| Mesona chinensis, also known as Xian-Cao, Xian-Ren-Cao, Hei-Dou-Fu-Cao in China, is an annual herb belonging to the Labiatae. It chiefly distribute in southern China, India and Malaysia. It was a very important medicinal and edible plant with sweet flavor, cold, astringent; function on clearing heat, cooling blood, diuresis, and anti-oxidation,-aging and-tumor. Mesona grass is a widely used medicinal herb, can cure heat stroke, cold, hypertension, jaundice, kidney disease, diabetes, joint and muscle pain. Its market share has exceeded10billion yuan.The wild Mesona grass chiefly reproduce by perennial root underground. In winter when temperature below0℃, the aerial parts are frozen to death and it continue life with perennial root. At present, cutting propagation is its generally planting way. This planting way lead low reproductive efficiency and variety degeneration. Therefore, in this paper, the optimal rapid propagation technique system of Mesona grass were established with Wuzhou Mesona grass. On the basis of rapid propagation technique system, polyploid breeding of Mesona grass were studyed by using colchicine as polyploid inducing agent. The results showed as follow:1Rapid propagation techniques of Mesona chinensis:Stem segments were used as explants. And explants were dipped in75%alcohol for10seconds first; then sterilized in0.1%HgCl2for15minutes; subsequently rinsed five times with sterile water and cultivated in inducement medium; the survival rate was60%. The optimum shoots inducing culture medium was MS+6-BA0.5mg/L+NAA0.1mg/L. Subculture and clustered shoots multiplication medium was MS+6-BA0.3mg/L+NAA0.06mg/L+ZT0.3mg/L. And root inducing medium was1/2MS+NAA0.2mg/L.2Polyploid breeding of Mesona chinensis:(1) Polyploid Induction:with Mesona grass pots or tissue culturing seedlings as material, polyploid induction of Mesona chinensis was studied by using the drip method, the mixed culture method and immersing method. The results show that immersing method was the best. The optimum induction was immersing in0.01%colchicine solution for48h. The final induction rate reached16.6%. Microscopic observations of root tip chromosome found the chromosome numbers of diploid were2n=2x=32, and that of tetraploid were2n=2x=64. Besides, some chimeras were found during experiment. These chimeras can ultimately become homozygosis tetraploid after transfer and separation for several times.(2) Morphologic characteristics observation of polyploid:The diploid and tetraploid plants with the same growth conditions and phase were selected for leaf characteristics observation. The results showed that the tetraploid seedling stocky and growing slower. Length and width of tetraploid leaf were138%and139%of the diploid. And the leaf guard cells size of leaf guard cells reached152%and149%of the diploid. The number of chloroplasts in guard cells of tetraploid reached145%of those in the diploid. And the stomatal density of tetraploid was only63%of those of the diploid.(3) Physiological and biochemical comparison between diploid and tetraploid:The diploid and tetraploid plants with the same growth conditions and phase were selected to measuring the TTC contain in root; the content of soluble protein and soluble sugar in leaves, root and stem separately. The results showed that tetraploid roots were more active because of its TTC content were significantly higher than that of diploid. The content of soluble sugar and soluble protein of tetraploid were also higher than diploid in stems, leaves and roots. Results of analysis of variance showed that the difference of all these indexes reached a significant level. |
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