| With the pollen-tube pathway after pollination, we took Hashi 5 as the receptor and another 3 tomato varieties (EA, Caruso and wild variety) as the donor of the exogenous DNA to breed tomatoes. In the experiment, the exogenous DNA was treated with radiation, laser irradiation and ultrasonication to break down the chromosome and enlarge variation range. With these methods, the quality of tomato was improved and the guide of theory of crop breeding was achieved.With the pollen-tube pathway, the exogenous DNA that had been treated with radiation was introduced into Hashi 5 after its pollination and its descendants were selected and researched unceasingly. The results showed that some apparent characters of receptor had been changed by expressing the external characters of donor which indicated that the foreign gene was expressed in the descendants. The dominant gene of donor was expressed with high ratio from D1 generation to D4 generation of the receptor and the fruit quality of descendants had also been improved. The method of introducing exogenous DNA into receptor had been proved efficiently in overcome the defect that the fine Dutch cultivar hard to cultivate in our country with the weakness of the variety of our country was surmounted by shift the superiority of Dutch cultivar to the native variety.The leaf shape and height of the descendants of receptor were analysed. Except some individual descendant, most descendants expressed the leaf shape of donor with high ratio which indicated that the gene of leaf shape of donor was expressed in most descendants, but the leaf shape was separated in a few descendants. The high ratio expression of apparent characters of donor in receptor illuminated that the foreign gene was introduced into tomato and expressed successfully.We carried out the second experiment with the technology of introducingexogenous DNA into tomato. The study showed that the method has well validity, wellreliability and well repeatability and the descendants have steady hereditary.We also took the wild variety as the donor of exogenous DNA to carry out the hybrid experiment to transfer the strong disease resistance of wild variety to the native variety and recomposed the genome and the result was also satisfied. So the technology of introduction of exogenous DNA into tomato after pollination not only feasible within species but also feasible in over-distance hybridism and excellent gene can been transferred to the cultivate variety.The peroxidase and cytochrome oxidase isoenzymes of donor, receptor and their descendents were analysed by gradient PAGE to detect the expression of foreign genes in the descendents on molecular level and the expression of leaf shape of donor in successive descendents was also studied. It was found that the two kinds of isoenzvme zymograms of most descendents were very similar to the donor but much different from the receptor, which is accord with the difference of their external characters (leaf shape and height). The similarity of two isoenzyme zymograms between descendents of receptor and donor and the expression of external characters of donor in descendents can be indicators of the success of introduction of exogenous DNA into receptor and the success of expression of exogenous DNA in the descendents. It also indicated that the pollen-tube pathway technique is an effective way to improve tomato and enrich breeding materials.At the seedling stage, the resistance of the disease of leaf mold of the descendants of receptor into which exogenous DNA had been introduced was tested with the EA, Caruso and Hashi 5 as the check. The test results indicated that the resistance of the disease of leaf mold of the descendants were stronger than the receptor which meant that the introducing exogenous DNA into tomato after pollination can improve the quality of original variety. The method of introduction of exogenous DNA after pollination by pollen-tube pathway is an effective approach in improving crops and enriching breeding materials which has... |
