农业分子育种 授粉后外源DNA导入植物的技术

 一个外源DNA导入植物的技术已在我国棉花和水稻育种上应用多年，成功地转移了不同来源的抗病或其它性状基因。由此得到的稳定遗传新品系在大田中已繁殖7-10代，有的已扩种200公顷。应用这一技术使供体DNA片段加入到栽培种的基因组中，育成一个新品种只需要3-4代，比常规育种6-8代的时间缩短一半。这一技术的要点是：授粉后使外源DNA能沿着花粉管经过的珠心通道进入胚囊，转化尚不具备正常细胞壁的卵、合子或早期胚胎细胞。转化率可高达10#+（-2），不需要原生质体的制备、细胞培养和再生植株。所用的DNA系带有目的基因的供体总DNA片段（10#+6-10#+7道尔顿）。这一技术的原理可以应用于任何开花植物。但针对不同植物的具体技术细则必需根据植物的花器结构以及授粉受精时间和过程来决定。这一生物工程技术简单，育种工作者容易掌握，而且任何基因源都可能用来进行基因转化，只要基因的结构与受体基因组相容，基因的产物能适应受体植物的代谢。应用这一技术就能筛选出有用的基因改良品种。

MOLECULAR BREEDING OF AGRICULTURE A TECHNIQUE FOR INTRODUCING EXOGENOUS DNA INTO PLANTS AFTER SELF POLLINATION

A technique for introducing exogenous DNA into plants has been applied to breed cotton and rice in China for several years. Genes responsible for disease resistance and other traits from different sources have been successfully transformed. Stabilized varieties thus obtained have been cultivated in the field for 7 to 10 generations. Some of them have already been extended to 200 hectare lots. By means of this technique the segments of DNA from donor were added to the genome of cultivars. It was found that only 3 to 4 generations were needed to breed a new variety instead of 6 to 8 generations for conventional crossing.The technique is briefly as follows: After self pollination, the exogenous DNA is allowed to pass along the pathway of the pollen tube in the nucellus to enter the embryonic sac and transform the egg, zygote or early embryonic cells. The cell or cells to be transformed in that time do not have normal cell walls. The transformed seed then the plant could be obtained directly. The transformation rate could be as high as 10~(-2) . No protoplast preparation, cell culture or plant regeneration is needed. The DNA used is the total DNA segments (10~6-10~7 daltons) of the donor which carried the goal gene (s). This technique can be applied in principle to any flower plant. For a definite species, the details of the technique should vary in accord with the characteristics of the species. Different species of plants have different flower structures and also show differences in time and duration of pollination and fertilization.Since this biotechnique is simple, breeders take it up easily. It is a promising technique by which any gene source may be used for transformation when the gene structure is compatible with the recipient plant genome and the gene product fits into the metabolism of the plant. Using this technique useful genes can be screened for advancement in varieties.