| The daylily(Hemerocallis spp.)has been widely used as garden plants for landscaping with various flower types and colors,strong resistance and good adaptability.The number of variety has reached more than 80000 via more than one hundred years of daylily breeding.Nowadays,due to long-term crossing between cultivars,the genetic basis of daylily was narrow.Further research on the cultivar genetic improvement has some difficulties and great breakthrough.Given this,the interspecific hybridization is an important and innovative method for new cultivar breeding in daylily.In this study,crosses between cultivars and the wild species were performed,and the offsprings of interspecific hybridization were obtained in daylily.The interspecific cross compatibility and how to overcome the crossing barriers were systematically studied,and the genetic variation of flower traits were analyzed and the pigment composition of different color petals was preliminarily determined.These research results will provide the scientific basis for genetic improvement and genetic variation in the interspecific hybridization of daylily.The main results were as follows:Pollen viability of 'Rosy Returns' was determined in fluid nutrient medium.The optimum culture condition was 25? and 3h,and the best culture medium was 100 g-L'1 sucrose + 60 mg·L-1 H3BO3+ 40 ng·L-1 CaCl2.The wild diploid species H.lilioasphodelus had the highest pollen viability(64.54%),and the lowest was the wild triploid species H.fulva(28.28%).The detection of stigma receptivity showed that except for the 'Stella de Oro',the other five cultivars had the strongest stigma receptivity at 9:00 a.m.on the first flowering day,and the longest duration was 'Pardon Me'.The cross compatibility between different ploidy daylily was studied.In the interspecific hybridization of diploid daylily,the average expand ratio of fruits was 48.02%,the setting rate was 31.57%,the seed number per fruit was 9.39,the sprouting rate was 80.07%,the average albino seedling rate in the offspring was 3.70%and the average survival rate of seedlings was 60.94%.The albino seedling rate in the offspring of double petal daylily was the highest,the average reached 10.47%.The setting rate of interspecific hybridization between diploid and tetraploid,and the triploid was used as the male parent and diploid used as the female parent,were both zero.When the triploid was used as the female parent and the diploid used as the male parent,the average setting rate of interspecific hybridization was 19.58%,the average sprouting rate in the offspring was 35.00%,the average albino seedling rate was 6.35%and the average survival rate of seedlings was 38.71%.The pollination barriers of interspecific hybridization in daylily mainly incorporated a variety of chromosome abnormal behaviors,which existed in the meiosis process of microspores,mainly including unequal bivalents,chromosome single bridge,lagging chromosome microkernel and non-synchronous division.These phenomena can lead to the formation of abnormal pollen grains at the later stage,ultimately affecting fertility.The fluorescence observation of pollen tube showed that the numerous abnormal growth phenomana existed in the interspecific hybridization of daylily,such as the pollen on the stigma can not germinate,if the pollens germinate,however,it could not continue to grow;if the pollens grew,however,it could not enter into the stigma;if pollen tubes entered into the style,however,it twines and reverse turns,and could not reach to the ovary;if the pollen tubes reached to the ovary,however,it could not reach to the ovule.After the pollination,the embryology observation showed that abnormal embryonic development mainly displayed that the double fertilization was not in the embryo sac;the embryo and endosperm were developmentally retarded;the endosperms develop normally,however,the embryo stayed at the globular embryo stage and was degenerated;the embryo was normal with no endosperm.In order to overcome crossing barriers,the main methods included:the reproductive disorder of flowering asynchronism has been overcome using the ultra-low temperature-80?to dry the storage pollens;the crossing barriers before the fertilization were solved using different pollination methods,and the hybrid seed setting rate can be increased by an average of 10%using the repeated pollination in the offspring,the daub of 0.1%NAA can significantly increase the expand rate of fruits and hybrid seed setting rate;the crossing barriers after the fertilization were solved using the method of the in vitro culture of immature embryo,the germination rate of the in vitro culture of immature embryo was more than 90%on the 30d,and could reach 100%on the 40d after the pollination,the optimal culture medium of hybrid embryo culture was MS+NAA 0.1 mg·L-1 + 6-BA 2 mg·L-1.The genetic variation analysis of botany traits were performed in the parents and offsprings of interspecific hybridization of daylily.The results showed that 20%individuals of the Fi hybrids exhibited higher flower diameter than that of the high-plant height-parent.and the highest was reached to 12.20 cm.When the cultivar 'Pardon Me' was used as the female parent,10%individuals of the F1 hybrids in inflorescence characteristic exhibited more than 17.7,and the highest was reached to 20.33.When the cultivar 'Double River Wye'was used as the female parent,which crossed with 3 single patal culyivars,the average petal numbers were all more than 6 in the offspring.However,the proportion was different in the offspring of double petal flowers,among them,the petal number of the offspring 'DF-11' was the most(12)in the cross of Double River Wye × FB.The results on the flowering phase showed that the secondary inflorescence characteristics could significantly extend the flowering phase of single plant in daylily.The parent which enjoyed secondary inflorescence characteristics was used as the female parent,crossing with the no characteristics of secondary inflorescence parent.The plants enjoyed secondary inflorescence characteristics were found in the offspring.Through the visual inspection,RHS Colour Chart and the measurement of colorimeter,the flower color of the offsprings of interspecific hybridization in daylily can be divided into 3 kinds of color scheme:yellow(yellow and orange),pink and red.The genetic analysis of flower color showed that the red 'Pardon Me' was used as the parent,whether crossed with the yellow,orange and pink parent,the proportion of red flowers were higher in the.offspring,which suggested that the hereditary capacity of red flowers were stronger.The distribution of flower colors was wide in the hybrid offspring,the results indicated that the flower color of daylily may be controlled by the interaction of multiple genes.The research on the petal structure and the diatribution of pigment were conducted in the 4 kinds of color of daylily,the pigments were distributed in the upper epidermis of petal,lower epidermis and palisade tissues in the middle in the yellow and orange daylily,and the pigments were mainly distributed in the cells of upper epidermis and lower epidermis in the pink and red daylily.In the dark red daylily,the upper epidermis has obvious conical projections,which increased the absorption of light.The preliminary qualitative analysis of the flower color was carried out in the 4 kinds of color daylilies,the results indicated that the petals of daylily contain 4 kinds of pigment,mainly including anthocyanins,carotenoids.The petals with green throat contained a small amount of chlorophyll. |
PDF Full Text Request