Inheritance and expression stability of exogenous genes in insect-resistant transgenic poplar

Abstract

To understand the genetic and expression stability of transgenic insect-resistant poplar 741, this study compared the experimental plantations of transgenic insect-resistant poplar 741 lines (pb1, pb6, pb11, pb17, and pb29) with non-transgenic poplar 741, P. tomentosa Carr.f.yixianensis (poplar 84 K) and transgenic hybrid progeny lines cultured from immature embryos. The insect resistance and growth stability of transgenic poplar 741 were investigated by detecting exogenous genes by polymerase chain reaction (PCR), measuring the diameter at breast height (DBH) and volume growth, and performing insect-resistance tests against Clostera anachoreta and Hyphantria cunea. The inheritance and expression of the exogenous gene was also examined in transgenic hybrid progeny lines. The results revealed that the exogenous gene was stable, remaining stable in 8–10-year-old transgenic poplar 741 trees. No significant difference was found between the height of 10-year-old transgenic poplar 741 and non-transgenic poplar 741 in the experimental plantations in Baoding, China. The DBH and volume growth of pb17 was significantly greater than that of pb29 and pb11. The 8-year-old transgenic poplar 741 pb29 grown in Zhuozhou showed no significant difference from poplar 741 in terms of height growth, DBH, and volume. From 1999 to 2013, pb29-fed larvae (C. anachoreta larvae and H. cunea) exhibited stable mortality rates >79%. Likewise, pb11-fed larvae showed stable mortality rates (C. anachoreta larvae had mortality rates >75%, and H. cunea larvae exhibited rates >80%). pb17 conferred low insect-resistant stability, showing mortality rates that varied from 28.2 to 99.27% in C. anachoreta and H. cunea larvae. Among the hybrid progeny lines acquired by hybridization of pb1, pb29, and pb11 with 84 K poplar, the ratios of PCR-positive to PCR-negative lines for the BtCry1Ac gene were 1.31, 1.15, and 0.86, respectively. X 2 tests showed that the ratio was consistent with the Mendelian law of 1:1 segregation controlled by an allele pair. The hybrid progeny of pb6 × 84 K had a segregation ratio of 3:1. The nptII gene followed the same segregation rule as Cry1Ac. The transgenic hybrid progeny that contained Cry1Ac gene exhibited the same insect resistance as the parent plants.