SSR Marker-Assisted Breeding For Transgenic Bt Cotton

Two backcross populations were built, with JR-1as the donor parent of transgenic Bt gene, and two receptor parents Bll and Jing15which had good performance in agronomic traits. The exogenetic Bt gene (CrylAb/Ac) was selected by Kanamycin identification on the plant leaves in the field and specific PCR amplification of Bt or NPT II gene. The background selection was based on the random SSR markers or performance of plants in the field. The purpose of the paper was to get purified Bt lines with excellent agronomic performance.The main results were as following:1. The plants resistant to Kanamycin were indentified in the two BC2F1populations as the foreground selection. The results showed that the segregation ratio of positive and negative plants was0.12and0.15(P>0.05) respectively with the Chi-square test, which was consistent with Mendel’s law of segregation. It was also coincided with detection of PCR amplification of gene NPT II. Specific fragment of Cry IAb/Ac gene were amplified in homozygous lines of BC2F3, which were derived from the two backcross combinations.2. Three homozygous lines was selected with Bt gene from combination of B11×JR-1which had the similar genetic background of Bll. The rate of genetic background recovery was91.94%-96.77%, with the average of94.09%, which was6.59%higher than the theoretical values. Four homozygous lines was selected with Bt gene from combination of JingI5xJR-1. The rate of genetic background recovery was93.55%-96.77%, with the average of95.16%, which was7.66%higher than the theoretical values. Molecular marker-assisted selection could select the genetic background recovery quickly, because the background recovery ratios of the7homozygous lines were all much higher than theoretical values.3. There were no significant difference between the3homozygous strains from the BllxJR-1combination and the parent Bll in fiber quality, but there were there were significant differences in yield, on the boll weight and single boll weight in some strains, some were better or worse than recurrent parent. There were no significant differences between the4homozygous strains of the JingI5xJR-1and parent Jing15in yield, but some differences was detected significantly on the lint percentage, micronaire and elongation in individual lines. In general, the7selected strains in only a few strains on a few traits had significant difference with the recurrent parent, illustrate the backcross improved strain in most of the characters and the recurrent parent had higher consistency.4. Compared with the recurrent parent, the variation of7homozygous selected strains were uncertain in yield, yield components, or fiber quality. The performance of agronomic or fiber traits were not determined completely by the genetic background recovery. Therefore, the traditional selection in the field should be emphasized for better selection effect, as well as the molecular marker-assisted selection.5. The boll worm resistances of7homozygous strains were evaluated by indoor method. The results showed that the all Insect-resistant homozygous strain resistance to boll worm in cotton leaves of mortality rate were lower than the donor parent of JR-1, except for the A4-4larva mortality rate was lower than the sense of contrast Bll, other larva mortality rates in the rest of the strain were higher than the combination of insect control. Most of the selected cotton bollworm resistances performance of strains were belong to the low resistance type, only the resistance performance of B22-1close to the donor parent of JR-1, belong to the type of resistance. The selected strains was difficult to applied in production because the average performance in insect-resistance.