|Summary:||碩士 === 國立中興大學 === 園藝學系所 === 103 === The present research aims to obtain the mutants with fertility of novel poinsettia cultivars by colchicine treatment, then used as pollen donor to cross with E. pulcherrima. We investigated the flowering physiology and pollen viability in Euphorbia pulcherrima and its endemic relatives ex. Euphorbia cyathophora, E. formosana, E. fulgens, E. jolkini, and E. leucocephala. It also assesses the possibility of individual hybridization between E. pulcherrima and other species or colchicine mutants. Moreover, the factor of cross barriers were also clarified and applied embryo rescue technique to resolve cross barriers to create desirable poinsettia progeny containing new Euphorbia germplasm.
After the treatment of different concentrations of colchicine in poinsettia interspecific hybrid cultivars, each with lanolin or with cotton, 3 polyploidy mutants were obtained from ʻDulce Rosa™’, 29 polyploidy mutants were obtained from ʻPrincettiaR-Hot Pink’, and 4 polyploidy mutants were obtained from ʻLuv U Pink™’.Furthermore, the fertility of ʻDulce Rosa™’ mutants and ʻPrincettiaR-Hot Pink’ were recovered, and the highest pollen germination rate was reached to 26.5%. It also obtained morphological difference mutants.
The bract color was observed in order to investigate the difference of between the poinsettia interspecific cultivars and their mutants in the epidermal layer and longitudinal-section of bract. Pigment concentration, amount of epidermal cell & epidermal layers each with a pigment, and the arrangement of epidermal cells all were related to bract color. Moreover, the forms of bract epidermal cell with onical or papillae cells observed by scanning electron microscope were also leaded to different colors of bract in poinesettia.
The result of this research shows that the anthesis of Euphorbia endemic species is as follows: E. cyathophora blossomed all year-round, E. formosana blossomed from March to October; E. fulgens blossomed from November to April of next year; E. jolkini blossomed from February to July; E. leucocephala blossomed from October to April of next year, and poinsettia commercial interspecific hybrid cultivars all blossomed from November to April of next year. The optimal sucrose concentration in Brewbaker and Kwack (1963) medium for pollen germination of Euphorbia species were 15%~20% and of poinsettia cultivars were 20%~25%. Moreover, the optimum temperature for pollen germination of Euphorbia species was 25℃ and poinsettia cultivars was 20℃.
The reciprocal crossing between poinsettia and Euphorbia species were also conducted. It couldn’t harvest mature seeds in the other cross combinations, only obtain progenies when E. cyathophora as maternal donor crossed with poinsettia, However, the progenies traits were similar to E. cyathophora, and the DNA content was exactly the same as maternal donor. The in vivo pollen tube was observed by fluorescence microscope, and the result indicated that the pollen tubes stopped only in the stigma surface tissue on the self-pollination of E. cyathophora, but the hybrid capsule still continued to enlarge, and also get mature seeds when the cross combinations between E. cyathophora with poinsettia as pollen donor.
Observed in vivo pollen tube by fluorescence microscope, the pollen tube could enter into ovule when the crosses between Euphorbia pulcherrima with Euphorbia species or the fertile mutants. This research also evaluated the efficiency of different cross combinations and period of day after pollination in embryo rescue, the results indicated that it were easier to regenerate when the section of ovule as expants which were obtained from the capsule on 26-32 day after pollination. The real hybrids were successfully obtained in present research which confirmed the relative DNA content by flow cytometry (poinsettia ʻSparkle Star’× ʻPrincettiaR-Hot Pink’mutant P-M13).