| Vaccinium is a genus of perennial deciduous or evergreen shrubs belonging to the Ericaceae family originating from North America. Its fruits are blue or red and shape varies according to different species. Because of its juiciness and nice flavor as well as rich vitamins and unique nutrition, it is of great value in terms of health care and medical treatment, it has been listed as one of world’s five healthiest foods by Food and Agriculture Organization of the United Nations (UNFAO). Its fruit and processed products are always in short supply for its special flavor and health care value.Vaccinium australe is native to the subtropics in southeast USA, along the marshland of the coastal and inland areas. It is resistant to moist heat, humidity and cold. The plant favors humid and warm climate and fits the subtropical climate, but there are few cultivars at present. The experiment took Vaccinium australe "3#" which is diploid as materials. It introduced into Chongqing many years ago. The plant displays strong stress resistance, fast growth and high yield, but its fruits are quite small. Meanwhile, polyploid plants are huge in size. The study attempted to obtain the polyploid Vaccinium australe "3#" by chemical induction, in order to cultivate new variety with large fruits and powerful adaptability in the tropical and subtropical areas.Vaccinium australe "3#" was treated with different concentrations of colchicine solution at different stages, in order to figure out the best inducing method and obtain polyploids. The tetraploid plants were obtained by detecting the morphological features and chromosome numbers. Comparative tests between tetraploid and diploid plants involving the biological features, resistance and karyotypes provided basic data for the polyploid breeding of Vaccinium. The main results are as follows:1. The study of selecting proliferation medium hormone when the induced shoot tips of Vaccinium australe "3#" were taken as explant showed that the improved WPM medium with0.15mg/L ZT as proliferation medium was better. The proliferation rate was3.5.2. We studied on different concentrations of colchicine solution at different stages and selected the best inducing method and optimal combination of concentrations and processing time. The results indicated that the survival rate was70%, the mutation rate was13.33%and the rate of tetraploid plants was6.67%with the treatment of0.1%colchicines for24h.3. Basing on the morphological features and anatomic study, the variant plants showed general characteristics of polyploidy, such as thicker stem, shorter internodes, thicker leaf, larger leaf area, deeper leaf color, smaller leaf index, larger guard cells and less stomata per unit area, as well as wider palisade and sponge tissue.4. According to the cytological study, the chromosome number of the tetraploid is2n=4x=48, while diploid is2n=2x=24. Most of the mutagenesis plants are chimeras whose chromosome number is between24and48, particularlly few octoploid cells.5. Comparative tests containing the morphological and physiological indicators between diploid and tetraploid showed that the content referring to chlorophyll, SOD, POD, proline and soluble sugar of tetraploid Vaccinium australe "3#" were higher than diploid, but the malondialdehyde was lower in tetraploid with significant difference. Tetraploid eaves’moisture content was slightly higher than diploid and yet their electrical conductivity and electrolyte leakage were inferior to diploid. Strengthened resistance and obvious changes between morphological and physiological indicators were found.6. The analysis of karyotypes of tetraploid and diploid proved that the chromosome number of tetraploid Vaccinium australe "3#" is48, the karyolype formule is K(2n)=4x=48=40m+8sm, belongs to "2B". The chromosome number of diploidy is24, the karyolype formule is K(2n)=2x=24=18m+6sm belonging to "2B". Therefore the tetraploidy and diploidy have closely similar karyolype and chromosomal morphology. |
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