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  • Author or Editor: Man-Zhu Bao x
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Shennongjia mountain region is famous for its various kinds of species. Through one year's deep-going expedition in the area, lots of valuable plant species were collected, among them many are very useful and had not been used in landscape. Such as Arisaema lobatum var. variegatum nv. LuDiFei, Cremastra appendiculata var. fulva LuDiFei, Stylophorum lasiocarpum (Oliv.) Fedde, Sedum filipes Hems., Iris wilsonii C. H. Wright, Amaranthus caudatus L., Cotoneaster dammeri Schneid, Meconopsis quintupineria Regel., Lysimachia paridiformis Franch., Dysoma versipellis (Hance) M. Cheng, Adiantum pedatum L. and so on. Some genera are quite rich in this region, especially in Rosa, Sorbus, Cotoneaster, Lonicera, Impatiens, Aconitum, Gentiana, Adiantum etc. All these are marvelous material for direct appliance in garden and for breeding. There are many rare plants in the area, large communities of Davidia involucrata Baillon and Chimonanthus praecox (L.) Link were found during the expedition, and what interesting more is that various natural variations do exist in the communities. Detail description and evaluation were given to the important species, and some suggestions of protection and utilization were offered in the paper.

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A set of Petunia hybrida plants encompassing a range of ploidy levels was developed through colchicine-mediated induction of chromosome doubling. The resulting double-flower tetraploid plants were cross-hybridized with inbred single-flower diploid lines to generate F1 populations with segregation for ploidy level and flower type. The initial in vivo application of colchicine to seedling apical tips produced mixoploid plants of petunia at a high rate of efficiency. Thus, 95% of the shoot tips treated with colchicine for 48 h resulted in polyploid mutant plants, and no difference in this efficiency was observed using concentrations of colchicine between 0.2 and 2.0 mg·mL−1. Of the polyploid plants, 10% were found to be tetraploid and 85% were mixoploid (chimeric). Compared with their diploid counterparts, polyploid plants underwent reduced elongation growth during the first 2 weeks and had thicker stems and shorter internodes resulting in dwarfing of the whole plant. In extreme cases, very slow growth rates produced stunted plantlets. Polyploid plants also had larger, thicker leaves and, in some cases, the leaves that developed after 1 month of growth appeared seriously malformed. Octoploid plants were also obtained and these tended to have more extreme phenotypes. Pure tetraploid plants of double-flower petunia were isolated by the in vitro culture of explants from the initial chimeric tetraploid mutants. These were crossed with three inbred single-flower diploid lines (S1, S2, and S3) thereby generating F1 populations that showed segregation for flower type and ploidy level and included the generation of triploid plants. In the tetraploid plants, flower diameter and the number of flower petals were not changed significantly (P > 0.05) compared with the original diploid double-flower plants, but observation of the pollen grains revealed segregation for size consistent with the increased ploidy level. Analysis of the F1 progeny plants also indicated that chromosome number is not necessary but sufficient to cause the production of semidouble-flowered plants. Flower color and flower diameter were also analyzed in the F1 progeny and complex patterns of inheritance were inferred. In addition to single and double flowers, semidouble-flowered plants were also suggested to be generated by the hybridization of 2n or 3n pollen from the double-flower tetraploid plants with the single-flower diploid lines.

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