken as experimental materials.Several morphological characteristics and SSR markers were investigated and genetic variation parameters were calculated.The results were as follow:(1)The analysis of variance in growth characteristics indicated that all the investigated traits(tree height,basal diameter,and diameter at breast height,diameter at 3-meters height,stem straightness degree,crown breadth,crown height,branch angle,and branch number per node,bark thickness,and stem volume)showed significant differences in variance sources(blocs and clones,at probability level Pr<0.0001).The coefficients of phenotypic variation ranged from 10.73%to 35.45%and clonal repeatability extended from 0.06 to 0.78.Four principal components retaining 84%of the total variation were extracted.The linear regression modal showed that tree height,diameter at breath height,and branch number per node brought significant information to explain the variability of clones in stem volume.Using extracted characters as selection index,eleven clones(PK105,PK104,PK59,PK28,PK36,PK102,PK109,PK101,PK14,PK47 and PK27)displayed highest Qi-values in a selection rate of 10%corresponding to the genetic gain of 42.96%in stem volume.(2)Based on 14 cone,seed and nut traits of 110 parent clones,the analysis of variance showed that all clones were significantly different in various traits(Pr<0.01).Phenotypic coefficients of variation and repeatability ranged from 9.1%to 34.4%and from 27.5%to 97.7%,respectively.Except for the cone layer and cone seed numbers,the other traits were positively or negatively correlated.Three principal components were identified.Seed and nut traits were the most important traits in the first principal component,and cone traits more important in the second.Using correlation and principal component analyses,cone number and other traits were selected to evaluate materials.Twenty-two clones were selected using a selection rate of 10%based on cone number independently or other combined traits.The genetic gain for different traits ranged from 6.2%to 24.3%.(3)Wood quality traits of 110 parent clones revealed significant differences among P.koraiensis clones and no significant difference in blocks.Negative weak correlations were observed between wood traits growth characteristics and among wood traits with each other,revealing negligible effect between these traits,suggesting a simultaneous selection of elite materials.Phenotypic variance was slightly lower and relatively high repeatability was observed in wood density,fiber length and fiber width at the clonal average values.11 elite clones including PK5,PK47,PK70,PK48,PK30,PK76,PK91,PK108,PK103,PK34,PK19 showed high performances in wood traits and were selected based on 10%of selection rate.(4)Growth and cone traits(tree height,diameter at breast height,volume,cone number,thousand seeds weight and single cone seeds weight)revealed significant differences(Pr<0.001)among Korean pine half-sib families,while no significant differences were detected among blocks and the interaction between blocks and families.The average family values for growth traits were 17.22 m,8.67 cm and 0.43 m3 for tree height,diameter at breast height and volume,respectively.The average cone number,thousand seeds weight and single cone seeds weight were 17.57 g,748.91 g and 77.25 g,respectively.Genotypic additive variance and phenotypic variances ranged from 0.00009 to 3.820 and from 0.0005 to 23.066,while genotypic and phenotypic coefficients of variation ranged from 2.693%to 37.196%and 4.963%to 60.595%,respectively.Heritability at the individual and family level ranged from 0.152 to 0.215 and 0.611 to 0.862,respectively.Growth traits were significantly positively correlated with each other,but cone traits showed a weak correlation with growth traits.Based on 10%selection rate,nine families each were selected as elite materials in terms of high performance in volume and cone numbers,with 22.16%and 43.82%genetic gain in volume and cone number,respectively.(5)Significant differences were observed among Korean pine full-sib families in growth characteristics including tree height,basal diameter,diameter at breast height,diameter at 3-m height,stem straightness degree,branches angle,crown width,crown height,branch number,volume and inter nodes distance between branch.Trait's coefficients of variation ranged from 6.072%to 56.250%.Moderate levels of additive genetic control were observed.Traits related to stem growth were highly positively correlated to each other whereas crown traits showed a weak correlation with stem traits.Based on multi-trait comprehensive analysis,six elite families and six excellent parents were selected,which resulted in a genetic gain of 5.6%,16.9%,and 36.4%in tree height,diameter at breast height,and volume,respectively.(6)Finally,110 Korean pine clones were found to be significantly different in compiled growth,cone,seed and nut phenotypic characteristics together.Most of the phenotypic characteristics showed great genetic variation among clones,while the genotypic differentiation was weak between the selection sites of clones.The SSR markers showed a relatively high level of genetic diversity(Na=4.67±0.43,Ne=2.916± 0.18,1=1.15± 0.07,Ho=0.69 ± 0.04,He=0.62±0.02,and mean polymorphic information content(PIC)of0.574),with higher heterozygosity as an indication of a lower probability of inbreeding events in the orchard.Despite weak correlation coefficients between dissimilarity matrices(r(A/B),range equal to 0.022,P-value<0.001),the genetic and phenotypic classifications congruently subdivided all the clones into three major groups.The patterns of phenotypic trait variations and genetic diversity are valuable to effectively select materials in breeding programs of P.koraiensis.In all,combining phenotypic traits and genetic markers in a genetic variation study(variation and diversity parameters)addition to classification analysis were of paramount importance to effectively orient the selection of producers and offspring elite trees in Korean pine seed orchard. |
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