Ornamental Evaluation Of Willow Based On Leaf And Branch Characteristics And Identification Of Ploidy

Willow is recognized as general term of Salix and Chosenia which are members of the Salicaceae family.The genus Salix comprises more than 520 species,of which there are 257 species,122 varietas and 33 formas in China.Willow has many excellent properties such as easy breeding,fast-growth,good ornamental and strong adaptability.It is widely used for it can beautify and improve the natural environment,provides the fine materials and a variety of forest by-products.Willow,as a kind of evergreen tree species,widely used in plant landscape,is ideal tree species for road greening,scenic spot construction ideal,plain lake area afforestation and so on.Currently willow is used with a single variety in landscape application in the Beijing area,basically dominated by common species such as S.matsudana and its variant.Willow varieties or clone has not been fully excavated and utilized.It is difficult to meet the demand of landscape engineering.In this study,taking common willow clones adapted to Beijing area as the object,we established analytic hierarchy process structural model of ornamental judge based on willow leaf and branch characteristics,and evaluated the ornamental value of willow clones,and identified its ploidy by flow cytometry and root chromosome counting method,to provide scientific basis for the ornamental evaluation of willow and the selection and breeding of excellent germplasm,to lay the foundation for the development and application of willow germplasm resources.The main research conclusions were summarized as follows:(1)Ornamental evaluation model based on willow leaf and branches characteristics by using the analytic hierarchy process was reasonable and practical,which could quickly screen out the high ornamental value of willow clones.The system was divided into three layers.The first layer was the target: willow clones ornamental judgment;the second layer was criteria,including the leaves(C1)and branches(C2);the third layer was factor,the characters embodied criteria layer and was representative to willow ornamental judge.Mature leaf color,leaf shape,young leaf color,lateral branches color and twigs color were major factor affecting willow ornamental value.(2)Among 20 species of willow clones,S.Chaenomeloides var.iegata,SH31,S.erioclada,S.matsudana,S.babylonica,S.×Jiangsuensis CL.‘799',S.×aureo-pendula belong to Grade?,ornamental value was highest,branches and leaf traits characteristic was outstanding,can be applied in landscaping.(3)Flow cytometry experimental select Galbraith's nuclear isolation buffer as an extract,known diploid S.integra as comparison,test results show that G7,S.chaenomeloides‘Variegata' are diploid;SH31,S.cheilophila,are triploid;S.matsudana,S.capitata,S.matsudana f.lobato-glandulosa,DQ1,S.×aureo-pendulaCL.,S.babylonica,S.×chulbeozhv.Tu,S.cheilophila are tetraploid;S.×JiangsuensisCL ‘799',bamboo willow are hexaploid.(4)Take method of root tip tabletting to count willow chromosome number,the results showed the use of root tip tabletting obtained results were consistent with the results obtained by flow cytometry ploidy,it was fully confirmed that identification of willow ploidy by flow cytometry were reliable.In this study,the evaluation model based on willow leaves,ornamental branches characteristic by analytical hierarchy process could reflect willow ornamental objectively.The willow chromosome ploidy were identified by flow cytometry,and the application of chromosomes counting confirms the accuracy of flow cytometry.It provided a reference for the ornamental evaluation of willow and its application in garden,and laied the foundation for take full advantage of excellent germplasm resources to carry out crossbreeding.