| Maize (Zea mays L.) is one of the world’s three most important food crops and the most important feed crop, in China. the saline-alkaline soil is an important land resource in China. But the salt tolerance of maize is relatively poor. So the application of plant genetic engineering technology to cultivate the new varieties of genetically modified maize with drought salt tolerance is one of the effective ways to grow maize in saline-alkaline soil. In this study, two related experiments were carried out for this purpose, and following results have been achieved:1) The mountain spinach choline monooxygenase gene AhCMO was transferred into maize inbred line’Zheng58’by the ultrasonication-assisted pollen-mediated transformation approach, which proved that the method was an effective method for genetic transformation in maize.2) Transgenic maize progenies were evaluated for salt tolerance, and the transgenic maize plants were generally superior compared to the control plants. Two elite salt-tolerant lines were selected. The major research contents and results were shown as follows:(1) In the first experiment, the vector, plasmids pBin438, containing gene AhCMO were transferred into maize inbred lines’Zheng58’by the ultrasonication-assisted pollen-mediated transformation approach. Three hundred maize plants were pollinated with treated pollen, and87seed setting plants were harvested with276seeds obtained. The efficiency of seed-setting was29%. After the kanamycin resistance screening and PCR detection of the plants in T1generation,37positive maize plants were obtained. The transformation rate was approximately13.41%, and the PCR-positive rate of the T1generation plants was19.7%; the PCR-positive rate of the T2generation plants ranged45%～55%which is significantly higher than in the T1generation. This showed that the target gene of partial transgenic plants could be inherited to the next generation and tended to be stable.(2) In the second experiment, the non-transgenic maize plants were used as materials to select a suitable salt concentration for evaluating salt tolerance of transgenic maize plants, which was250mmol/L NaCl solution. Then, the salt tolerance of T3generation transgenic maize plants with positive PCR detection results was determined. Through observation on their growth status and measurement of morphological, physiological and biochemical indexes, the following results were obtained:①The morphological observation showed:Under the salt stress, the leaves of control plants gradually turned yellow, wilting and finally withered and died, while the transgenic plants grew normally; in addition, the root systems of transgenic maize plants were larger than that of their conterparts.②The morphological indexes measurement results showed:In0mmol/L NaCl solution, there was basically no difference on morphology between transgenic and control maize plants; with the increase of salt concentration, the growth of plants in both groups were affected, but the transgenic maize plants performed superior under the same salt stress. Under the treatment of250mmol/L NaCl solution, the plant heights of the transgenic lines (except line N36) were10.4%-33.6%higher than that of the control plants, the fresh weights of the former were17.5%-55.2%heavier than that of the latter, and the dry weights of the former were13.6%-82.4%heavier than those of the latter.③Determination of physiological and biochemical indices indicated that under the stress of250mmol/L NaCl, the activities of superoxide dismutase (SOD), peroxidase (POD) and chlorophyll content of transgenic lines were higher than non-transgenic control plants, their malonaldehyde (MDA) content was lower than non-transgenic ones. In transgenic lines, SOD activity was increased by2%-208%; POD activity was increased by22%-65%; chlorophyll content was increased by8%-61%and MDA content was decreased by3%-93%. Based on evaluation result, two of the five transgenic lines had salt tolerance levels scored three grades higher than that of the control. |
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