Abstract：The transformation method via pollen-tube pathway has great potential roles in crop molecular breeding. In this paper, the effects of genotype, exogenous DNA concentration injected, and the flower positions in plant on cotton genetic transformation mediated by pollen-tube pathway were evaluated. It was found that there were no obvious differences on the boll setting rate and transformation efficiency between the cultivars 33B and 99B. However, the DNA concentrations and the flower positions largely affected the transformation efficiency. The putative transgenic plants derived from boll seeds injected with binary expression vector pCAMBIA3301 DNA were all to be PCR positive. On the other hand, the expression levels of reporter gene Gus varied dramatically, including high, middle, and nontranscripts detected. Both the GUS activity of the transgenic plants and the intensity of histochemical GUS staining in the representative transgenic plants were in accordance to those of the transcripts of reporter gene Gus. The selection of high quality and suitable concentration of exogenous DNA and the injection of the DNA in basal flowers at the middle fruit branches are important factors for improving the cotton transformation efficiency. The transformation method via pollen-tube pathway established in this study has provided an efficient genetic transformation technique in cotton breeding.
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