However, our 2-year experiments plus that in 2003 (Chen et al.,
2006) also demonstrated a reduced field performance of the three
insect-resistant GM rice lines under extremely low insect pressure
regarding the yield-related traits, especially under the mixed
cultivation condition with competition that can enlarge the differences
between GM rice lines and their non-GM control. The reduced
yield performance was most likely caused by the underlying cost of
the insect-resistance transgenes, particularly in the Bt/CpTI doubletransgene
GM lines under competition, because the three GM lines
were selected from hundreds of transgenic lines with good agronomic
traits. In this case, the yield advantage of insect-resistantGM
rice may not be realized when the pressure of target insects in the
fields is insufficient, as indicated by our yield results of the experiment
in 2004. It is however necessary to point out that there was
a certain degree of decrease in yield-related traits in both GM and
non-GM rice lines at the site under low insect pressure, compared
to that under normal insect pressure. This was most likely caused
by the slightly poor soil condition on the rooftop plots, in comparison
with that in the field plots (normal insect site). However,
the observed decrease in yield traits at the low insect site will not
affect our general findings concerning the yield benefit and cryptic
cost because our results were obtained through comparison of
the yield-related traits of GM and non-GM plants within the same
environment (site).
However, our 2-year experiments plus that in 2003 (Chen et al.,
2006) also demonstrated a reduced field performance of the three
insect-resistant GM rice lines under extremely low insect pressure
regarding the yield-related traits, especially under the mixed
cultivation condition with competition that can enlarge the differences
between GM rice lines and their non-GM control. The reduced
yield performance was most likely caused by the underlying cost of
the insect-resistance transgenes, particularly in the Bt/CpTI doubletransgene
GM lines under competition, because the three GM lines
were selected from hundreds of transgenic lines with good agronomic
traits. In this case, the yield advantage of insect-resistantGM
rice may not be realized when the pressure of target insects in the
fields is insufficient, as indicated by our yield results of the experiment
in 2004. It is however necessary to point out that there was
a certain degree of decrease in yield-related traits in both GM and
non-GM rice lines at the site under low insect pressure, compared
to that under normal insect pressure. This was most likely caused
by the slightly poor soil condition on the rooftop plots, in comparison
with that in the field plots (normal insect site). However,
the observed decrease in yield traits at the low insect site will not
affect our general findings concerning the yield benefit and cryptic
cost because our results were obtained through comparison of
the yield-related traits of GM and non-GM plants within the same
environment (site).
การแปล กรุณารอสักครู่..
