External Application Of Amino Acids On Insecticidal Protein Content And Protein Cycle Of Reproductive Organ In Bt Cotton

Low insecticidal protein expression at reproductive organs affect insect resistance in Bt transgenic cotton,which has close relationship with Bt toxin level in square.flower and boll In order to enhance Bt protein concentration of the reproductive organs,the conventional cultivar Sikangl(S1)and the hybrid cultivar Sikang3(S3)were used as experimental materials;the combination applications of selected 5 and 21 types of amino acids respectively were sprayed on the reproductive organs during 2016,201 7 and 2018 cotton growing seasons The Bt protein contents,the chemicals and enzyme activity for protein synthesis and degradation of the square,flower and boll were investigation.the results showed that the square Bt protein contents increased by 7.4%to 19.4%compared to the control under the two amino acid treatments in both cultivars.and combination application of the 21 kinds of amino acids had more high Bt toxin level.Moreover,more reduction of square protein degradation resulted in more high Bt toxin level by combination application of the 21 type of amino acids.the flower Bt protein contents increased for the two amino acid treatments significantly in both cultivars,the Bt protein concentration increased by 15.2%to 25.8%in compared to the control.However,no significant difference were detected between the two treatments of amino acid applicationSimilar results of Bt toxin level observed in boll wall,cotton seed and fiber.The increase caused by the amino acid treatments on boll wall insecticidal protein contents at 25 DAFP were 7.4%to 9.30%for Cultivar S1,39.0 to 41.3%for cultivar S3 in two growth season;The amino acid application enhanced cotton seed Bt protein content by 23.9%to 71.1%for cultivar S1,15.8%to 53.8%for cultivar S3;Similarly,the increment of the fiber Bt protein content by 23.8%to 172%for cultivarS1,20.0%to 230.3%with sprayed amino acid.However,the differences of Bt protein content were not significant between the two amino acid treatments in the boll.Beside the flower protease and peptidase,increased amino acid and soluble protein contents,enhanced GPT and GOT activities,reduced protease and peptidase activities were observed by the amino acid application at the square,flower and boll.There was a significant positive correlation between Bt insecticidal protein content of square,flower and boll and GPT,GOT activities,amino acid,soluble protein content;Significant negative correlation between Bt toxin level and protease,peptidase activity.These results suggest that exterior combination application of the five amino acids which are main composition for the Bt protein can bolster the insecticidal level of reproductive organs.increased protein synthetic ability and reduced degradation ability were main physiological causes.