Application Of Transgene Stacking In Breeding Of New Cotton Varieties

Transgenic technology has played important roles in the directional improvement of Plant traits and creation of innovational and special breeding materials. Combining of genetically modified technology with conventional breeding techniques will be the future direction of cotton breeding program, because of the narrow resources of the cotton germplasms. Twelve hybrid combinations were made by top-cross with 13 different transgenic lines which had the same genetic background of a receptor variety (Huakangmian No.1) in the transformation experiment, including four transformants of rolB gene, three transformants of mannosyltransferase gene, three transformants of mnxoxygenase gene, and three lines separately generated with three constructs of transposon activation tagging.All the hybrid combinations together with five parental lines, one check test variety (hybrid Eza No.23) in total 18 materials were put in trial for evaluating of the effect of transgene stacking and the feasibility of the transgene stacking strategy applied in cotton breeding program. The trial was arranged in accordance to the design of randomly grouped plots and three times repeats.The main results were as following:1. The total DNA was extracted from the leaves of transgenic and control plants for polymerase chain reaction (PCR) analysis. A same anticipated fragment was amplified from the plants of all transgenic lines and the positive control plasmid DNA, but no positive signal was observed from the negative control plants, indicating that these transgenes were kept stable in the genome of the transgenic lines in higher generations.2. The results also showed that (1) the cotton yields of four combinations with stacked transgenes were increased by 17%～31%, the differences reached an extreme significant level statistically, while compared with those of their parental lines. (2) The biggest averaged boll weight of F₁ combinations with stacked transgenes reached 6.8g. The averaged boll weights of four F₁ combinations reached statistically extreme significant level, compared with that of their paternal line, but did not reach significant level while compared with those of their maternal lines. (3) The lint percentages in three of the four combinations reached 43.2%, 42.2% and 41.4% separately. (4) The boll number of per plant was extremely improved in the combination 7020×7021, in which it increased by 20.8% while compared with the parental line. The boll number of per plant had greatly improved by transgenic stacking. (5) The plant heights of the cross- pollinated combinations were fallen between those of the two parents. The numbers of effective fruit branches of the four F₁ combinations with stacked transgenes did not show significant differences, compared with their parental lines. (6) The fiber lengths (UHML) were located from 28.55 to 30.1mm in four F₁ combinations, longer than those of their parental lines, but the differences did not reach significant level. The fiber uniformities were improved and fallen in 84.90%～86.10%. No significant modifications were detected in fiber Micronae, elongation percentage and strength.3. Except the combination of the lines of ms2P-mant-gus and ms2P-mant-gus & Bt, of which the seed cotton yield was lower than that of the control variety "Erza 23", the other 11 participants with stacked transgenes all had higher output in seed cotton yield than that the control had. The seed cotton yield of the combination of En-DS and ms2P-mant-gus & Bt was higher 23.2% than that of the control, and the difference reached a extreme significant level statistically. The yields of the combinations of three transgenic lines of 35S-rolB and the line of ms2P-mant-gus & Bt, were increased by 18%, 17.3% and 13.8% each. All indexes in fiber quality of the combinations were equivalent to those of the control hybrid "Erza 23", no significant differences were detected, but these met the requirements of agricultural production.