Study On Resources And Classification Of Azalea Cultivars In China

Rhododendrons cultivars refer to a group of plants with stable and distinguishable characters which are cultivated and artificial selected from species,subspecies,varieties,hybrids or forma of Rhododendron L...There are about 1000 species of Rhododendron in the world,which are widely distributed in Europe,Asia,North America and other continents.As one of the Rhododendron distribution centers,there were about 542 species in China,accounting for more than 50% species of the world.The richness of wild species has provided the best conditions for the cultivation of Azaleas.It also makes the Azalea cultivars become traditional ornamental flowers in China with the reputation of "flower of beauty".At present,the domestic study on Azalea cultivars was mainly focused on the investigation of wild species,morphological classification,ecology,distribution and plant chemistry and with few studies on the classification of azaleas and their genetic relationships.Therefore,this study attempts to explore the genetic relationship between wild species and Azalea cultivars,starting from morphological characteristics,also using molecular marker analysis.Guided by the "Dual Classification Method" and the "ICNCP",we tried to establish a new classification system of Azalea cultivars.The main results were follows: 1.Investigation and geographical distribution of Azalea cultivars in ChinaThrough field investigation,we've collected 404 Azalea cultivars in total.112 come from the Jinhua(Zhejiang),accounting for 27.8% of the total..And 84 come from Shenzhen(Guangdong),70 from Ningbo(Zhejiang),44 from Ji'an(Jiangxi),56 from Dandong(Liaoning).These accounted for 17.3%,10.9% and 13.9% of the total varieties respectively.There were also 20 cultivars from Ganzhou(Jiangxi),3 from Lushan Botanical Garden,And 8 from Zhangping(Fujian Province),accounting for 5%,1.7%,0.7% and 2% of the total.The Azalea cultivars were mainly distributed in the southeast and coastal areas of China.Liaoning,Shanghai and Jiangshu are the birthplace of Azalea cultivars,with a long history of cultivating.2.Morphological study of Azalea cultivarsWe've collected 404 Azalea cultivars for morphological analysis between Rhododendron species and Azalea cultivars.Our results show that the follwing morphological characteristics are helpeful to trace the parents of cultivars: life habit,attachment type of branches and flowers,development type of bud,hairs type of leaves,morphology of flowers,the texture and size of leaf,the spots of cylinder,shapes of calyx lobe,the number and length of stamen and pistil,etc.While the new features appeared during the cultivation mainly in corolla(connate?schizogenous),the number of stamen and pistil(definite number?indefinite number),color of flower(purity?transition color?complex color),types of flower(single?house-in-house?semidouble ?double),types of leaf(oval,ellipse,lanceolate?angular,round),color of leaf(green,reddish brown?variegated,edge),calyx(oval?lanceolate).Combined with the morphological analysis,12 following species of Rhododendron were identified as closely related to Azalea cultivars in China: Rhododendron mucronatum,R.yedoense var poukhanense,R.macrosepalum,R.kanehirae,R.indicum,R.scabrum,R.kiusianum,R.serpyllifolium,R.kaemferi,R.obtusum,R.simsii and R.molle.3.Construction of Azalea cultivars classification systemBased on the analysis of the characteristics of Azalea cultivars,combined with “Dual Classificatioon Method”,we preliminary determined the classification system of Azalea cultivars was include 2 grades: Alalea cultivars and Alalea cultivars group,which contained 6 cultivar groups and 87 Alalea cultivars.The designation of Alalea cultivars and cultivar groups followed the ICNCP.Alalea cultivars were named by its latin name directly,the cultivar groups were named by the morphological characteristics of the varieties.4.Genetic relationship between Azalea cultivars using ITS and psbA-trnH sequence markersThe ITS and PsbA-trnH sequences of a total of 27 samples(including 6 wild Rhododendron species,and 22 Azalea cultivars)were analysed.Results show that these two molecular markers can both effectively distinguish wild Rhododendron species from varieties.The phylogenetic tree based on ITS and PsbA-trnH sequences showed a closer genetic relationship between R.simsii and R.pulchrum and 22 selected Alalea cultivars,which was consistent with morphological classification.However,the ITS and PsbA-trnH sequences can not distinguish the genetic relationship between Alalea cultivars,which the support rate was lower than 60%.So it was indicated that the source of Azalea cultivars is complex,and it is impossible to reveal the their genetic relationship by relying on ITS and PsbA-trnH sequence analysis.5.New varietyA new variety was found in the investigation,which was named R.simisii‘Chinese Red'.The morphological characteristics were similar to R.simisii,the only differences were the globular umbel inflorescence.