| Thirteen hybrid combinations were made with eleven different transgenic lines which had the same genetic background as that of the transformation receptor variety (Huakngmian No.1), including one transgenic line of rolB gene, five lines of monooxygenase gene, two lines of mannosyltransferase gene (mant), one line of bt/mant construct, one mutant with giant bolls induced by transposon activation tagging, one line of bt/bar/Ds construct. All combinations together with six transgenic parental lines, one transformation receptor variety and one check test variety (hybrid Eza No.23) in a total of twenty one 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 according to the design of randomly grouped plots and three times repeats. Furthermore, the transgenic lines, which showed higher ability of Bemisia tabaci resistance in the trial, were further evaluated for their resistance to Bemisia tabaci in field in the next year.The main results were as following:1.The results of transgene stacking showed that (1) multi-transgene stacking can increase the cotton yield significantly. The yield increments in seed cotton of two combinations with stacked transgenes attained 27.70% and 14.90% separately, the differences reached significant level statistically compared with those of their parental lines. (2) The boll number of per plant can be increased by multi-transgenic stacking. The boll number of per plant in one of the combinations with stacked transgenes was increased by 33.35%; the differences reached an extreme significant level statistically while compared with those of their parental lines. (3) The fiber quality of the combinations has a trend toward that of the parental transgenic line that has better fiber quality, and does not show the vigor over better parents. (4) The combinations stacked with mant transgene showed a higher resistibility to carmine spider damage. Four among five combinations showed a lower damage severity index, compared with their parental lines. The degrees of decrements in damage severity index varied from 0.73% to 3.36%. 2. Multi-transgene stacking is an effective way of developing fine cotton varieties with high-yield and fine fiber quality. In this study, excepting one (7452×7028) that has a lower cotton yield than that of a popularized hybrid "Eza23", among thirteen combinations, seven showed an extreme significant increment in the yields of seed cotton, the competitive advantages (CA) varied from 15.06% 24.97%, and five showed an extreme significant increment in ginned cotton. Two combinations showed a significant increment in seed cotton yield. The combination 7028×7013 occupies the top place in seed cotton yield in the experiment, the CA is 24.97%. The combinations placed at second and third positions are 7329×7028 and 7449×7015; the percentages of yield increment in seed cotton are 23.78% and 21.06% separately compared with the control hybrid.3. Seven transgenic lines, including two lines of ms2P-Mant, one line of Bt/Mant, two lines of 4En/ms2P-Mnx and two lines of rolB, were selected to investigate cotton whitefly (Bemisia tabaci) resistance. The results showed that only the Bt/Mant transgenic line has a stronger resistibility to whitefly damages than the control "Huakngmian No.1" does. This line showed the highest resistibility than that of other transgenic lines, and was basically not damaged by the insects. The rolB transgenic lines have a lowest resistibility and were seriously damaged by the insects in the year of 2008. |
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