| Freesia is a beautiful bulb flower in the family Iridaceae,with colorful flowers and pleasant fragrance.In recent years,many freesia cultivars have been introduced to China.However,corms of these new cultivars turned to be degrade in many aspects because of divergence in climate and region.Therefore,it is urgent to change the current situation by cross breeding.In this study,comprehensive analysis on pollen morphology,aroma components,SSR molecular marker,and breeding system were conducted to provide theoretical support for cross breeding in freesia.The main research results of this paper are as follows:1.Pollen morphology of 15 cultivars of freesia were measured and analyzed.The results showed that pollen of the 15 cultivars of freesia are all single and zygomorphic with far polar single groove germinating hole.The exine ornamentation of freesia intersperses spininess,and the surface of some cultivars has circular holes and circular markings.2.Headspace solid-phase microextraction(SPME)coupled to gas chromatography-mass spectrometry(GC-MS)was used for analysis of the aromas of 15 freesia cultivars.The results showed that 39 kinds of volatile components were detected in 15 freesia cultivars.The main components are terpenes and alcohols.The study found that the Linalool has low odor threshold and it is high content in most measured freesia cultivars.Thus,the monotonous aroma of freesia is due to lack of rich aroma components in the volatile matter.In the future,we should focus on enriching and improving other valuable flower aroma components such as Ocimene,Limonene,Myrcene and so on.3.Genetic relationship of 16 freesia cultivars were analyzed by SSR molecular markers.The 16 freesia cultivars were divided into two groups at genetic distance of 0.65.The first category is mainly composed of cultivars that bred by Shanghai Jiao Tong University School of agriculture and biology.The second category consist of all recent imported cultivars.The second groups can be further divided into two subgroups at genetic distance of 0.67: the first subgroups are basically red purple species and the second subgroups are all yellow cultivars.Based on the contents of pollen morphology,floral and molecular markers,it is preliminarily determined that yellow cultivars are closely related to the white,while the red purple cultivars are relatively distant in genetic distance.4.Through the field observation and experimental study,the flower structure and breeding system in freesia has been acquainted.The results showed that the stamen of freesia was closed to the lateral side of the style and about 2 mm shorter than the stigma.In addition,the stamen and gynoecium of freesia mature at different times,and the highest period of receptivity stigma was not synchronized with the peak stage of pollen viability.The OCI and P/O was 5 and 1614,respectively.Taking the results of the artificial pollination experiment together,percentage of fertile fruit of spontaneous pollination is lower than the artificial pollination,which indicated that the breeding system of freesia is facultative outcrossing.5.we evaluated the statistics of hybrid combinations and seed quality to provide guidance for future breeding of freesia.The results showed that the seed setting rate is very high among most imported cultivars and the seed quality of self-cultivated hybrid combination is good.The seed setting rate reached 100% in hybrid combinations of Shangnong Shenhuang as a hybrid paternal with imported cultivars or Gold River as male parent and self-cultivated cultivars as female parent.If these two cultivars are selected as hybrid parents,it might be better to combine the cultivars of imported and self-cultivated advantage together in the future. |
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