Volatile Components Analysis And Fertility Evaluation Of Six Fragrant Tropical Orchids

There is a big gap between the sales of flowers in China and the developed countries.This is mainly due to the backwardness of varieties,and excellent varieties are the key to the production of high-quality flower products.It is urgent to carry out comprehensive research and development of China’s endemic flower resources and further study the genetic diversity of flower germplasm resources.Our research group has been committed to the collection and breeding of tropical orchid germplasm resources for many years.Tropical orchid（Tropicalorchid）is a precious ornamental plant.More than 100000 hybrid varieties have been known and bred all over the world.In spite of this,the products are still in short supply.At present,most of the cultivated varieties of tropical orchids on the market are gorgeous but not fragrant.Therefore,the cultivation of aromatic varieties has become one of the main trends of orchid breeding in the world.However,because most of the original species of tropical orchids are not fragrant,only 7 of the 70 species of Phalaenopsis have been found,so the breeding of scented tropical orchids has not made outstanding achievements.In this study,based on the tropical orchid germplasm resources collected by the research group for many years,six species of nail orchid subtribe species with pleasant aroma and beautiful flower shape were selected,and the flower fragrance volatile components of these six materials were analyzed and identified.At the same time,the pollen viability and stigma receptivity of different wild orchids were analyzed and identified by TTC staining and benzidine-hydrogen peroxide method,and the chromosome morphology and number of the materials were analyzed by chromosome pressing technique,in order to provide theoretical guidance for the hybrid introduction,ex situ conservation and follow-up application and development of tropical orchid fragrance.The main results are as follows:1.Using Aerides rosea as material,the optimum pollen medium was selected:20%sucrose+20mg·L^-1boric acid+10mg·L^-1Ca Cl₂.It is clear that TTC staining is the best method for pollen staining.The pollen viability of six materials was determined by the optimum medium and the best staining method.The results showed that the pollen viability of the six materials increased at first and then decreased with the extension of flowering time.The pollen viability was the highest in the full flowering stage（8-12 days in flowering,4-6 days in Aerides rosea）,the lowest in bud stage（0-4 days in flowering,0-2 days in Aerides rosea）,and almost no vitality in the decline stage（18-20 days in flowering,8-10 days in Aerides rosea）.The pollen viability was the highest in the full flowering stage（8-12 days in flowering,4-6 days in Aerides rosea）,the lowest in the bud stage（0-4 days in flowering and 0-2 days in Aerides rosea）.The stigma receptivity of six species of tropical orchids also showed a process of no-weak-strong-weak-none with the extension of flowering time.Therefore,in addition to Aerides rosea,the other five materials should be artificially pollinated at 8-12 days of flowering,and should be pollinated 4-6 days after flowering.Theoretically,the seed setting rate of cross is the highest and the success rate of cross breeding is the highest at this time.1.The optimal chromosome pressing technique is as follows:the newly grown root tips of mature plants are taken from 8:50 to 9:00 in the morning,rinsed and treated with saturated p-dichlorobenzene solution or colchicine at 4℃for 4 hours,then fixed with Carnot’s solution（95%ethanol:glacial acetic acid=3:1）at 4℃for 4-20 hours,then dissociated with 1mol L-1 hydrochloric acid at60℃for 6 minutes,and finally stained 12min with modified carbolicacid compound red staining solution.Pressing and microscopic examination and observation and analysis.The results showed that the karyotype formula of Rhynchostylis retusa and Aerides rosea was 2n=2x=36m+2sm,and the karyotype formula of Acampe rigida was 2n=2x=32m+6sm.The karyotype formula of Vanda coerulea,Vanda esquirolei and Vanda brunnea is 2n=2x=34m+4sm.3.The experimental results show that the characteristic components of the six experimental materials are different,and the sensory experience is also different.Terpenoids are the main volatile components of Aerides rosea and Acampe rigida,esters are the main volatile components of Rhynchostylis retusa and Vanda brunnea,and terpenes and esters are almost half of Vanda esquirolei.The relative content of nerol in Aerides rosea is the highest,which is 64.76%,followed byβ-farnesene,which is 24.75%.The content of1-methyl-4-（1-methylene-5-methyl-4-hexenyl）cyclohexene is also high,which is3.91%.The content of tetradecyl acetate in Rhynchostylis retusa is the most abundant,accounting for 35.39%of all ingredients,followed by farnesol,with a relative content of 32.32%.Of all the volatile chemical components in Acampe rigida,the highest content is basil,which is 66.86%,which is 7 times that of the second one,and the contents of allicene and nerol are 9.42%and 8.42%,respectively.The relative content of benzyl acetate was the highest in Vanda brunnea（42.06%）,followed byβ-basil（24.96%）.The content of methyl benzoate was the highest in Vanda brunnea,accounting for 65.17%.These ingredients with different odors are mixed in different proportions to form the unique attractive flavor of these six materials.These six orchids all have a large number of high-quality aroma components,whether for selective breeding or cross breeding,they are excellent raw materials for flower fragrance introduction.