| Gerbera jamesonii Bolus, playing a key role in the flower market, is one of the most important cut flowers in the world and the main flowers with the advantages of production and export in Yunnan province. The flower breeding is mainly by virtue of foreign varaties in China due to its disadvantage of wild rescourse in gerbera.It is significant for the sustainable development of gerbera to create and protect the new varieties of independent intellectual property by using the advantage varieties as germplasm.In this study, we used two introduced varieties of gerbera, Gerbera jamesonii ’Dama’ and Gerbera jamesonii ’Cabana’, as the materials to develop germplasm innovation from tetraploid selection and double haploid population (MDH)construction. We created new varieties or breeding materials on the base of the two varieties, and to lay a foundation for new variety breeding of Gerbera. However, there is still no report relative studies in Gerbera.1. The selections of tetraploid plantsComparison of the diploid plants, the characters of polyploidy plants have more advantages. In order to obtain tetraploid or breeding materials, we used the callus and multiple shoots as the explants to induced the tetraploid plants by colchicines. According to the variation index of the appearance, we found when we used0.0.02%concentration of colchicines to deal with the Gerbera jamesonii ’Dama’ callus for36h, the mutational rate is up to26.3%and the death rate is10%. when we used the0.03%concentration of colchicines to deal with the Gerbera jamesonii ’Cabana’ callus for12h, the mutational rate is up to30.9%and the death rate is12.5%. When we used the0.6%concentration of colchicines to deal with the Gerbera jamesonii ’Dama’ and Gerbera jamesonii ’Cabana’ multiple shoots for3d, the mutational rate is60%and the death rates are18%and24%,respectively.On the base of observing the differences of morphology and the stoma, we successfully selected2strains of gerbera tetraploid plants (2n=4x=100) DC4-3and CC4-1by the chromosome number identified technology and purification. At the same time, we selected three pairs of primers, which can effectively distinguish the diploid and tetraploid plants, by the ISSR molecular marker-assisted. The ISSR detected results are consistent with the chromosome detection.In order to obtain the indexes of new variety breeding, we compared the shape, the main horticulture and agronomy characters, cold tolerance and disease resistance of the tetraploid plants with diploid plants. Summarily, the tetraploid plants show more advantage than the diploids.The comparison of horticulture and agronomy characters:Compared to diploid plants, the leaves of tetralpoid plants are thicker, greener and bigger. The stomas on the surface are bigger than the diploids, and the total stoma area in per leaves are increased. The flower of diameter is bigger and flower color is whiter in tetraploid of Gerbera jamesonii’Dama’than those of diploid plants. In addition, we found some double-head flowers on the field. The flowers color of Gerbera jamesonii’Cabana’ tetraploid are yellower, and the content of anthocyanin on the bottom of tetraploids are richer than the diploids.In addition, there are more polyphyll in Gerbera jamesonii ’Cabana’tetraploid than those of diploids. According to the RHS color chart, the flower color of diploid is’YELLOE GROUP B’, while the flower color of tetraploid is’YELLOE GROUP A’. The flower and flower stalk diameter of two tetraploid materials are increased obviously than the diploids.The comparison of cold tolerance:There are significantly differences between the tetraploids and diploids on the contents of soluble saccharide, malondialdehyde, SOD and chlorophyll-a under the stress of low temperature. The physiological indexes of cold tolerance in etraploids are superior to diploids. On the whole, compared with the diploids, the symptoms of frostbite and dehydration are lighter in etraploids under the cold stress.The comparison of disease resistance:by comparing the antiviral ability between the tetraploids and diploids plants after inoculated by the Phytophthora cryptogea, we found the average onset time in tetralploid plants is delay3d than the diploids, and the level of the Phytophthora cryptogea resistance is from MR to R. 2. The construction of MDH populationThe construction of double haploid (DH) population, which obtain by anther cultured, is-one of the main technologies for modern bio-breeding and germplasm innovation. But this technology is not fit for Gerbera jamesonii. In this study, in order to create more breeding materials of MDH, we used the hybrid varieties as the materials to construct the MDH population via the induction culture of female nucleus.We obtained12double diploid plants of Gerbera jamesonii’Dama’and7double diploid plants of Gerbera jamesonii’Cabana’by the direct induction and indirect induction methods. We used the period III ovules as the materials to induce embryoid chromosome doubling by colchicines. When we used05%concentration of colchicines to deal with the materials for2d,the ratios are16.7%and23.3%for Gerbera jamesonii ’Dama’and’Cabana’. According to the identification of soma, and chromosome, we successfully selected4haploid plants from the parents of Gerbera jamesonii ’Dama’(DDH1-4)and6haploid plants from parents of Gerbera jamesonii ’Cabana’(CDH1-6) by detected the leaf stomata, DNA FACS and chromosome number. The average chromosome numbers are2n=2x=50.The related characters among the identification of MDH lines are significantly differences in growth period, flower type and flower color. All the lines show abundant genetic types. we selected randomly15MDH plants from the lines of DDH2ang CDH6to comparate the indexes of leaf length, leaf width, leaf area, flower stalk diameter and flower diameter with the relative parents. The T test result showed that, except of DDH2lines, the indexes and the characters of all the other materials are poorer than parents. |
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