Molecular pyramiding of insect and glyphosate-resistant genes and correlation analysis on economic traits of the pyramided lines in upland cotton

Breeding cotton with simultaneous resistance to cotton bollworm and glyphosate can enhance the ability of resistance to insects and herbicides, reduce pest control and herbicide costs, and improve comprehensive economic productivity in cotton production. In this study, a hybrid population was developed using self-bred high-yield and high-quality upland cotton, domestic transgenic Bt cotton lines, and GR79+GAT transgenic upland cotton lines as parental hybrids. Non-glyphosate-resistant cotton seedlings were eliminated by applying 0.2% glyphosate in the seedling beds, and cotton plants were screened for resistance to cotton bollworm under field conditions without pest control. Specific primers were used in the laboratory to track the insect-resistant and glyphosate-resistant genes, and individual plants carrying the Bt and GR79+GAT genes were propagated into plant lines. Nine lines exhibiting resistance to both insects and glyphosate were obtained through field screening. Subsequently, the economic traits of the selected lines were compared and analyzed. Among these lines, strain BG-6 demonstrated the combined presence of insect-resistant and glyphosate-resistant genes, as well as higher lint yield and fiber quality. The fiber length, specific strength, and micronaire value of BG-6 were 30.9 cm, 30.1 cN tex^-1, and 4.9, respectively. Correlation analysis between yield traits and fiber quality traits revealed a negative correlation between lint percentage and uniformity index (<italic>r</italic> = -0.838^**), but no significant correlation was observed between other yield traits and fiber quality traits. In conclusion, our study successfully selected resistant cotton seedlings through glyphosate spraying in the seedling beds, identified resistant cotton plants under field conditions without pest control, detected two resistance genes using PCR in the laboratory, and evaluated high-yield and high-quality traits in the field. By following this approach, we achieved the pyramiding of multiple traits, including insect resistance, glyphosate resistance, and high-yield and high-quality characteristics, in the segregated progeny of comprehensive hybrid combinations.