| Lilium spp.is a world famous perennial bulbous flower with high ornamental value.It can be divided into single-petal lily and double-flower lily according to its flower type and quantitative characteristics.With the improvement of people’s consumption level and cultural pursuit,single-petal cultivar will inevitably cause aesthetic fatigue in the market.But at present,there is few double-flower resource in China and the research directions are not deep enough,which lead to relatively less quantitative production in the market.In order to effectively promote the regulation of flowering period and breeding of improved cultivar of double-flower lily,this experiment used the single-petal cultivar ‘Love Story’,‘Sunny Keys’,‘Curie’ and double-flower cultivar ‘Elena’,"Natalia’,‘Talia’,‘Harvest 33’ and‘Harvest 603’ as materials respectively.By analyzing and comparing the flower bud differentiation process and chromosome karyotypecharacteristics,it aimed to provide a theoretical reference for further understanding of the formation of double-flower lily organs,genetic information and genetic relationships,and then to explore the mechanism of double-flowering.The research results were as follows:1.The results of paraffin section showed that the sequence of flower bud differentiation of the double-flower cultivar of Oriental Lily ‘Natalia’and ‘Harvest 33’ was still centripetal,and the process can be divided into undifferentiated period,inflorescence primordium differentiation period,small flower primordium differentiation period,primitive petal differentiation period,alienated petal from stamen differentiation period and pistil differentiation period,of which the characteristics of the first four periods were similar to the single-petal cultivar ’Love Story’.Alienated petals from stamens and the pistil due to morphological difference compared with single-petal cultivar,the differentiation and development had their own characteristics and there was a possibility of a normal stamen alienating into 2 to 3 petals.‘Natalia’ and ‘Harvest 33’both completed flower bud differentiation within 40 days,while it took‘Love Story’ approximately 45 days to finish.2.In the climatic condition of Nanning,the average life cycle of the five double-flower cultivar for test was 110.4d,shorter than the 121 d of single-petal cultivar,and the average plant height was 98.8cm,which was higher than the 51.6cm of single-petal cultivar.The flower diameter wasabout 19.7cm,which was smaller than the 21.3cm of the single-petal cultivar.The number of petals of a single-petal lily was constant at 6,while that of double-flower cultivar generally varied from 18 to 24 depending on the variety.Observing the mature flower organs of‘Harvest 33’,it was found that the stamens of double-flower cultivar were missing,homologously transforming into alienated petals,the three carpels were obviously not healed,and there was no enlarged stigma.3.The ultra structure of mature petals and stamens of single-petal cultivar ‘Curie’ and outer alienated petals and inner alienated petals of double-flower cultivar ‘Harvest 33’ of Oriental Lily were observed by scanning electron microscope.It was found that the arrangement,shape and texture of epidermal cells were in a certain gradual relationship,from the stamen of single-petal cultivar to inner alienated petal and outer alienated petal of double-flower cultivar to the petal of single-petal cultivar.The epidermis changed from a complete long strip arrangement to an irregular arrangement of cells,and the arrangement became sparse gradually,and the morphology of a single cell increased gradually.From inner and outer alienated petal of double-flower cultivar to the petal of single-petal cultivar,the skin texture gradually changed from smooth and flat to fold.To a certain extent,the gradual relationship further confirmed the possibility that the alienated petal of double-flower cultivar are derived homologously from the stamen.4.The results of chromosome karyotype analysis showed that the double-flower cultivar ‘Talia’,‘Elena’,‘Harvest 603’ and single-petal cultivar ‘Sunny Keys’ were all homologous diploids,2n = 2x = 24,the fluctuation range of double-flower chromosome asymmetry coefficient was 80.35% ～ 81.68%,the average value was 81.18%,higher than the74.41% of single-petal cultivar,and the karyotype of double-flower cultivar ‘Talia’ and ‘Harvest 603’ was type 4B while ‘Elena’ was type 3B,single-petal cultivar ‘Sunny Keys’ was type 3B.The evolution grade of double-flower Oriental Lily was higher than that of single-petal Oriental Lily,and the variation of karyotype may be one of the indirect reasons to promote the double-flowerization of lily petals. |
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