Preliminary Studies On Resistance Mechanism Of Tobacco Callus Inducted By Tribenuron-methyl

In recent years, herbicides were applied widely. The resistance of weeds came into being, and become serious. The problem became one of the center questions for discussion in the international weeds research. That the mutant preparation by screening handles a cell is horizontal in the cell be in progress. It cannot accept time, the space restricting, and handle large amount of group within shorter time, individual acquisition is had expecting properties.The method testing that tobacco (NC-82) is the project guiding material, making use of a cell with pattern plant originally, takes that the weed-killer benzene sulphur swells up as the medicament choosing, the profound benzene sulphur tobacco sifting take place resisting the more hurting organization and regenerates to plant. This paper studied change of seed vigor, root activity and chlorophyll contents after treated by tribenuron-methyl on regenerants. On the other hand, Taking the acetolactate synthase(ALS),which is the active target of tribenuron-methyl, plant important metabolic enzyme glutathione-s-transferase (GSTs) and the protective enzyme(SOD,POD)as experiment targets, for the sake of find the mechnaims of tribenuron-methyl. The results could be summaried as follows:1.Using tissue culture technique, embryonic callus derived from tobacco (NC-82) leaf were transferred to Murashige and Skoog (MS) media supplemented with median lethal concentration of tribenuron-methyl and selected for 3 generations. The resistant calli were cultured on horm one-free media supplymented with tribenuron-methyl and regenerants were induced.2. With the method of planting in pot, the tobacco regenerants that resistant to tribenuron-methyl were screened and regenerant seeds resistance ratio were determined. The results show that the identification of resistance potential indicated that the herbicide resistance of regenerant seeds increased, the resistance ratios were 3.18.3. The change of chlorophyll contents of sensitive variety and tolerant variety showed coherency trend after treated by tribenuron-methyl which decreased at first, increased later, and then decreased again, but the chlorophyll contents of regenerants variety is higher obviously than sensitivity variety. Nine days after spraying tribenuron-methyl chlorophyll contents of two treatments were higher than antithese obviously, which decline 75.2% and 82.3% respectively. Nine days later, chlorophyll contents of tolerant variety begin to increase again, while sensitivity variety kept decreasing.4. ALS activity of the sensitive variety is decreased than antithese obviously, the inhibition ratios was 34.6%. It may be one course that sensitive variety impressionable to tribenuron-methyl. Five days after spraying tribenuron-methyl, ALS activity of tolerant variety get maximum value which is 2.88 times to antithese .ALS activity of tolerant variety keep higther than it's antithese five days later. ALS activity begin increasing is one course for tolerant variety resistant to tribenuron-methyl.5. After spraying tribenuron-methyl in leaf, the GSTs activity of tolerant variety and sensitivity variety were decreased a bit, and then rise later gradually. Both treatments get maximum value five days later is 1.142 and 1.053 times of antithese respectively. The results showed that the detoxication ability of two treatments was strengthen and could metabolize tribenuron-methyl quickly. There are no differences of GSTs activity of tolerant variety and sensitive variety.6. POD activity of tolerant variety is higher than sensitive variety, which showed, that the tolerant variety has higher ability to clear away the H2O2. After spraying tribenuron-methyl in leaf, the change of POD activity of sensitive variety and tolerant variety showed coherency trend, which increased at first, decreased later, and then increased again. After treated 3 days, both treatments reach peak value and increase extent is 10.5% and 7.6% respectively.After spraying tribenuron-methyl in leaf, the difference of SOD activity of tolerant variety and sensitive variety is obviously. After treated 9 days, SOD activity of sensitive variety decreased clearly and decreased extent is 31.1% while the tolerant variety SOD activity increase extent is 43.1%.After spraying tribenuron-methyl in leaf, malondiadehyde (MDA) content of tolerant variety and sensitive variety both decreased at first, and then increased but there were no differences of two treatments. After treated 5 days, MDA content of the both treatments decreased and decreased extent were 18.6%and 12.6% respectively. MDA content of two treatments increase obviously after treated 9 days and increased extent were 29.1%and 45.2% respectively.7.By seed bioassay method, it was found that the surviving regenerant seeds vigor index and that of the control were 10.81 and 9.53, respectively. Peroxidase activity were 47.36 U·g-1·min-1 and 29.44 U·g-1·min-1,while acid phosphatase activity were 2.927 nmol·g-1·min-1 and 2.447nmol·g-1·min-1 respectively. The agronomic traits such as plant height, nod number in main stem, average leaf length, average leaf width and yield are not significantly different compared with control.8. The cross-resistance level of tobacco regenerants of resistant tribenuron- -methyl to other related herbicides were assessed by seed bioassay method. This result demonstrated it has apparently evolved resistance to Pyrithiobac-sodium, The relative resistance factors was 8.5. Which also had lower cross-resistance level with Thifensulfuron and Nicosulfuron, The relative resistance factors were 2.016 and 1.927.While lowest with Atrazine, The relative resistance factors was 1.175.