Genetic Characteristic On Morphological Traits Of Eucalypt Interspecific Hybrids

As an important fast-growing timber tree,crossbreeding has always been an important method in the genetic improvement of Eucalypt.However,because of the lack of deep understanding of the genetic mechanism and variation characteristics of different traits in Eucalyptus interspecific hybridization,the efficiency of breeding is affected.In this study,Eucalyptus urophylla,Eucalyptus pellita,Eucalyptus tereticornis and their hybrids of plantation tree species in South China were researching materials,and the characteristics of leaf,fruit,bark and the genetic variation between parents and progeny were studied..The near-infrared spectra of the hybrids ' parents and their progeny and their reliability in the study of genetic characteristics were studied for the development of Eucalyptus hybrid breeding theory and the realization of the precise compounding of Eucalyptus hybrids.The results showed that:(1)In the leaf characters,there were significant differences between E.urophylla,E.pellita and E.tereticornis,but the similarity between E.urophylla and E.pellita was high,and the difference between them and E.tereticornis was great,which is consistent with the genetic relationship between the 3 species.The values on the leaf characters of the E.urophylla × E.pellita and the E.tereticornit×E.pellita were no significant difference with their male parent,but their had some significant differences with their female parents.The main characteristics of the hybrids between E.urophylla and E.tereticornis were derived from E.urophylla,but there were higher frequencies of transgressive phenomenon in quantitative and qualitative traits.The principal component analysis indicated that The leaf length-width ratio,the shape factor,leaf positive and negative color and the leaf wax could be used as the main distinguishing traits of Eucalyptus and its hybrids in the leaf characters.(2)There was a great difference between the narrow sense heritability and the broad sense heritability of all the traits,that was,the heredity of leaf traits were affected by the interaction between parents.The heredities of leaf length-width ratio,petiole length,leaf color and wax were mainly influenced by female parents,and the heredities of leaf area,leaf length and perimeter were mainly influenced by male parents.And the hereditise of leaf orientation,petiole shape and leaf apex were influenced by environment greatly.(3)In fruit traits,3 parents species had their own unique characters,the differences among of them were more obvious.In most qualitative characters,the values of the fruits traits of the E.urophylla × E.pellita,E.urophylla × E.tereticornit,E.tereticornit×E.pellita and E.tereticornit×E.urophylla were in the middle of the values of parents.But in the most quantitative,E.urophylla × E.pellita was similar to the male parent(E.pellita),the values of E.urophylla × E.tereticornit were slightly more than the parents',and E.tereticornit×E.urophylla had superior performances only in the fruit vertical diameter and transverse diameter.In the reciprocal cross combinations of E.urophylla and E.tereticornit,there were great effects on the size of fruit and carpopodium length.At the same time,in the hybrid family,the different characters of fruit had great differences,which indicated that the heredities of fruit size were influenced by parents' interaction.(4)In the bark traits,the appearence of hybrid offsprings of E.pellita and other Eucalyptus were nearly same as E.pellita.The traits of hybrid progeny of E.urophylla and E.tereticornit were consistent with the E.urophylla,and the parental reversal had no effect on the inheritance of bark traits.The characters of bark in each hybrid families were consistent,which showed that the heredities of bark traits were more stable.In addition,the trait of the way of bark exfoliation is closely related to the trait of the persistent skin.(5)NIRs information can correctly reflect the genetic data of different genotypes,successfully used in the qualitative discrimination of Eucalyptus hybrids and purebred,so it can also be used to evaluate forest tree gene flow.Combinating models with the SIMCA and PLSDA for the identification of Eucalyptus hybrids was more meaningful to improve the genetic improvement of Eucalyptus.In conclusion,the variations of Eucalyptus and its hybrids among leaves and fruit characters were more abundant,but the variations among bark characters were small.According to the different combinations of hybrids,each traits would exhibit different genetic characteristics.Therefore,in the improvement of directional breeding,different mating strategies should be formulated according to different hybridization types.The application of these laws can reduce the randomness of breeding and improve the efficiency of breeding,which was of great significance to the orientation breeding of Eucalyptus..In addition,the near infrared spectroscopy can be used as a fast and accurate tool to study genetic relationship of breeding materials.