Selective Action Mechanism of Fenclorim on Rice and Echinochloa crusgalli Is Associated with the Inducibility of Detoxifying Enzyme Activities and Antioxidative Defense

Fenclorim (Fen) is a safener developed
for pretilachlor (Pre) that
can protect rice from injury caused by Pre but does not lower the
weed control effects of Pre. Unfortunately, the mechanism of selective
action of Fen between rice and weeds, such as Echinochloa
crusgalli (barnyard grass), has not been clarified.
In this study, the differences in physiology, biochemistry, and gene
transcription between rice and E. crusgalli response to Fen were compared. Comparing the protection effects
of Fen on plant growth, it was found that Fen significantly protected
rice from Pre, but did not protect E. crusgalli. The detection of malondialdehyde (MDA) content and activities of
antioxidant enzymes showed that Pre induced significant oxidative
damage both in rice and E. crusgalli; however, Fen reduced oxidative damage in rice but not in E. crusgalli. Transcriptome analysis revealed that
Fen induced more genes related to herbicide metabolism in rice than
in E. crusgalli, especially the glutathione-S-transferase
(GST) genes, with six upregulated in rice but no genes upregulated
in E. crusgalli. Accordingly, the GST
activity analysis showed that Fen increased the activity of rice instead
of E. crusgalli. These results indicate
that the elevation of detoxifying enzyme activities and antioxidative
defense may be the mechanism of selective action of Fen in rice but
not in E. crusgalli.