Objective Artificial hybridization was carried out using transgenic triploid 741 poplar with BtCry3A as the female parent and diploid Populus alba var. pyramidalis as the male parent, in order to quickly obtain new germplasm of aneuploid Populus tomentosa with insect-resistance.

Method Collecting female flower branches of transgenic 741 poplar and male flower branches of P. alba var. pyramidalis, hybrid progenies were obtained by embryo rescue technique from the inflorescence that was about to fall off. The seedlings with BtCry3A were identified by polymerase chain reaction, and further expression of BtCry3A was measured via real-time fluorescent quantitative polymerase chain reaction. Subsequently, conducted ploidy analysis of these hybrid progenies using flow cytometry method. Finally, preliminary phenotypic analysis of the offsprings was performed.

Result (1) Eight hybrid individuals were successfully generated by combing artificial hybridization and embryo rescue techniques, among which six hybrid offsprings showed good growth status. Five offsprings inherited the BtCry3A gene from the mother plants. (2) The BtCry3A gene exhibited enhanced expression levels in the offsprings compared with maternal parent, with individual 3# demonstrating a 12-fold increase. (3) 1# was hyper-tetraploid, 2#, 4# and 8# were aneuploid, while 3# may be aneuploid or tetraploid. (4) The hybrid offsprings exhibited diverse phenotype, the five hybrid individuals were different in leaf shape, leaf size and pitch spacing, with 3# and 8# showing superior growth vigor compared with parental lines.

Conclusion Employing artificial hybridization between triploid 741 poplar with BtCry3A and diploid P. alba var. pyramidalis, we creat the novel germplasms of aneuploid P. tomentosa with BtCry3A and diverse phenotypic variation. Offspring 3# has significantly higher anti-insect gene expression than their mothers, and growth potential is better than parents. It can be used as an excellent potential aneuploid hair poplar new germplasm for subsequent insect resistance tests.