| Maize is an important food and grain feed crop in the world, which has been widely used in food industry, industrial processing, the development of new energy and other aspects. With the development of animal husbandry and industry, and the growth of world population, the status of maize in human life is more and more important. Therefore, improving the content and quality of maize is related to human health and economic development. Traditional ways of maize breeding mainly rely on cross breeding to improve the production and quality of maize, but the cycle of conventional breeding is long, and its genetic resources are limited, which greatly condition the development of maize breeding. With the rapid development of biotechnology, breeders begin to apply genetic engineering technology to improve the varieties of crops, and try to introduce the gene controling excellent traits into crops to breed new varieties with good quality and high yield, excellent stress-resistance, insect-resistance or disease-resistance. In the past 20 years, new maize varieties that have excellent traits such as insect-resistance, disease-resistance, stress-resistance and herbicide-tolerance have successfully been bred by using genetic engineering. Transgenic maize with insect-resistance and herbicide-tolerance has been widely planted, which effectively increased the maize yield and decreased production cost.In the practice of maize breeding by genetic engineering the obstacles of genotypes and the low frequency of transformation still are the bottlenecks in this pathway. In maize genetic transformation at present, the Agrobacterium-mediated transformation and gene gun bombardment method are used the most widely. Compared with gene gun bombardment method, Agrobacterium-mediated transformation is not more difficult to operate, and can introduce large exogenous DNA fragments into receptor cell genome, and exogenous genes which have inserted in cell genome are usually in a single copy or two copies manner, and could stabile, inherited. In maize genetic transformation, good recceptor materials must have a strong ability of regeneration, high genetic stability and sufficient material sources, etc. At present, maize genetic transformation often use immature embryos, embryoinic calli and stem tips, etc. Among them maize immature embryos and shoot tips are applied most widely. Based on the mature system established in in our laboratory of Agrobacterium-mediated genetic transformation of maize shoot tips, the goal of the paper is mainly to compare the efficiency of different maize elite inbred lines in the transformation, and expect to find good inbred lines with strong regeneration ability and high transformation efficiency.Comparison of different maize inbred lines for transformation efficiencyFive maize elite inbred lines DH4866,6WC, Q319, Chang7-2 and Zheng58 were selected to transform with Agrobacterium-mediated pathway, and the efficiencies of the inbred lines were compared in each transformation stage in order to filter out the lines with strong regeneration ability and good transformation efficiency. In terms of the success rate of exposed shoot meristem and seedling survival percent, we concluded that Q319 inbred line is the best line, the second is DH4866 inbred line, the third is 6WC inbred line. In terms of the herbicide resistance, the transformated seedlings from inbred lines DH4866 and 6WC were compared for their herbicide resistance. The result showed that DH4866 inbred line had significantly higher ratio of plants showed the resistance to Basta in the transformated seedlings than that of 6WC.Observation of tassels and ears of TO transformated plants from different inbred linesObservation of tassels and ears of TO transformated plants from different inbred lines discovered that only the tassels of 6WC transformated plants were poorly development with few branches and less pollens among five inbred lines. The ears of transformated plants showed normal development and produced good kernels. Among them the transformated plants from 6WC showed less seed setting rate for there were more plants of empty stalk than that of DH4866 inbred line. The majority of transformated plants showed the characteristics of non-transformated plants of inbred transformated lines.PCR detection of T1 transformated linesIn this study there 27 different target genes were introduced into 5 different maize inbred lines with Agrobacterium-mediated transformation of maize shoot tips. Some of T1 lines derived from self-crossed transformated plants from DH4866 and 6WC inbred lines were conducted for herbicide screening and PCR detection. Among them DH4866 inbred line was detected a total of 110 lines, positive lines were 9 lines, so the transgenic rate was 8.2%; lines from 6WC were detected a total of 95 lines, positive lines were 3 lines, so the transgenic rate only was 3.2%.In summary, we have compared the five maize elite inbred lines by using the system of Agrobacterium-mediated genetic transformation of maize shoot tips, and the preliminary results indicated that the seedlings of DH4866 and Q319 inbred lines showed the best performance in this transformation system. |
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