Traditional breeding methods of crop breeding

(1) The breeding method of two parents crossing sexually and then selfing the first generation hybrid seeds is hybrid breeding, so the way shown in the direction of A→D in the figure represents hybrid breeding, and the breeding method of obtaining haploid plants from the first generation anthers in vitro and then treating the seedlings with colchicine to double their chromosomes is haploid breeding, so the way of A→B→C represents haploid breeding. The genotypes of the two parents are aaBB and AAbb respectively. These two pairs of genes are inherited according to the law of free combination, and the shortest way to cultivate new varieties of aabb genotype is A → B → C. Compared with these two breeding methods, the latter is homozygous, and there is no trait separation in self-bred offspring, so its advantages mainly lie in obtaining homozygotes quickly and shortening the breeding cycle.

(2)B is haploid breeding, and the common method is anther culture in vitro, that is, the anthers produced by meiosis of hybrid seeds are cultured in plant tissues to obtain haploid plants. Process C is to treat haploid seedlings with colchicine, and process F is to treat germinated seeds or seedlings with colchicine. Its principle is that it can inhibit the formation of spindle during cell mitosis, thus doubling the number of chromosomes in cells.

(3) E in the figure is usually irradiated with various rays or treated with nitrous acid. This breeding method is mutation breeding, and the genetic principle used is gene mutation.

(4) The process shown in g can adopt the pollen tube pathway method, and the bioengineering technology involved in this process is genetic engineering.

(5) A, D and G used the principle of gene recombination in the above breeding process.

(6) The process shown in g can adopt the pollen tube pathway method, which is the step of introducing the target gene into the recipient cell in the "four steps" of genetic engineering operation. In addition, genetic engineering has three steps, namely, extracting the target gene, combining the target gene with the vector, and detecting and identifying the target gene.

So the answer is:

(1) hybrid haploid obviously shortens the breeding cycle.

(2) In vitro culture of anther colchicine

(3) Gene mutation

(4) genetic engineering or DNA splicing technology or DNA recombination technology or transgenic technology.

(5)A、D、G

(6) introducing the target gene into the recipient cell, extracting the target gene, combining the target gene with the vector, and detecting and identifying the target gene.