Confirmation of a Paraquat Resistant Goosegrass (Eleusine indica) Biotype and Role of Retrotransposons in Paraquat Resistant Goosegrass

摘要

Diminished control of goosegrass was observed in papaya and bananas fields located in Panyu district of the city of Guangzhou, after years of repeated paraquat use. Resistance of the Panyu biotype was confirmed by its comparison with susceptible biotype. The underlying mechanism of resistance was also investigated. In fields of banana in 2005, applications of paraquat (0.6 kg ai/ha) reduced the dry weight of the Panyu biotype 18.6% of the reduction obtained from the control herbicide (Basta), and in 2007 only 12.3%. In papaya fields, the reduction decreased from 16% to 3.3% for the same years. In greenhouse experiments, the ED50 of the paraquat-treated putatively-resistant biotype was 1.29 kg ai/ha, which was significantly greater than another biotype known to be susceptible from that region, and also other biotypes collected from provinces further away in Guangxi, Shandong and Hubei. Since it is highly likely that the defense reactions of these plants against paraquat is probably attributable to genes that control ferritin production, PCR was conducted to amplify the ferritin genes from both resistant and susceptible goosegrass biotypes. A 713-bp cDNA sequence particular only to the resistant biotype was identified and amplified, and BLAST analysis of the corresponding protein indicated 100% homology between this sequence and 4 retrotransposon fragments (GenBank accession numbers AAL68845, XP_002438378, AAL75973 and XP_002442043). Therefore it might be that the mechanism leading to paraquat resistance in this biotype was triggered by a particular retrotransposon upon paraquat exposure, initiating a series of resistance reactions.