AUTHOR=Ren Yachao , Zhang Jun , Wang Guiying , Liu Xiaojie , Li Li , Wang Jinmao , Yang Minsheng 

TITLE=The Relationship between Insect Resistance and Tree Age of Transgenic Triploid Populus tomentosa Plants

JOURNAL=Frontiers in Plant Science

VOLUME=9

YEAR=2018

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2018.00053

DOI=10.3389/fpls.2018.00053

ISSN=1664-462X

ABSTRACT=<p>To explore the stability of insect resistance during the development of transgenic insect-resistant trees, this study investigated how insect resistance changes as transgenic trees age. We selected 19 transgenic insect-resistant triploid <italic>Populus tomentosa</italic> lines as plant material. The presence of exogenous genes and Cry1Ac protein expression were verified using polymerase chain reaction (PCR) and enzyme-linked immunosorbent assay (ELISA) analyses. The toxicity for <italic>Clostera anachoreta</italic> and <italic>Lymantria dispar</italic> was evaluated by feeding fresh leaves to first instar larvae after the trees were planted in the field for 2 years and after the sixth year. Results of PCR showed that the exogenous genes had a long-term presence in the poplar genome. ELISA analyses showed significant differences existed on the 6-year-old transgenic lines. The insect-feeding experiment demonstrated significant differences in the mortality rates of <italic>C. anachoreta</italic> and <italic>L. dispar</italic> among different transgenic lines. The average corrected mortality rates of <italic>C. anachoreta</italic> and <italic>L. dispar</italic> ranged from 5.6–98.7% to 35.4–7.2% respectively. The larval mortality rates differed significantly between the lines at different ages. Up to 52.6% of 1-year-old transgenic lines and 42.1% of 2-year-old transgenic lines caused <italic>C. anachoreta</italic> larval mortality rates to exceed 80%, whereas only 26.3% of the 6-year-old transgenic lines. The mortality rates of <italic>L. dispar</italic> exhibited the same trend: 89.5% of 1-year-old transgenic lines and 84.2% of 2-year-old transgenic lines caused <italic>L. dispar</italic> larval mortality rates to exceed 80%; this number decreased to 63.2% for the 6-year-old plants. The proportion of 6-year-old trees with over 80% larval mortality rates was clearly lower than that of the younger trees. The death distribution of <italic>C. anachoreta</italic> in different developmental stages also showed the larvae that fed on the leaves of 1-year-old trees were killed mostly during L<sub>1</sub> and L<sub>2</sub> stages, whereas the proportion of larvae that died in L<sub>3</sub> and L<sub>4</sub> stages was significantly increased when fed on leaves of 6-year-old trees. Results of correlation analysis showed there was a significant correlation between the larvae mortality rates of trees at different ages, as well as between Cry1Ac protein contents and larvae mortality rates of 6-year-old trees.</p>